WO2019027188A1

WO2019027188A1 - Magnesium alloy sheet and manufacturing method therefor

Info

Publication number: WO2019027188A1
Application number: PCT/KR2018/008565
Authority: WO
Inventors: 김상현; 권오덕; 채영욱; 김재중
Original assignee: 주식회사 포스코
Priority date: 2017-08-03
Filing date: 2018-07-27
Publication date: 2019-02-07

Abstract

The present invention relates to a magnesium alloy sheet and a manufacturing method therefor. The magnesium alloy sheet can comprise, on the basis of a total 100 wt%: zinc (Zn) in an amount greater than 0 and less than or equal to 2.0 wt%; manganese (Mn) in an amount greater than 0 and less than or equal to 1.0 wt%; cerium (Ce) in an amount greater than 0 and less than or equal to 0.5 wt%; and the balance of magnesium (Mg) and other inevitable impurities.

Description

[Specification】

Title of the Invention

Magnesium alloy sheet and manufacturing method thereof

TECHNICAL FIELD

The present invention relates to a magnesium alloy sheet and a method of manufacturing the same.

TECHNICAL BACKGROUND OF THE INVENTION

In recent years, light weight (gram, gram) marketing has been actively performed in mobile and IT fields. More specifically, as the functions of the mobile device field are diversified, a light weight material is required. As a result, there is an increasing interest in magnesium sheets having excellent non-strength (strength against density).

The density of magnesium is 1.74 g / cin ³ , which is the lightest among structural metals including aluminum and steel. In addition, it is a metal that is popular in mobile and IT fields due to its excellent vibration absorbing ability and electromagnetic shielding ability. In addition,

In the field of advanced countries with Europe as the leading fuel economy regulations and to improve the performance of the weight of the car body weight is being actively under research, and magnesium is being spoken as a metal.

However, since magnesium is expensive compared to competitive materials such as aluminum and stainless steel, its application is limited to only some parts that are required to be lightweight.

In addition, since magnesium has hexagonal close packing (HCP), it is difficult to mold at room temperature. In order to be applied to a product, a molding process is indispensable, so that a large amount of investment for mold / heating device for warm molding may occur. In addition, there is a characteristic that sticking phenomenon between the mold and the material, scratching, and heating takes time and productivity is lowered. In addition to the price of magnet materials, the processing cost of magnesium alloys is also more expensive than competitive materials.

In addition, even if the basic formability is excellent, the difference in formability between the rolling direction (RD) and the width direction (TD) of the plate material becomes greater when the internal microstructure has center segregation or coarse intermetallic compounds are aggregated. Thus, there arises a problem that the deviation of physical properties is increased. In addition to formability, corrosion resistance This is a major factor impeding the expansion of the magnesium alloy market. The magnesium alloy rapidly corrodes when exposed to atmospheric air or moisture, and therefore expensive surface treatment is required for use in such applications. To overcome these drawbacks, we have developed high corrosion resistant alloys,

It has disadvantages in that it only improves the corrosion resistance and the moldability is poor.

Therefore, in order to be used as a processing material for automobile and IT

In addition to corrosion resistance, room temperature moldability should also be improved.

DISCLOSURE OF THE INVENTION

[Problem to be solved]

An object of the present invention is to provide a magnet alloy sheet material excellent in room temperature moldability, anisotropy and corrosion resistance and a method for manufacturing the same.

Specifically, the content and relationship of Zn, Mn, and Ce components can be controlled to control impurities and secondary phases of the magnesium alloy sheet material. From this, it is possible to provide a magnet alloy sheet material excellent in corrosion resistance, moldability, and anisotropy. [MEANS FOR SOLVING PROBLEMS]

The magnesium alloy sheet according to one embodiment of the present invention has a zinc (Zn) content of more than 0 to 2.0 wt%, a manganese (Mn) content of more than 0 to 1.0 wt%, a cerium (Ce) %, Residual magnesium (Mg), and other unavoidable impurities.

The magnesium alloy sheet material may satisfy the following relational expression (1).

[Zn] > [Mn] + [Ce]

Here, [Zn], [Mn], and [Ce] refer to weight percent of each component.

The other unavoidable impurities may include Al: 0.3 wt% or less and Fe: 100 ppm or less.

The thickness ratio of the center segregation to the thickness of the magnesium alloy sheet material may be 10% or less.

The average particle size of the Mg-Ce phase and lower phase is 0. To 20 / m, and 1 to 30 per 100 ² of the magnesium alloy sheet material.

The average grain size of the Mn-based secondary may contain one or more sugar卿1 to 15, the area 100 / of the magnesium alloy plate and m ^2. The base aggregate maximum aggregate strength of the magnet alloy sheet material may be 1 or more and 4 or less.

The magnesium alloy sheet may have an Erickson value at room temperature of 7 to 11 mm.

The magnesium alloy sheet material may have a corrosion rate of 2.0 / / y or less.

The magnesium alloy sheet material may have a critical bending radius value at room temperature of 4 R / t or less.

The magnesium alloy sheet may have a limit bending radius value at 200 ^o C of 1.5 R / t or less.

The magnesium alloy sheet material may have a difference between the rolling direction (RD) and the plate material width direction (TD) by 0.5 R / t or less.

The cerium may be either a cerium element alone or a cerium-

May be included in the form of mi metal.

The mis-metal may further include other rare earth elements.

(Mn) is more than 0 and not more than 1.0 wt%, cerium (Ce) is not more than 0 and not more than 2.0 wt%, and manganese ) Comprises a step of preparing a cast material by casting a molten alloy containing from 0 to 0.5% by weight, the balance being magnesium (Mg) and other unavoidable impurities, subjecting the cast material to homogenization heat treatment, Hot rolling to prepare a rolled plate material, and finally heat-treating the rolled plate material.

