JPS60204825A - Manufacture of steel belt - Google Patents

Abstract

PURPOSE:To obtain a high strength steel belt capable of compacting a conveyor and extending the field of utilization by forming a thin-walled cylinder of maraging steel by cold flow forming, aging the cylinder, and nitriding it as required. CONSTITUTION:A rough pipe of maraging steel is subjected to soln. heat treatment at the austenite transformation point or above and cold flow forming in a state in which the tube has low strength.The resulting cylinder is subjected to intermediate soln. heat treatment and final cold flow forming to form a thin- walled cylinder. This cylinder is cut to the shape of a steel belt, and it is aged to increase the strength by precipitating a fine intermetallic compound. Nitriding may be carried out furthermore to improve the fatigue strength. When the resulting belt is used, a belt conveyor and a conveyor pulley can be reduced in weight.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is directed to a high-strength steel that can be used to make belt transmission devices, conveyor pulleys, etc. more compact and lightweight, and to enable expansion into the conventional gear transmission field. This invention relates to a belt manufacturing method.

[Background technology]

Steel belts are widely used in various equipment operating devices and conveyors. Figure 1 shows the relationship between the pulley diameter and the stress generated in the belt.

Both the stress generated for torque transmission and the stress generated by the pulley or belt wheel act on the belt, but as is clear from Figure 1, the stress generated by the pulley depends on the pulley diameter; It can be seen that the smaller the diameter of the

Currently, the strongest steel belt in practical use is one with a tensile strength of 13 oki/-, and when this is used, the diameter of the pulley is 800 to 1000 mφ. However, it was difficult to make the steel belt more compact and lightweight.

In addition, since the above-mentioned stress acts repeatedly on steel belts, it is required to have high fatigue strength in addition to tensile strength, but conventional steel belts are insufficient in this respect as well. It was not possible to reduce the weight.

[Object of the present invention]

The present invention eliminates these drawbacks and manufactures a high-strength steel belt that can make belt transmission devices, conveyor pulleys, etc. more compact and lightweight, and also expand its use in the field of conventional gear transmission. The purpose is to provide a method.

[Configuration of the present invention]

As a means to achieve the above object, the present invention uses maraging steel, which has excellent strength, toughness, and cold workability and has been conventionally used in the fields of nuclear power and aerospace, as a steel belt material. In addition, cold 70-form processing and aging treatment are combined, and nitriding treatment is further combined after the aging treatment.

That is, the present invention consists of two inventions. The first invention is a production of a steel belt characterized in that maraging steel is formed into a thin cylinder by cold 70-form processing and subjected to aging treatment. As for the method, the second invention is a method for producing a steel belt, characterized in that a nitriding treatment is further performed after the aging treatment of the first invention.

Hereinafter, when it is not necessary to distinguish the present invention as two inventions,
That is, when explaining the common features of two inventions, the present invention is simply referred to as the present invention, and when it is necessary to distinguish the present invention as two inventions, the above-mentioned first invention of the present invention is referred to as the first invention,
The second invention of the present invention is referred to as the second invention.

Specifically, the first invention involves cold flow forming a maraging steel pipe in a low-strength state that has been solution-treated at a temperature above the austenite transformation point,
Thereafter, an intermediate solution treatment and a final cold flow forming process are performed to produce a thin-walled zero cylinder, which is then sliced into rounds to create the shape of a steel belt. After this, an aging treatment is performed in a temperature range where fine intermetallic compounds precipitate and high strength can be achieved.

Specifically, following the aging treatment of the first invention, the second invention further provides nitriding treatment in a temperature range that provides a nitriding depth of several tens of μm and high surface hardness, in order to further improve fatigue strength. It is characterized by carrying out the following.

The belt manufactured in this manner has a tensile strength of approximately 250 kg/- in the first invention, and a fatigue strength of 120 kg/- in addition to this tensile strength in the second invention. ], by using the belts obtained by these two inventions, the diameter of the pulley can be reduced to about 100-φ, making it possible to achieve compactness and weight reduction.

As described above, the first invention is industrially valuable as a method for manufacturing a steel belt with high strength, and the second invention is a method for manufacturing a steel belt with high strength and high fatigue strength. It can be said that there is.

In the present invention, any maraging steel can be used as the material for the steel belt, but maraging steel having the following composition range is particularly preferred.

