CN109913758B - Ferritic stainless steel plate with good high-temperature strength and forming performance and preparation method thereof - Google Patents

Abstract

The ferritic stainless steel plate with good high temperature strength and formability and the preparation method thereof of the invention belong to the technical field of stainless steel preparation. The ferritic stainless steel plate contains C≤0.01% and N≤0.006-0.01% in terms of mass percentage. , Si 0.4～0.6%, Cr 18～20%, Mo 1.8～2.1%, Nb 0.2～0.5%, Ti 0.1～0.2%, W 0.4～1.5%, Ce 0.04～0.1%, Mn 0.25～0.35%, S ≤0.005%, P≤0.01%, the balance is Fe. During preparation, after smelting, casting and forging in turn, hot rolling and cold rolling are carried out at the corresponding temperature in turn, and the reduction rate and the annealing temperature after two rollings are controlled, and the ferrite with good high temperature strength and formability is obtained by cooling. Body stainless steel plate. The present invention improves the high temperature strength of ferritic stainless steel by adding an appropriate amount of W, and provides an optimized rolling process, so that ferritic stainless steel sheets with good high temperature strength and formability can be produced, which are used for automobile exhaust manifold heat treatment. high temperature working environment of parts such as terminals.

Description

Ferritic stainless steel sheet with good high temperature strength and formability and preparation method thereof

Technical field:

The invention belongs to the technical field of stainless steel manufacturing, and in particular relates to a ferritic stainless steel plate with good high temperature strength and formability and a preparation method thereof.

Background technique:

Ferritic stainless steel has excellent oxidation resistance, corrosion resistance and good thermal fatigue resistance, and is widely used in automotive exhaust systems, electrical appliances, fuel cells and nuclear power and other fields.

With the stricter and stricter automobile exhaust emission standards and the continuous improvement of fuel efficiency, the temperature of automobile exhaust gas will continue to rise. The local working temperature of the exhaust manifold directly connected to the engine will reach 950 to 1050 ° C, or even as high as 1100 ° C; considering the complex structure of the exhaust manifold, it must have excellent forming performance. Therefore, ferritic stainless steels with excellent high temperature strength and formability are in great demand.

Invention content:

The object of the present invention is to overcome the deficiencies of the above-mentioned prior art, and provide a ferritic stainless steel plate with good high temperature strength and formability and a preparation method thereof. , cold rolling and cold rolling annealing treatment to make ferritic stainless steel sheet with good high temperature strength and formability.

To achieve the above object, the present invention adopts the following technical solutions:

A ferritic stainless steel plate with good high temperature strength and formability, including components and mass percentages of C≤0.01%, N 0.006-0.01%, Si 0.4-0.6%, Cr 18-20%, Mo 1.8- 2.1%, Nb 0.2～0.5%, Ti 0.1～0.2%, W 0.4～1.5%, Ce 0.04～0.1%, Mn 0.25～0.35%, S≤0.005%, P≤0.01%, the balance is Fe and unavoidable impurities.

The ferritic stainless steel sheet with good high temperature strength and formability has a tensile strength σ _s ≥ 18 MPa at 1100° C., a yield strength σ _0.2 at room temperature is 360-400 MPa, and a tensile strength σ _b at room temperature is 570- 611MPa, the elongation after fracture at room temperature δ≥28%, the average plastic strain ratio rm ≥1.4, the anisotropy _Δr≤0.1 , the average surface roughness after 15% deformation along the rolling direction _Ra≤1μm .