The molten alloy of the alloy could satisfy the following relational expression (1).

[Zn] > [Mn] + [Ce]

At this time, [Zn], [Mn], and [Ce] refer to weight of each component. The other gross-smelling impurities may include Al: 0.3 wt% or less and Fe: 100 ppm or less.

The step of subjecting the cast material to a homogenizing heat treatment may be performed at a temperature of 300 ° C

Lt; RTI ID = ^0.0 > 500 C. < / RTI >

The step of homogenizing the cast material is performed for 1 to 30 hours .

Specifically, the step of subjecting the cast material to homogenization heat treatment may include a first homogenization heat treatment step and a second homogenization heat treatment step.

The primary homogenizing heat treatment is also 300 degrees ⁽⁰ C) to 400 may be live-action in (° C). Specifically, it may be carried out for 0.5 to 10 hours.

The second homogenization heat treatment may be carried out 400 degrees ⁽⁰ C) to about 500 in FIG. (° C). Specifically, it may be carried out for 0.5 to 20 hours.

The step of hot-rolling the homogenized heat-treated cast material to prepare the rolled plate may be performed at a temperature of 150 ° C to 400 ° C.

Specifically, it can be carried out at a rolling reduction of not less than 0 and not more than 40% per rolling.

The step of rolling the homogenized heat-treated cast material to prepare a rolled plate may further include intermediate-annealing the rolled plate.

The intermediate annealing is performed at least once during the warm rolling of the rolled sheet material twice or more, and the cumulative rolling reduction of the rolled sheet material may be 40% or more.

In the step of intermediate annealing the rolled sheet material, the intermediate annealing execution rate may be 20% or less.

The intermediate annealing may be performed 300 degrees ⁽⁰ C) to about 500 in FIG. (° C). The intermediate annealing may be conducted for 5 hours or less (excluding 0 hours). The step of final annealing the rolled sheet can be carried out 250 degrees (° C) to 500 in Figure ⁽⁰ C).

Specifically, it may be conducted for 5 hours or less (excluding 0 hours).

【Effects of the Invention】 ,

According to an embodiment of the present invention, it is possible to provide a magnesium alloy plate excellent in room temperature moldability and corrosion resistance by adding a small amount of Mn and Ce to a Zn-based magnesium alloy and controlling the production step.

Specifically, the impurities and the secondary phase (intermetallic compound) of the magnesium alloy sheet can be controlled by controlling the content and relationship of Zn, Mn, and Ce. From this, it is possible to provide a magnesium alloy sheet material excellent in corrosion resistance. Further, it is possible to provide a magnesium alloy sheet material excellent in moldability by dispersing the bottom surface texture. In addition, by controlling the center segregation of the secondary phase, it is possible to provide a magnesium alloy plate excellent in anisotropy.

BRIEF DESCRIPTION OF THE DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a photograph of a microstructure of the microstructure after (a) and (b) after homogenization heat treatment in Example 2 and Comparative Example 4 under an optical microscope.

2 is a photograph of the composition analysis of each intermetallic compound analyzed by scanning electron microscopy (SEM) and backscattered eletron (BSE) images using SEM-EDS .

3 is a graph showing the results of a salt water immersion test (Sal t

Immers ion test) and the corrosion product is removed.

Fig. 4 is a comparison of the {0001} XRD pattern of the embodiment and the comparative example.

FIG. 5 is a photograph of the {0001} XRD pattern and EBSD of Example 2 and Comparative Example 5. FIG.

FIG. 6 is a graph showing the results of V-bending test at room temperature (a) and 200 ° C (b) of Example 2, showing microstructure in the direction of RD (Rolling Diode) Was observed with an optical microscope.

DETAILED DESCRIPTION OF THE INVENTION

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. However, it is to be understood that the present invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. It is intended that the disclosure of the present invention be limited only by the terms of the appended claims. Like reference numerals refer to like elements throughout the specification.

Thus, in some embodiments, well-known techniques are not specifically described to avoid an undesirable interpretation of the present invention. Unless defined otherwise, all terms (including technical and scientific terms) used herein And may be used in a sense commonly understood by those having ordinary skill in the art to which the present invention belongs. Whenever a component is referred to as " including " an element throughout the specification, it is to be understood that the element may include other elements, not the exclusion of any other element, unless the context clearly dictates otherwise. Also, singular forms include plural forms unless the context clearly dictates otherwise.

The magnesium alloy sheet according to one embodiment of the present invention may contain zinc (Zn) in an amount of 0 to 2.0 wt% or less, manganese (Mn) in an amount of 0 to 1.0 wt% or less, cerium (Ce) in an amount of 0 By weight, up to 0.5% by weight, residual magnesium (Mg) and other unavoidable impurities.

At this time, the magnesium alloy sheet material may satisfy the following relational expression (1)

[Zn] > [Mn] + [Ce]

Here, [Zn], [Mn], and [Ce] refer to weight percent of each component.

As for the magnesium alloy sheet material, the content of the Zn component may be larger than the sum of the Mn and Ce components, as in the relational expression (1). When the relationship is limited as in the above-mentioned relational expression (1), the magnesium alloy sheet material may have a good rolling property and moldability.

As will be described later, manganese serves to control impurities such as iron (Fe) and silicon (Si). Therefore, when manganese is contained in the above range, the content of impurities contained in the magnesium alloy sheet material can be effectively reduced owing to the above-described characteristics.