Weight composition ratio: 12 to 26 nickel, 7 to 15 cobalt
3-10% molybdenum, titanium [1,1-2.0%], aluminum α03-α30, balance iron and carbon,
Maraging steel containing unavoidable impurities such as phosphorus and sulfur.The reason why maraging steel with this composition range is good is as follows. N
The reason for setting 1 to 12 to 26% is to keep the matrix as martensite and improve toughness.
The reason why CO was set at 7 to 15% was to increase the strength by precipitation of intermetallic compounds, and the reason why the MO was set at 3 to 10% was because if it was more than this, toughness would be impaired.
As in the case of 00 above, this is to increase the strength by precipitation of an intermetallic compound (Fθ-Mo type), and if the amount exceeds this amount, undissolved coarse precipitates will appear and impair toughness. Also, the reason why Ti is set to α1 to 2.0 is to increase the strength of the intermetallic compound (N1-Ti type), and too much will impair the toughness. The reason why the thickness is set to α03 to α30% is to create an intermetallic compound (Ni-At type) to increase the strength.

Further, in the present invention, as the material for the steel belt, it is also suitable to use maraging steel having the following composition range.

Weight composition ratio: nickel 3-5, cobalt 11-14
%, molybdenum 4.5-5.5%, titanium α1-zO%
, aluminum α03 to α3, chromium 11 to 13,
Maraging steel containing the balance iron and unavoidable impurities such as carbon, phosphorus, and sulfur. The reason why this composition range is preferable is as follows. N
The reason why 1 is set at 5 to 5% is to have the effect of suppressing the formation of δ ferrite, and to improve the toughness at the same time as martensitic (K) matrix, and the reason why CO is set at 11 to 14% is to have the effect of suppressing the formation of δ ferrite. The reason for setting Mo4.5 to 5% is to increase the strength by precipitation of intermetallic compounds (Fe-M).

This is to increase the strength through the precipitation of silane (based on nitride), and if the amount exceeds this amount, undissolved coarse precipitates will appear and impair toughness. The reason for setting T1 to 11 to 2.0 is to increase the strength of the intermetallic compound (Ni-Ti type), and too much will impair toughness. The reason why At is set to α03 to α30 is to increase the strength of intermetallic compounds (Ni-At type).Also, or is set to 11 to α30.
The reason why it is set at 13% is that it dissolves in the matrix and improves corrosion resistance. If it is too small, the corrosion resistance will be insufficient, whereas if it is too large, δ ferrite will precipitate.

In the present invention, maraging steel having the above two component ranges is suitable as a material for the steel belt, but specific examples include 12Ni, 18Ni, 2ONi
and 81Ji-6 (!r).In the present invention, it is preferable to use raw tubes made of maraging steel, which is the material of these steel belts, as raw materials. The reason is
This is because it is suitable for seamless steel belts, and it is also advantageous for improving the material quality of steel belts, such as improving strength.

In addition, in the present invention, a thin-walled cylinder is formed by cold flow 7-ohm processing, but this is done by cold-processing a thick-walled cylinder using combination K on a mandrel 0- to form a thin-walled cylinder. The method for obtaining this will be explained in detail with reference to FIG. FIG. 2 shows an example of a device suitable for the cold flow form of the present invention. In the figure, 1 is a rotatable mandrel, 2 is a roll for ironing, 3 is a backup roll, and 4 is an axial center positioning center. , 5 indicates the original shape (the shape of the workpiece before processing). 6 indicates the cylinder obtained by flow 7 ohm processing, O indicates the original thickness before processing, the thicknesses obtained by the first to fourth processing of Mu to DFi, respectively, and F indicates the flange.

A thick-walled cylindrical workpiece having a 50 element shape is attached to the mandrel 1, fixed as shown in the figure by the axial center positioning core 4, and the roll 2 and backup roll 3 are pressed against the workpiece while rotating the mandrel 1. , and move the mandrel and workpiece in the axial direction to perform ironing. By the first operation described above, the cylinder in the original shape of 5 is thinly extended into a cylinder with a wall thickness of A. By repeating the above operations in steps 2, 5, etc., finally (in this case, the fourth time), a cylinder D with a thin wall thickness and an elongated length can be obtained. This example shows the case where the flange F is left at the end, but
In some cases, it may be pushed out all the way to leave the flange intact.

This cold flow 7 ohm processing method is suitable for manufacturing seamless steel belts and is an advantageous method for improving the material quality of steel belts, such as increasing thickness and improving strength.