The preparation method of the ferritic stainless steel plate with good high temperature strength and formability includes the following steps:

(1) Smelting molten steel according to the set composition and casting it into steel ingots, the composition is calculated by mass percentage, including C≤0.01%, N0.006～0.01%, Si 0.4～0.6%, Cr 19～20%, Mo 1.9～2.1 %, Nb 0.2～0.5%, Ti 0.1～0.2%, W0.4～1.5%, REM0.04～0.1%, Mn 0.25～0.35%, S≤0.005%, P≤0.01%, the balance is Fe;

(2) Forging the steel ingot into a slab, the forging temperature is 1200-1250 ° C, and air-cooled to room temperature after the forging is completed;

(3) The air-cooled slab is heated to 1150-1250°C, and after 1-3 hours of heat preservation, 6-8 passes of hot rolling are carried out. The reduction ratio is 85-90%, and the hot rolling is completed and air-cooled to room temperature;

(4) annealing the air-cooled hot-rolled sheet at 1025-1075 ℃, the annealing time is 3-8 min, and then air-cooled to room temperature;

(5) Cold-rolling the hot-rolled annealed sheet at room temperature, with a total reduction ratio of 75-85%, annealing at 1025-1075°C after cold-rolling, annealing time is 1-3min, and air-cooled to room temperature after annealing, The prepared ferritic stainless steel plate with good high temperature strength and formability.

In the step (2), the thickness of the slab formed by forging is 40-60 mm.

In the step (3), the single-pass reduction ratio during hot rolling is 20-40%.

In the step (5), the single-pass reduction rate during cold rolling does not exceed 10%.

In the step (5), the prepared ferritic stainless steel plate with good high temperature strength and formability has a thickness of 1-2 mm.

The reason for the limitation of components in the present invention will be explained, and the content of each element in the steel is a mass percentage. Both C and N elements in ferritic stainless steel reduce the r-value, elongation and corrosion resistance of the finished sheet. In addition, there is a strong affinity between C, N and Cr, and it is easy to form chromium carbides and nitrides with Cr, causing the depletion of chromium and reducing the high temperature oxidation resistance and intergranular corrosion resistance of the material. These negative effects are more pronounced if the total content of C and N exceeds 0.03%. However, if the total content of C and N is less than 0.005%, it will promote the growth of columnar crystal solidification structure, which is not good for the ability of the finished board to resist surface wrinkling. It is also considered that the ductile destruction effect of C element on ferritic stainless steel is significantly greater than that of N element, and increasing the N content can improve the strength of the steel without reducing the toughness of the steel. Therefore, the C content should not be higher than 0.01%, and the N content should be controlled at 0.006-0.01%.

Si can deoxidize in steel and improve oxidation resistance. However, when the Si content exceeds 1%, the formability and plasticity of the finished sheet will be reduced. Therefore, the Si content is controlled at 0.4 to 0.6%.

Cr is the main element that determines the corrosion resistance of stainless steel, which can increase the potential of the substrate electrode, thereby significantly improving the corrosion resistance of steel. In addition, Cr is the main component of the oxide film, which helps to form a more stable oxide film and improves the oxidation resistance at high temperature. However, as the Cr content increases, the formability of the ferritic stainless steel decreases. Therefore, the Cr content is limited to 18 to 20%.

Mo can significantly increase the stability of the passive film on the steel surface and prevent it from being locally broken down in harsh aggressive environments. Mo also enhances resistance to localized corrosion such as pitting, crevice corrosion, especially in the presence of chloride ions in halogen salts or seawater. In addition, Mo can also provide solid solution strengthening and precipitation strengthening effects. However, in long-term use, an excessively high amount of Mo causes the coarsening of the precipitation phase and reduces the precipitation strengthening effect. Therefore, the content of Mo is controlled at 1.8 to 2.1%.

Nb is a stabilizing element of carbon and nitrogen, which can combine with carbon and nitrogen to form Nb(C, N), which inhibits the formation of carbon and nitride of chromium in steel and improves the intergranular corrosion resistance of stainless steel. In addition, Nb can also improve the high temperature strength of ferritic stainless steel through solid solution strengthening and precipitation strengthening. However, excessive Nb will cause the coarsening of the precipitates at high temperature and reduce the high temperature performance of the steel. Therefore, the Nb content is controlled at 0.2-0.5%.

Ti is also a stabilizing element of carbon and nitrogen, and can combine with carbon and nitrogen to form TiC or TiN, which inhibits the formation of chromium carbon and nitride in steel and improves the intergranular corrosion resistance of stainless steel. If the amount of Ti is too high, the processability of the material will be reduced due to the precipitation of excessive coarse TiC or TiN. Therefore, the content of Ti is controlled at 0.1-0.2%.