Specifically, the Fe content in other unavoidable impurities contained in 100 weight ¾ of the magnesium alloy sheet as a whole may be 100 ppm or less. Also, the A1 content was

0.3 weight < 3 > > or less. However, the kind of the impurity is not limited thereto, and may include other unavoidable impurities.

As described above, by controlling the content of the impurities to a small extent, the corrosion resistance, rolling property and moldability of the magnesium alloy sheet material can be improved.

In addition, the magneto-alloy plate according to one embodiment may further include aluminum (A1). Aluminum may be included in an amount of 0.3% by weight or less based on the entire magnesium alloy sheet material. The composition range of the aluminum component is not particularly limited,

In a magnesium alloy sheet according to an embodiment of the present invention, May be added to the impurity level as compared to the additive element.

Hereinafter, the reasons for limiting the composition and composition of the magnesium alloy sheet according to one embodiment of the present invention will be described in detail.

The zinc (Zn) may be contained in an amount of more than 0 to 2.0% by weight, preferably 0.5 to 2.0% by weight, more preferably 0.5 to 1.6% by weight.

When zinc is added in an amount of more than 2.0% by weight, zinc binds with magnesium and / or cerium to produce a large amount of additional intermetallic compounds and makes existing intermetallic compounds and / or additional intermetallic compounds coarser, And local corrosion may occur in such a coarse intermetallic compound, which may degrade corrosion resistance. In addition,

Stitching may become severe and difficulties may occur. Accordingly, when the zinc is contained in the above-mentioned range, an effect of improving room temperature moldability and corrosion resistance can be expected.

When added together with rare earth elements, zinc may segregate in the grain boundaries and the twin-crystal systems to contribute to the generation and growth of the non-bottom-grain recrystallized grains. As a result, softening phenomenon of the bottom surface is brought about, and the slip of the bottom surface is activated to improve the formability of the plate material.

The manganese (Mn) may be contained in an amount of more than 0 to 1.0 wt%

Preferably 0.2 to 1.0% by weight.

Manganese is a recrystallized nucleation site, which produces fine grains and then serves to inhibit grain growth and provide fine and uniform grains. The magnesium alloy sheet, which is another embodiment of the present invention to be described later,

It is possible to provide fine crystal grains in the homogenizing heat treatment step of the manufacturing method and finely control the crystal grains of the final magnesium alloy sheet material.

When manganese is contained in the above-mentioned content range, since the crystal grains of the homogenized heat treated plate are finely controlled, it is possible to prevent defects such as abnormal grain growth and orange peel due to shear band in the warm rolling step and surface cracks . The rolling property of the magnesium alloy sheet according to one embodiment can be easily achieved. When manganese is contained in the above-mentioned content range, iron (Fe), It is possible to control impurities such as silicon (Si) and the like, whereby the corrosion resistance of the magnesium alloy sheet material can be improved. By providing a plate material having fine crystal grains through addition of manganese, both strength and formability can be excellent.

When manganese is contained in an amount exceeding the above-mentioned content range, the rolling property is deteriorated and a dispersed type crack is generated on the surface, so that it may not be possible to produce a plate having the corresponding thickness. The magnesium alloy sheet material may include cerium (Ce), for example, the cerium element may be contained singly or in the form of mi metal (mi schmet al). When included as micro metal, the mis-metal may further include rare earth elements such as La, Nd, Pr or a combination thereof.

The cerium may be contained in an amount of 0 to 0.5 wt% or less, preferably 0 to 0.2 wt% or less, based on the magnet alloy sheet material.

When cerium is added together with zinc, it contributes to the formation and growth of the non-bottom side recrystallized grains, causing softening of the bottom side,

Thereby improving the moldability of the plate material. When cerium above the above range is added, it is combined with magnesium and / or zinc to form a large amount of intermetallic compound and make it coarse, which may hinder rolling property, formability and corrosion resistance.

The magneto-alloy plate according to an embodiment of the present invention may have a ratio of the thickness of the center segregation to the total thickness of the magneto-alloy plate, which is less than 10¾. At this time, the center segregation thickness ratio = (center segregation thickness / final plate thickness) X 100 may be used.

Specifically, when the thickness ratio of the center segregation is in the above range, the anisotropy, which is the difference in physical properties between the rolling direction RD and the plate material width direction TD, can be reduced. The center segregation can be reduced as described above by controlling the alloy, its components, and the composition range. Specifically, it may be a result of controlling the composition and the composition range of the alloy so as to form the secondary phase (intermetallic compound) and the segregation to a minimum, and controlling the conditions to homogenization heat treatment and rolling (intermediate annealing).

Specifically, when the ratio of the thickness of the center segregation to the total thickness of the magnet alloy plate is 10% or less, it means that core segregation is hardly formed. Accordingly, when the center segregation in the magnet alloy plate material is in the above range, Anisotropy of the magneto-alloy plate material may be excellent.

Herein, anisotropy in the present specification means that the properties of the magnesium alloy sheet material are different depending on the orientation. Specifically, the rolling direction RD and the plate width

And the physical properties in the direction (TD) are different.

Therefore, when the thickness ratio of the center segregation is in the above-mentioned range, the anisotropy of the magnet alloy sheet material can be excellent. Also, in this specification, anisotropy

Excellentness means that the difference in physical properties between the rolling direction (RD) and the plate material width direction (TD) is small.

The magnesium alloy sheet according to an embodiment of the present invention has an average particle diameter

(Intermetallic compound) particles having an Mg-Ce-based secondary phase (intermetallic compound) of 0.5 pm to 20 / im, preferably Mg-Ce-based secondary phase (intermetallic compound) particles of 0. 5 to 5.