In the present invention, maraging steel is formed into a thin cylinder by cold 70-form processing.
Specifically, this raw material pipe made of maraging steel is used as a raw material, and this raw material pipe is subjected to solution treatment in a temperature range above the austenite transformation point, and is cold-hardened for 70 minutes in a low-strength state.
- Preferably, thin-walled cylinders are produced by forming, followed by intermediate solution treatment and final cold flow forming. The reason for performing the above-mentioned solution treatment in the initial state of the raw tube is to uniformly disperse the alloying elements in the austenite.The reason for performing the above-mentioned intermediate solution treatment is This is to improve grain size, increase strength, and increase toughness by combining with flow 7 ohm, which is a cold working process. The appropriate temperature range and time for these solution treatments are 780-840°C and 3.
The duration is 0 minutes to 2 hours.

As a specific example of the present invention, as described above, by combining solution treatment and flow forming processing in two stages, grain refinement is further promoted, which is effective in increasing strength and toughness. However, this solution treatment may be performed in one stage, and since this solution treatment is performed to uniformly disperse the alloying elements and prepare the structure, in the present invention, in the case of one stage, the structure is adjusted from the beginning. This solution treatment is not necessary if a well-formed material is used.

In addition, the range of the wall thickness of the thin cylinder in the present invention is α2~
α8 tm is a preferred range. This is a preferable range from the viewpoint of rigidity as a steel belt, advantages in manufacturing a thin-walled cylinder, and stress and weight. That is, when this thickness is α8 tss or less, when performing flow 7 ohm processing, it is possible to uniformly extend the entire outside and inside of the raw pipe in the thickness direction.

Therefore, the properties of the material such as strength can be made uniform throughout. If the thickness is equal to or greater than α8 tfi, only the surface will be elongated when flowform processing is performed, and the properties will be different between the outside and the inside. Furthermore, as is clear from FIG. 1, the thinner the boot, the less stress is generated on the seatbelt by the boot, and the weight is also smaller. On the other hand, α2, which is the lower limit of the thickness of this thin cylinder
- cannot be lower than this when performing flow form processing, and must be higher than this.

In addition, the reason why the aging treatment is performed in the present invention is to increase the strength by uniformly precipitating fine intermetallic compounds containing Ni, MO, etc. in the matrix of the grain side. Precipitation of intermetallic compounds is temperature dependent. As a result of the test, it was found that a temperature between 400°C and 550°C was suitable, although it differed depending on the material. If the temperature of this aging treatment is lower than 400℃, it will take time for precipitation,
If the sweetness is low, precipitation itself will not occur. On the other hand, if this temperature is higher than 550°C, the intermetallic compounds will become coarse and the strength will not increase much. In addition, if it is too high, austenite will precipitate and the strength will be lowered.

Note that the appropriate aging treatment time is normally 3 to 5 hours.

In the second invention, the reason for performing the nitriding treatment is to improve the fatigue strength, and this treatment is performed by several tens of microns.
It is preferable to carry out the nitriding in a temperature range where a nitriding depth of m and high surface hardness can be obtained. Normal nitriding treatment is 500℃~550℃
It is carried out by heat treatment for several hours to hundreds of hours in an ammonia gas stream.

Hereinafter, specific examples of the first invention and the second invention will be given and both inventions will be explained in detail.

[Specific Example of the First Invention] The steel used in the test was a so-called 18Ni type maraging steel, sb, 1a, 30% Ni, 12.05% C! o, 432
The material had a composition of 1.46% Mo, 1.46% Ti, α08% At, and the remainder Fe. This maraging steel raw tube was processed and heat treated as described below to obtain a steel belt. The cold working rate is expressed as to-tt/lo (where 1 (, indicates the thickness of the original member, and tl indicates the thickness of the member after processing).

That is, a raw pipe with a wall thickness of 20 vm and an inner diameter of 500 mm was subjected to solution treatment at a temperature of 8°C above the austenite transformation point (700°C).
Heat to 20°C, hold at that temperature for 1 hour, solution treatment, and then cool (by air cooling) to form a wall thickness of 20-1 and an inner diameter of 500 m.
After making it into a low-return martensite state with a tensile strength of 112 kg/, and high elongation, cold flow forming processing (first stage) with high processing efficiency and high processing accuracy was performed.The obtained member was Wall thickness t5■, inner diameter 500■ (cold working rate 9
2.5%) and a tensile strength of 158 kg7wm”.