W is one of several alloying elements that has a significant effect on improving the thermal strength of the matrix. The high melting point metal tungsten dissolves into the matrix, hinders the diffusion of atoms and enhances the bonding force of atoms, so it can maintain the stability of the structure at high temperature, thereby improving the heat resistance of steel. In addition, the W element forms a precipitation phase in ferritic stainless steel, providing a precipitation strengthening effect. However, excessive W will cause the coarsening of the precipitates, which is detrimental to the high temperature performance. Therefore, the W content is controlled at 0.4 to 1.5%.

Rare earth Ce can promote the diffusion and migration of Cr, facilitate the formation of dense Cr ₂ O ₃ film, and improve the high temperature oxidation resistance of ferritic stainless steel. But too much Ce will increase the number of inclusions in the steel and reduce the toughness of the material. Therefore, the Ce content is controlled at 0.04-0.1%.

Mn can effectively inhibit the scale peeling and abnormal oxidation of stainless steel, and can also reduce the consumption of Cr and inhibit the formation of Cr-depleted regions. Excessive Mn content will destroy the corrosion resistance and workability of steel at room temperature. Therefore, the Mn content is controlled at 0.25 to 0.35%.

Both S and P elements are harmful elements that are inevitably mixed in steel, so the S content should not be higher than 0.005%, and the P content should be ≤ 0.01%.

Beneficial effects of the present invention:

The high-temperature strength of the stainless steel plate obtained by the preparation method of the invention exceeds that of the existing steel grade B444M2, and the formability is obviously better than that of the ferritic stainless steel of B444M2. This ferritic stainless steel is especially suitable for components such as automobile exhaust systems, and can cope with the working environment around 1100°C.

The ferritic stainless steel sheet of the present invention has good applicability due to its good high temperature strength and workability, and can be used for exhaust gas passage parts of power plants in addition to the processed products of exhaust system parts. Mo element is added, and it can also be used in a corrosion-resistant environment.

Description of drawings:

Figure 1 is a schematic diagram of the dimensions of a high temperature tensile specimen;

Fig. 2 is the ferritic stainless steel plate with good high temperature strength and good formability prepared in Example 2. Optical microscopic microstructure diagram;

Fig. 3 is the ferritic stainless steel plate with good high temperature strength and good formability prepared in Example 7. Optical microscopic microstructure diagram;

FIG. 4 is an optical microscopic metallographic structure diagram of the finished plate prepared in Comparative Example 7. FIG.

Detailed ways:

The present invention will be further described in detail below in conjunction with the examples.

In the embodiment of the present invention, a standard tensile sample is made according to GB/T228.1-2010, and the yield strength σ _0.2 , tensile strength σ _b and elongation after fracture δ of the material are measured on a CMT5105-SANS computer-controlled electronic universal testing machine, A schematic diagram of the dimensions of the high-temperature tensile specimen is shown in Figure 1.

In the example of the present invention, the tensile test is carried out according to the national standard GB/ _T5027-2016 , and the average plastic strain ratio rm and the degree of anisotropy Δr of the material are measured on a CMT5105-SANS computer-controlled electronic universal testing machine. Tensile specimens were prepared along the direction of 0°, 45° and 90° to the rolling direction of the plate, and the plastic strain ratios r _0° , r _45° and r _90° in each direction were measured on the tensile testing machine when the strain was 15%, Press r _m =(r ₀ +2r ₄₅ +r ₉₀ )/4

The plastic strain ratio is calculated, and the anisotropy degree is calculated according to Δr=(r ₀ -2r ₄₅ +r ₉₀ )/2.

In the embodiment of the present invention, the standard sample is cut along the direction of 0° to the rolling direction of the cold-rolled and annealed sheet, and the surface of the sample is sequentially used with 240#, 400#, 600#, 800#, 1000#, 1200#, 1500 # # water sandpaper to bright, and then after 15% tensile deformation, use TR300 portable roughness shape measuring instrument to measure the surface of the plate along the direction perpendicular to the rolling direction to obtain the average surface roughness Ra.