The magnesium alloy sheet according to an embodiment of the present invention may include Mn-based secondary phase particles having an average particle diameter of 1 m to 1 dish,

/ m. < / RTI >

Specifically, the magnesium alloy sheet material may include Mg-Ce, Mn, or a combination thereof. More specifically, the Mg-Ce system secondary phase may be a secondary phase containing Mg-Ce- (Zn) particles. On the other hand, the Mn-based secondary phase may be a secondary phase containing Mn- (Si) - (Fe) particles.

In addition, Mg-Ce-based second phase particles may be included from 1 to 30 per ^second area 100皿of the magnesium alloy plate.

In addition, at least one Mn-based secondary phase particle per 100 ² of the magnesium alloy sheet material may be included.

By including the Mg-Ce-based and Mn-based secondary phase particles in the size and number of the above-mentioned ranges, the moldability and corrosion resistance of the magnet alloy sheet material can be further improved. In order to obtain the Mg-Ce-based and Mn-based secondary phase particles described above, it is necessary to precisely control the composition range of the additive element, the temperature and time conditions in the homogenization heat treatment, the temperature and the rolling rate in warm rolling.

The magnesium alloy sheet material includes crystal grains, and the average grain size of the crystal grains can be 2 to 15. [ The moldability and the strength are further improved in the above-mentioned range . In order to obtain the crystal grains of the above-mentioned sizes, it is necessary to precisely control the composition range of the additive element, the silver and the time of the homogenization heat treatment, the temperature at the time of warm rolling, and the rolling rate.

In addition, the limiting imposed height of the magnesium alloy sheet according to an embodiment of the present invention may be 7 mm or more. More specifically, it may be 7 to 11 mm.

Generally, the threshold limit height is used as an index for evaluating the formability of the material, which means that the moldability of the material is improved as the height of the limit dome increases.

The above limited range is a marginal dome height which is significantly higher than a generally known magnesium alloy plate due to an increase in the grain boundary orientation distribution in the magnesium alloy sheet material. Accordingly, the magnesium alloy sheet material

The maximum gathering intensity may be 1 to 4 based on the [0001] plane.

If it exceeds the above-mentioned range, the moldability of the magnesium alloy sheet material may be inferior.

In addition, the corrosion rate of the magnesium alloy sheet according to an embodiment of the present invention may be 2.0 mm / y or less. Specifically, it may be 1.5 mm / y or less. This may be a result of limiting the composition, the composition range and the relational expression of the magnesium alloy sheet described above. In addition, it can be a result of optimizing the homogenization heat treatment and rolling conditions after controlling the Fe content, especially the impurities.

The magneto-alloy plate material may have a critical bending radius value at room temperature of 4 R / t or less, preferably 3 R / t or less. Also,

The critical bending radius value at 200 degrees Celsius can be less than or equal to 1.5 R / t.

Further, for the critical bending radius value in the rolling direction RD, the difference in the critical bending radius value in the plate material width direction TD may be 0 to 0.5 or less. This means that the anisotropy of the magnesium alloy sheet material is excellent. As described above, the excellent anisotropy of the magnesium alloy sheet means that there is little difference in physical properties between the rolling direction and the sheet width direction.

This is because the content of the additive element, the homogenization heat treatment condition, the rolling condition Is an effect that can be obtained by controlling the size and number of intermetallic compounds and the ratio of the two segregations of center segregation by optimization.

Further, the thickness of the magnesium alloy sheet according to an embodiment of the present invention may be 0.1 to 5 mm. The magnesium plate according to one embodiment of the present invention may be selected according to the properties required in the thickness range. However, the present invention is not limited thereto.

A method of manufacturing a magnesium alloy sheet according to another embodiment of the present invention is a method of manufacturing a magnesium alloy sheet material, wherein zinc (Zn) is contained in an amount of 0 to 2.0% by weight, manganese (Mn) (S100) of preparing a cast material by casting a molten alloy containing at least 0 wt% and 0.5 wt% or less of residual magnesium (Mg) and other unavoidable impurities; subjecting the cast material to a homogenization heat treatment (S200) Warm rolling the heat-treated cast material to prepare a rolled plate material (S300), and finally heat-treating the rolled plate material (S400).

First, in step S100 of preparing the cast material, the molten metal may satisfy the following relational expression (1).

[Zn] > [Mn] + [Ce]

Here, [Zn], [Mn], and [Ce] refer to weight percent of each component.

In addition, the Fe content in the other brittle impurities contained in 100 wt% of the alloy molten metal as a whole may be 100 ppm or less. The A1 content may be 0.3% by weight or less. However, the kind of the impurity is not limited thereto, and may include other unavoidable impurities.

The reason for limiting the composition and the composition range of the above-

The reason for limiting the composition and composition range of the magnesium alloy sheet is the same

It is omitted.

Specifically, in the casting step (S100), the alloy melt can be cast by gravity casting, continuous casting, strip casting (thin plate casting), sand casting, vacuum casting, centrifugal casting, die casting or chisel molding. Therefore

But the present invention is not limited thereto, and any method capable of producing a cast material is possible. Thereafter, the steps (S200) to homogenization heat treatment to the cast material may be carried out 300 degrees (° C) to 500 in Figure ⁽⁰ C). Further, the cast material is homogenized The heat-treating step may be conducted for 1 to 30 hours.

More specifically, the step (S200) of homogenizing the cast material may include a first homogenization heat treatment step (S210) and a second homogenization heat treatment step (S220).

Specifically, the first homogenization heat treatment step (S210) is performed at a temperature of 300 ° C

It can be carried out at 400 ° C. Further, the first homogenization heat treatment can be performed for 0.5 to 10 hours.