Solution treatment of the above parts again (temperature 820℃ for 1 hour)
After the processed structure caused by the first cold flow 7-ohm processing was erased, it was air-cooled and a second cold-flow 70-form processing was performed. The purpose of this intermediate solution treatment is to prevent the processing rate of the cold flow form from becoming too large and cause cracks, etc., and to improve the mechanical properties, especially 1 elongation, after the aging treatment in the next process. went. In addition, the second flow form processing rate was set at 80 inches in consideration of prevention of cracking due to the flow of 7 ohms and strength and elongation after final processing.

A thin-walled cylinder with a thickness of 9/cm (L3 mm, inner diameter of 500 mm, tensile strength of 114 and 9/cm3) made by secondary flow 7 ohm processing was cut into rounds to the belt width (20 mm) before aging treatment. Thickness (
L3■, inner diameter 500m, length 20mm, tensile strength 126
'qlZ-, which was then aged at 520°C for 5 hours and air cooled to produce a seamless steel belt with a wall thickness of α3m, an inner diameter of 500m, and a length of 20m.

The tensile strength F of the steel belt manufactured by this method
9/■2 for i2s4, (L2chi strength is 246kP/,"
, fatigue strength tri 90 kg/m"te% ft-
0 [Specific Example of the Second Invention] The seamless steel belt produced in the above-described specific example of the first invention was further subjected to the nitriding treatment described below to produce a steel belt. That is, after performing the aging treatment at 520°C for 5 hours as described in the specific example of the first invention, the nitriding treatment was further performed at 500°C for 15 minutes, followed by air cooling. − A seamless steel belt was manufactured. The specific conditions for this nitriding treatment are as follows.

The nitriding treatment was carried out by holding the sample in an ammonia stream maintained at a temperature of 500° C. for 15 minutes.

Although it is very difficult for steel to absorb molecular nitrogen, when it comes into contact with NH3 gas, it easily combines with a large amount of nitrogen. That is, NHs Fi decomposes as NH3→M+3H at high temperatures, but this decomposition proceeds particularly rapidly on the steel surface.
Nascent N reacts with steel to form nitrides.

Through such treatment, the surface hardness becomes 10 on the Vickers scale.
A material with high fatigue strength reaching 00 to 12001C can be obtained.

Normal nitriding treatment is carried out by heat treatment for several hours to hundreds of hours in an ammonia stream of 500 to 550 tons. 5o to obtain hardness and appropriate hardening depth.

A nitriding treatment was performed for 15 minutes using cr.

The fatigue strength of the steel belt manufactured by this method is approximately 120 ky/■2, and the tensile strength is 257 kg/
■", α2chi proof stress 248 J/wm" Terror.

The hardness distribution of the steel belt manufactured in the specific example of the second invention, that is, the hardness distribution after the nitriding treatment, is
As shown in the figure. Further, FIG. 4 shows the fatigue test results of the steel belts manufactured in the specific example of the first invention and the specific example of the second invention, that is, the fatigue test results with and without nitriding treatment. As is clear from FIG. 4, the fatigue strength was improved by about 5okII7- by the nitriding treatment.

[Effects of the present invention]

As described in detail above, the first invention is made by subjecting maraging steel to cold 70-7 ohm processing and aging treatment, so that a high-strength steel belt can be obtained. Since the second invention is further subjected to nitriding treatment, there is an effect that a steel belt with high strength and high fatigue strength can be obtained, and both inventions can make belt transmission devices, conveyor pulleys, etc. compact and lightweight. This makes it possible to expand its use in the field of conventional gear transmission.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between the pulley diameter and the stress generated by the pulley, Figure 2 is an example of the cold flow forming equipment used in the present invention, and Figure 5 is after nitriding. FIG. 4, which is a hardness distribution diagram of a cross section of a steel belt, shows the fatigue test results of a steel belt manufactured according to the present invention. Sub-agent 1) Clearance agent Ryo Hagiwara - Stress generated in the belt by the pulley '9/n Rin 2, 2, 3, 4, 3 Ij, NL number of complaints

Claims (2)

[Claims] (1) A method for producing a steel belt, which comprises forming a thin-walled cylinder by maraging/steel t-cold 70-form processing and subjecting it to aging treatment. (2) A method for manufacturing a steel belt, which comprises forming maraging steel into a thin cylinder by cold processing to 70-7 ohm, and subjecting it to aging treatment and nitriding treatment.