The high-temperature tensile specimens were made from the finished plates, and were subjected to a tensile test at 1100°C on an MMS-200 thermal simulation testing machine with a strain rate of 0.05min ^-1 to measure their tensile strength.

In the embodiment of the present invention, the specific parameters of the metallographic corrosion of the finished plate are: electrolytic corrosion by 60% HNO ₃ nitric acid aqueous solution, voltage 45V, time 60S.

Preliminary experiment:

The applicant conducts experiments by setting different hot-rolling annealing temperatures and cold-rolling annealing temperatures for different finishing rolling temperatures to obtain finished steel sheets, and finally determines the hot-rolling annealing temperature and cold-rolling annealing temperature range that satisfy the technical solution by testing the performance. The annealing temperature of hot rolling is 1025～1075℃, and the annealing temperature of cold rolling is 1025～1075℃.

Example 1

A ferritic stainless steel plate with good high temperature strength and formability, its composition is calculated by mass percentage, including C0.008%, N 0.008%, Cr 19.4%, Ti 0.14%, Nb 0.45%, Mo 2.03%, W 1.03% %, Si 0.52%, Mn 0.35%, Ce 0.049%, S 0.005%, P 0.008%, and the balance is Fe.

The preparation steps are as follows: the molten steel is smelted according to the set composition and cast into a steel ingot, and the composition by mass percentage is: C0.008%, N 0.008%, Cr 19.4%, Ti 0.14%, Nb 0.45%, Mo 2.03%, W 1.03% , Si 0.52%, Mn 0.35%, Ce 0.049%, S 0.005%, P 0.008%, and the balance is Fe. The ingot is forged into a slab, the forging temperature is 1200 ° C, and the forging is 40 mm. After the forging is completed, it is air-cooled to room temperature. Then, the air-cooled slab was heated to 1200°C, kept for 1 h, followed by 7 passes of hot rolling, the start rolling temperature was 1150°C, the final rolling temperature was 800°C, and the hot rolling was carried out to 5 mm (reduction ratio 87.5%), The single-pass reduction ratio of hot rolling is 30%, and after rolling, it is air-cooled to room temperature to make a hot-rolled sheet. The hot-rolled sheet was annealed at 1025°C for 5min, air-cooled to room temperature, and cold-rolled to 1mm after mechanical descaling (reduction rate was 80%), and the single-pass reduction rate of cold rolling did not exceed 10%, and annealed at 1050°C for 1min , a ferritic stainless steel plate with good high temperature strength and formability is made. The tensile strength σ _s of the steel plate at 1100 ° C is 21 MPa, the yield strength σ _0.2 at room temperature is 395 MPa, and the tensile strength σ _b at room temperature is 611 MPa. , the elongation after fracture at room temperature is δ29.9%, the average value of plastic strain ratio is r _m 1.57, the degree of anisotropy is Δr0.08, and the average surface roughness after 15% deformation along the rolling direction is R _a 0.9μm.

Example 2

A ferritic stainless steel plate with good high temperature strength and formability, its composition is calculated by mass percentage, including C0.008%, N 0.008%, Cr 19.4%, Ti 0.14%, Nb 0.45%, Mo 2.03%, W 1.03% %, Si 0.52%, Mn 0.35%, Ce 0.049%, S 0.005%, P 0.008%, and the balance is Fe.