Also, the second homogenization heat treatment step (S220) can be performed at 400 ° C ( ⁰ C) to 500 ° C ( ⁰ ° C). In addition, secondary homogenization heat treatment can be performed for 0.5 to 20 hours.

More specifically, the low melting point phase can be subjected to solution treatment by performing the first heat treatment step (S210) as described above. In addition, by performing the secondary heat treatment step (S220) as described above, the homogenization heat treatment can smoothly proceed. Therefore, by dividing the homogenization heat treatment step (S200) into two steps as described above, surface oxidation due to local melting on the low melting point can be prevented.

That is, microstructure unevenness due to the superheating treatment can be prevented by homogenizing the casting material according to the temperature and time range, and the microstructure and segregation of the casting material can be sufficiently homogenized.

Then, the steps of: preparing a plate material by rolling, warm rolling the homogenization heat treated cast material (S300) may be carried out 150 (° C) to 400 in Figure ⁽⁰ C).

When hot rolling is performed in a temperature range lower than 150 degrees Celsius, a large amount of surface scattering type cracks or edge cracks may occur. On the other hand, when hot rolling at a temperature higher than 400 degrees Celsius (° C), the orange peel defect on the surface of the magnet alloy can be caused by the high temperature. In addition, equipment problems such as the necessity of changing the components of the equipment to heat-resistant materials for rolling at high temperatures may occur. As a result, problems such as an increase in process cost and a decrease in productivity are caused, and it is difficult to mass-produce magneto-alloy plates.

Further, in the step (S300), the cast material subjected to the homogenization heat treatment is subjected to heat treatment,

And can be warm-rolled at least once or twice at a reduction ratio of more than 0 and less than 40%. The homogenized heat-treated cast material can be warm-rolled using a warm rolling mill. When the cast material is warm-rolled at least two times, intermediate annealing may be performed at least once between the warm rolling. The intermediate annealing may be performed 300 degrees ⁽⁰ C) to about 500 in FIG. (° C). The intermediate annealing can be performed for 5 hours or less (excluding 0 hours). If the temperature and the time range are not satisfied, the stress of the hardened tissue is not sufficiently solved by the cumulative rolling reduction, and the annealing process may not be performed properly. Further, the abnormal crystal grains can grow due to excessive annealing.

Further, the intermediate annealing can be performed at a cumulative reduction of 40% or more of the rolled plate material. More specifically, in the case of performing intermediate annealing when the cumulative rolling reduction is 40% or more, generation and growth of new non-bottoms recrystallized grains can be facilitated in the structure formed during rolling. Thereby contributing to improvement of moldability of the magnesium plate material.

In the step of intermediate annealing the rolled sheet material, the intermediate annealing execution rate may be 20% or less. At this time, the intermediate annealing execution rate = (number of intermediate annealing / total number of rolling) X 100 can be obtained.

Thereafter, the step S400 of performing the final heat treatment of the rolled plate may be performed at a temperature of 250 ° C to 500 ° C. The step of final heat treatment of the rolled plate may be conducted for 5 hours or less (excluding 0 hours).

Specifically, when the final heat treatment temperature is less than 250 degrees Celsius ( ⁰ C), the formation and dispersion of the non-bottoms recrystallized grains by recrystallization are insufficient, so that the formability due to the range of the present invention may not be satisfied. On the other hand, if the final heat treatment temperature is higher than 500 ° C ( ⁰ ° C), surface oxidation may occur and it may not be possible to produce a perfect plate. Examples of the magnesium alloy sheet produced by the above-described method and

The comparative example will be described in detail below. The following examples are illustrative of the present invention only and are not intended to limit the scope of the present invention.

Manufacturing example

Examples and Comparative Examples were prepared with the components and compositions shown in Table 1 below. Concretely, a casting material was prepared by casting the alloy melt shown in Table 1 below. Then, the cast material was subjected to homogenization heat treatment for 1 to 30 hours at 300 ° C to 500 ° C ( ⁰ ° C). After the homogenization heat treatment process is completed,

And then warm-rolled at a reduction rate of 40% or less at a temperature of 150 ° C to 400 ° C. If the cumulative rolling reduction of the rolled plate is 40% or more, intermediate annealing may be applied at least once. The intermediate annealing process may be performed at a temperature between 300 [deg.] C and 500 [

(° C) for not more than 5 hours (excluding 0 hours). The sheet material produced through a warm rolling step is a final heat treatment was performed for 250 degrees ⁽⁰ C) to 500 degrees for 5 hours at (° C) (except for 0 hour) in order to improve formability.

[Table 1]

Evaluation example

As a result, the Erickson values, the V-bending test, and the salt precipitation test results of the above Examples and Comparative Examples were measured and are shown in Table 2 below. The Ericsson figure shows the goodness of the formability, the V-bending test shows the goodness of formability and anisotropy, and the corrosion property can be evaluated from the salt precipitation test.

At this time, evaluation methods of the respective properties are as follows.

[How to measure Ericsson numerical value]

A magnesium alloy sheet having a size of 50 to 60 mm respectively

And the friction between the plate and the spherical punch is reduced on the plane of the plate. A lubricant was used.

At this time, the temperature of the die and the spherical punch is set to room temperature.

Respectively.

More specifically, after inserting the magneto-alloy plate material between the upper die and the lower die, the outer peripheral portion of the plate material was fixed with a force of 10 kN, and then, using a spherical plate having a diameter of 20 mm, The plate was deformed. Thereafter, the punch was inserted until the plate material was broken, and then the deformation height of the plate material was measured at the time of breaking.

The deformation height of the plate measured in this manner is referred to as an Erickson value or

It is called the limit domed height (LDH).

[Measurement method of limit bending radius (V-bending)] [

In this specification, the V-bending test is performed as an index for measuring the degree of anisotropy of the formability, and the result is referred to as the limit bending radius (LBR). Specifically, the limit bending radius (LBR) value refers to the inner radius of curvature (R) of the plate after the bending test / the thickness (t) of the plate.

(RD) specimen was prepared so that the rolling direction was transverse, and the specimen in the width direction of the sheet material (TD) was transverse to the width direction of the sheet material. Respectively.

The prepared specimens were placed on a bending die having a length of 160 mm and a length of 80 mm, and the plate was placed at a rate of 20 mm / s at a speed of 20 mm / s using a bending punch having a lateral X-vertical size of 30 X 70 mm and an outer radius of curvature of 0 to 8R ^° was bending. At this time, the R value of the bending punch was varied while checking the presence or absence of a crack on the bending surface, and the crack was measured until no crack occurred. When the thickness of the specimen at that time is divided by the R value at which no crack occurs, the value of the limit bending radius (LBR), which is an index of bending anisotropy, can be obtained.

In case of normal temperature, all of the die, punch and plate were used without heating, and they were heated to 200 ° C at 200 ° C. The die and the preform were preheated to 200 ° C in advance, and the plate was tested immediately after heating to 200 ° C.

[Method of Measuring Corrosion Rate] The above-mentioned magnesium alloy sheet material was cut into a length of 95 mm and a width of 70 mm, and then the surface was polished using a lOOOgr it abrasive paper. Thus, a specimen having surface foreign substances and defects removed was prepared.

Subsequently, the plate materials according to Examples and Comparative Examples were immersed in 1 liter of sodium chloride (NaCl) solution at room temperature for 3.5 hours, and then immersed in the following solution for 1 minute in order to remove oxides formed on the surface. More specifically, the oxide-coated plate was immersed in a solution containing 100 g of anhydrous chromic acid and 10 g of silver chromate in 1 liter of distilled water at 90 ° C to remove the surface oxide.

Then, the corrosion rate was calculated through the weight of the plate before oxide formation and the weight of plate after oxide removal. More specifically, the corrosion rate was determined by dividing the weight loss of the plate after oxide removal by the area of the specimen, Respectively.

Corrosion rate = (initial weight of specimen - weight after removal of oxide) I (specimen area X density X salt precipitation time)

[Table 2]

As shown in Table 2, Examples 1 to 3 show that the Erickson value is 7 mm or more. More specifically, it can be seen that it is 8 mm or more. Also, the bend radius limit value at room temperature of 4 or less, limits the bending radius at 200 ^o C It is confirmed that the value is 1.5 or less. Further, it is confirmed that the anisotropy is excellent because the difference between the rolling direction (RD) and the plate bending radius (TD) is 0.5 or less, and the excellent corrosion resistance is also confirmed compared with Comparative Example 5 (AZ31) which is a commercial magnesium . Therefore, it was confirmed that the examples according to the present invention are excellent in both high corrosion resistance, room temperature moldability and anisotropy.

In addition, the composition of Mn in Comparative Example 2 was different from that of Example 1. As a result, in Comparative Example 2 including manganese, compared with Example 1, moldability

I was able to confirm the heat. In Comparative Example 2, unlike Example 1,

(1) was not satisfied. As a result, the rolling property was deteriorated and the moldability was improved.

In particular, in Comparative Example 3, when manganese was excessively added without addition of zinc, the physical properties could not be evaluated due to cracks.

Hereinafter, examples and comparative examples will be described with reference to FIGS. 1 to 3. FIG. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a photograph of a microstructure of the microstructure after (a) and (b) after homogenization heat treatment in Example 2 and Comparative Example 4 under an optical microscope.

Specifically, FIG. 1 shows changes in microstructure with and without addition of Mn when the contents of Zn and Ce are the same. Specifically, as shown in FIG. 1, it can be confirmed that the microstructure of Example 2 is finer than that of Comparative Example 4 in (a) after homogenization heat treatment and (b) after final annealing.

Specifically, the microstructure after the final annealing of Example 2 was about 2 to < RTI ID = 0.0 >

.

FIG. 2 is a photograph of the composition analysis of each intermetallic compound analyzed by a scanning electron microscope (SEM) and a backscattered electron (BSE) image using SEM-EDS.

As shown in the SEM-EDS photograph of FIG. 2, it can be confirmed that the intermetallic compounds such as 1 to 3 are abundant in the second embodiment.

Specifically, the intermetallic compound (1, 2) is an Mg- (Zn) -Ce intermetallic compound formed by the addition of Ce. On the other hand, the intermetallic compound (3) is an Mn- (Si) - (Fe) intermetallic compound formed by the addition of Mn.

As described above, in the case of intermetallic compounds 1 and 2, magnesium There is a characteristic that the chemical potential difference with the base is not large. Accordingly, the intermetallic compounds 1 and 2 can reduce the galvanic corrosion due to the potential difference with the magnesium base. On the other hand, Mg-Al intermetallic compounds generated from commercial magnesite alloys not containing Ce may cause galvanic corrosion due to the potential difference with the magnesium base.

In addition, when the intermetallic compound 3 is used, impurities such as Si and Fe are refined. Accordingly, the content of the impurity Fe may be lower than that of the magnesium alloy not containing Mn. Accordingly, the magnesium alloy sheet according to the embodiment of the present invention has a Fe content of less than lOOppm, and the corrosion rate may be less than 2mm / y.

On the other hand, in the case of Comparative Example 4 in which the content of Mn is not included and the content of Fe (non-ferrous metal) is not less than lOOppm, the formability is similar to that of Examples but the corrosion resistance (corrosion rate) .

Accordingly, by including the intermetallic compounds such as the intermetallic compounds 1 to 3, the magneto-alloy plate according to the embodiment of the present invention can have an improved corrosion resistance and a corrosion rate of 2 mm / y or less.

3 is a graph showing the results of a salt water immersion test (Sal t

Immersion test) and the corrosion product is removed.

Specifically, after each corrosion, each plate was heated to 90 degrees (° C)

This is a surface image obtained by immersing in an aqueous solution of xylene for 1 minute to remove corrosion products. In Examples 1 to 3, it is possible to identify a surface on which metal luster is maintained without causing almost no corrosion. On the other hand, in the case of Comparative Example 4 in which Mn was not included, many corrosion occurred, and in Comparative Example 5 (AZ31), which is a commercial magnesium alloy, corrosion was caused by severe galvanic corrosion.

Fig. 4 shows a comparison of the {0001} XRD pole figure of the embodiment and the comparative example.

Specifically, the contour line according to the pole figuration is a stereo projection of the direction of the arbitrarily fixed crystal coordinate system in the specimen coordinate system. More specifically, the poles for the [0001] planes of the crystal grains of various orientations are displayed in the reference coordinate system, and the density contour lines are plotted according to the pole density distribution It is possible to show pole figure. At this time, the poles are fixed in a specific lattice direction by the Bragg angle, and a plurality of poles can be displayed for a single crystal. Therefore, the smaller the density distribution value of the contour line represented by the poling method is, the more the crystal grains of various orientations are distributed. The larger the density distribution value is

[0001] // It can be interpreted that a large number of crystal grains are oriented in the C axis direction.

The maximum aggregate strength of the [0001] plane is the result of analyzing the crystal orientation of the magnesium alloy sheet by the above-described XRD analyzer.

It can be confirmed that the maximum density distribution value (aggregate intensity) of the [0001] plane in Examples 1 to 3 is a very small value of 4 or less. In addition, the {0001} bottom surface organization is distributed much in RD and TD directions,

It can be confirmed that it is distributed. In other words, it can be deduced that the maximum aggregate intensity value is small and the contour lines are widely spread and the crystal grains of various orientations are distributed in the embodiment.

On the other hand, in the case of the comparative example 5, it can be seen that the {0001} bottom surface texture is concentrated and the peak intensities are very high.

Further, in the case of Comparative Example 1, it can be seen that the {0001} underside texture is not uniformly distributed in the RD and TD directions. In other words, it can be seen that the comparative example contains much crystal grains of // C axis orientation compared to the embodiment, since the maximum set intensity value is large and the contour lines are dense. From this, it can be seen that the embodiment is more excellent in moldability than the comparative example.

5 is a photograph of the {0001} XRD pole figure and EBSD of Example 2 and Comparative Example 5. Fig.

The crystal orientation of grains can be measured not only by the pole figuration described above, but also by the EBSD image. More specifically, the EBSD can introduce electrons into a specimen through an electron beam and measure the crystal orientation of the crystal grains using inelastic scattering diffraction at the back of the specimen.

Specifically, it can be seen that the maximum set intensity value of Example 2 is very low as 2.79, while the maximum set intensity value of Comparative Example 5 is as high as 12.11. From this, it can be deduced that in Example 1, a large number of non-base texture tissues deviated from the orientation in the bottom-side texture structure are distributed As shown in the EBSD image, since the crystal grains of various colors are distributed in the second embodiment compared to the second comparative example, it can be seen that the texture of the underside is distributed widely. Specifically, in Comparative Example 5, it is visually confirmed that crystal grains (red) corresponding to the crystal orientation of the [C] -axis orientation are larger than those of Example 2.

FIG. 6 is a graph showing the results of V-bending test at room temperature (a) and 200 ^° C (b) of Example 2, showing the microstructure of the RD (Rolling Diode) It is a photograph observed with an optical microscope.

As shown in Fig. 6, it can be confirmed that no bimolecular segregation exists in the magnesium alloy sheet material in both the RD direction and the TD direction at room temperature (a) and 200 ° C (b) of Example 2. Specifically, the thickness ratio of the center segregation in Example 2 may be 10% or less.

If the percentage of thickness of the center segregation exceeds 10%, the anisotropy of the magnesium alloy sheet material may be deviated. Thus, in Example 2, the thickness ratio of the center segregation is 10% or less, so that anisotropy in the RD and TD directions can be excellent.

According to the above description, when controlling the contents of Zn, Mn and Ce elements, fine Mg-Ce and Mn secondary phases can be formed according to the embodiment of the present invention. Accordingly, the aggregate intensities (peak intensities) of [0001] bases are 1 to 4, and thus microstructures having a large number of non-subsurface texture can be obtained. Also, it is possible to manufacture a magnesium alloy plate of high moldability and high corrosion resistance having a high room temperature Erickson value of 7 to 11 mm and a low corrosion rate of 2.0 mm / y or less.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It is obvious to those who have. Accordingly, such modifications and variations are intended to be included within the scope of the present invention,

It should be understood that the modified embodiments are within the scope of the claims of the present invention.

Claims

Claims:

[Claim 1]

For a total of 100% by weight,

Zinc (Zn) is more than 0 to 2.0 wt%

Manganese (Mn) is more than 0 to 1.0% by weight,

Cerium (Ce) is more than 0 and 0.5 wt%

Magnesium alloy plate containing remainder magnets (Mg) and other unavoidable impurities

[Claim 2]

The method of claim 1,

Wherein the magnesium alloy sheet material satisfies the following relational expression (1).

[Zn] > [Mn] + [Ce]

(Wherein, [Zn], [Mn], and [Ce] mean the weight of each component).

[Claim 3]

In paragraph 12,

And the other unavoidable impurities include Al: 0.3 wt% or less and Fe: 100ppm or less.

Claim 4

In paragraph 3,

Wherein the thickness ratio of the core segregation sheet to the core segregation sheet is 10% or less.

[Claim 5]

In addition,

The average particle size of the Mg-Ce system secondary phase is 0.5 // m to 20,

Wherein the magnesium alloy sheet material comprises 1 to 30 magnesium alloy sheets per 100 ^{2 of} the magnesium alloy sheet material.

[Claim 6]

The method of claim 5,

The average particle size of the Mn-based secondary phase is 1 to 15 / dish, Wherein at least one magnesium alloy sheet material is contained per 100 ² of the magnesium alloy sheet material.

7.

In Paragraph 16,

Wherein the maximum aggregate strength of the base of the magnesium alloy sheet material is not less than 1 and not more than 4.

[8]

8. The method of claim 7,

Wherein the magnesium alloy sheet has a normal-temperature Erickson value of 7 to 11 mm.

[Claim 9]

9. The method of claim 8,

The manganese alloy sheet material is a magnesium alloy sheet having a corrosion rate of 2.0 mm / y or less.

Claim 10

The method of claim 9,

Wherein the magnesium alloy sheet material has a critical bending radius value at room temperature of 4 R / t or less.

[Claim 11]

11. The method of claim 10,

The magnesium alloy sheet has a limiting bending radius value at 200 ^o C of 1.5

R / t or less.

Claim 12

12. The method of claim 11,

Wherein the magnesium alloy sheet material has a difference between a rolling direction (RD) and a limiting bending radius value of the plate material width direction (TD) of 0.5 R / t or less.

Claim 13

The method of claim 1,

The cerium may be either a cerium element alone or a cerium-

Magnesium alloy sheet contained in mi-metal (mi schmetal) form.

14.

The method of claim 13,

Wherein the micro metal further comprises another rare earth element.

15.

(Mn) is not less than 0 and not more than 1.0 wt%, cerium (Ce) is not less than 0 and not more than 0.5 wt%, and the balance of magnesium (Mg) and Casting an alloy melt containing other unavoidable impurities to prepare a cast material;

Subjecting the cast material to homogenization heat treatment;

Hot rolling the homogenized heat treated cast material to prepare a rolled sheet material; And

And finally heat-treating the rolled plate material.

Claim 16

16. The method of claim 15,

Wherein the alloy melt satisfies the following relational expression (1): " (1) "

[Zn] > [Mn] + [Ce]

(Wherein, [Zn], [Mn], and [Ce] mean the weight of each component).

[Claim 17]

17. The method of claim 16,

Wherein the other unavoidable impurities include Al: 0.3 wt% or less and Fe: lOOppm or less.

Claim 18

16. The method of claim 15,

A method of manufacturing a magnet alloy sheet material which is carried out at 500 ° C (° C).

[Claim 19]

The method of claim 18, The step of subjecting the cast material to a homogenizing heat treatment may be performed for 1 to 30 hours

A method for manufacturing a magneto-metallic alloy plate,

[20]

16. The method of claim 15,

Wherein the step of subjecting the cast material to a homogenizing heat treatment includes:

A first homogenization heat treatment step; And

And a second homogenization heat treatment step.

21.

20. The method of claim 20,

Wherein the first homogenization heat treatment step is performed at a temperature of from 300 [deg.] C to 400 [

A method for producing a magnesium alloy sheet material,

[22]

22. The method of claim 21,

Wherein the primary homogenization heat treatment step is performed for 0.5 to 10 hours.

[Claim 23]

20. The method of claim 20,

The second homogenization step is a heat treatment at 400 degrees ⁽⁰ C) to about 500 degrees (° C)

A method for manufacturing a magneto-metallic alloy plate,

24.

24. The method of claim 23,

Wherein the secondary homogenization heat treatment step is performed for 0.5 to 20 hours.

25.

16. The method of claim 15,

The method of the homogenized heat treatment to the cast material comprising: preparing a plate material by rolling the rolling is warm rolling the magnesium is carried out to 150 degrees ⁽⁰ C) to 400 in Figure (° C) alloy plate.

26. The method of claim 26,

26. The method of claim 25, Wherein the step of hot-rolling the homogenized heat-treated cast material to prepare a rolled sheet material is performed at a reduction ratio of 0 to 40% or less per rolling.

[27]

16. The method of claim 15,

Wherein the step of rolling the homogenized heat-treated cast material to prepare a rolled plate material further comprises intermediate-annealing the rolled plate material.

28. The method of claim 28,

28. The method of claim 27,

Wherein the intermediate annealing is performed at least once during hot rolling the rolled plate material twice or more, and the cumulative rolling reduction ratio of the rolled plate material is 40% or more.

Claim 29

29. The method of claim 28,

In the step of intermediate annealing the rolled sheet material,

And the intermediate annealing execution rate is 20% or less.

30.

30. The method of claim 29,

Wherein the intermediate annealing is carried out at a temperature of 300 ° C (500 ° C) to 500 ° C (° C).

31. The method of claim 31,

32. The method of claim 30,

Wherein the intermediate annealing is performed for 5 hours or less (excluding 0 hours).

32. The method of claim 32,

16. The method of claim 15,

Wherein the step of subjecting the rolled plate to a final heat treatment is performed at a temperature ranging from 250 ° C to 500 ° C.

33. The method of claim 33, 32. The method of claim 32,

Wherein the final heat treatment of the rolled plate is performed for 5 hours or less (excluding 0 hours).