The preparation steps are as follows: the molten steel is smelted according to the set composition and cast into a steel ingot, and the composition by mass percentage is: C0.008%, N 0.008%, Cr 19.4%, Ti 0.14%, Nb 0.45%, Mo 2.03%, W 1.03% , Si 0.52%, Mn 0.35%, Ce 0.049%, S 0.005%, P 0.008%, and the balance is Fe. The ingot is forged into a slab, the forging temperature is 1200 ° C, and the forging is 40 mm. After the forging is completed, it is air-cooled to room temperature. Then, the air-cooled slab was heated to 1200°C, kept for 1 h, followed by 7 passes of hot rolling, the start rolling temperature was 1150°C, the final rolling temperature was 800°C, and the hot rolling was carried out to 5 mm (reduction ratio 87.5%), The single-pass reduction ratio of hot rolling is 30%, and after rolling, it is air-cooled to room temperature to make a hot-rolled sheet. The hot-rolled sheet was annealed at 1050°C for 5min, air-cooled to room temperature, mechanically descaled and then cold-rolled to 1mm (reduction rate of 80%), and the single-pass reduction rate of cold rolling did not exceed 10%, and annealed at 1050°C for 1min , a ferritic stainless steel plate with good high temperature strength and formability is made. Its optical microstructure is shown in Figure 2. The tensile strength σ _s of the steel plate at 1100 ℃ is 20MPa, and the yield strength σ at room temperature is σ _0.2 is _394MPa , the tensile strength σb at room temperature is 610MPa, the elongation after fracture at room temperature is δ29.5%, the average plastic strain ratio r _m 1.62, the degree of anisotropy Δr-0.09, the deformation along the rolling direction is 15% % After surface roughness average value _Ra 0.92 μm.

Example 3

A ferritic stainless steel plate with good high temperature strength and formability, its composition is calculated by mass percentage, including C0.008%, N 0.008%, Cr 19.4%, Ti 0.14%, Nb 0.45%, Mo 2.03%, W 1.03% %, Si 0.52%, Mn 0.35%, Ce 0.049%, S 0.005%, P 0.008%, and the balance is Fe.

The preparation steps are as follows: the molten steel is smelted according to the set composition and cast into a steel ingot, and the composition by mass percentage is: C0.008%, N 0.008%, Cr 19.4%, Ti 0.14%, Nb 0.45%, Mo 2.03%, W 1.03% , Si 0.52%, Mn 0.35%, Ce 0.049%, S 0.005%, P 0.008%, and the balance is Fe. The ingot is forged into a slab, the forging temperature is 1200 ° C, and the forging is 40 mm. After the forging is completed, it is air-cooled to room temperature. Then, the air-cooled slab was heated to 1200°C, kept for 1 h, followed by 7 passes of hot rolling, the start rolling temperature was 1150°C, the final rolling temperature was 800°C, and the hot rolling was carried out to 5 mm (reduction ratio 87.5%), The single-pass reduction ratio of hot rolling is 30%, and after rolling, it is air-cooled to room temperature to make a hot-rolled sheet. The hot-rolled sheet was annealed at 1075℃ for 5min, air-cooled to room temperature, and then cold-rolled to 1mm after mechanical descaling (reduction rate was 80%). , a ferritic stainless steel plate with good high temperature strength and formability is made. The tensile strength σ _s of the steel plate at 1100 ° C is 20 MPa, the yield strength σ _0.2 at room temperature is 392 MPa, and the tensile strength σ _b at room temperature is 603 MPa. , the elongation after fracture at room temperature is δ30.1%, the average value of plastic strain ratio is r _m 1.68, the degree of anisotropy is Δr0.07, and the average surface roughness after 15% deformation along the rolling direction is R _a 0.88μm.

Example 4

A ferritic stainless steel plate with good high temperature strength and formability, its composition is calculated by mass percentage, including C0.008%, N 0.008%, Cr 19.4%, Ti 0.14%, Nb 0.45%, Mo 2.03%, W 1.03% %, Si 0.52%, Mn 0.35%, Ce 0.049%, S 0.005%, P 0.008%, and the balance is Fe.

The preparation steps are as follows: the molten steel is smelted according to the set composition and cast into a steel ingot, and the composition by mass percentage is: C0.008%, N 0.008%, Cr 19.4%, Ti 0.14%, Nb 0.45%, Mo 2.03%, W 1.03% , Si 0.52%, Mn 0.35%, Ce 0.049%, S 0.005%, P 0.008%, and the balance is Fe. The ingot is forged into a slab, the forging temperature is 1200 ° C, and the forging is 40 mm. After the forging is completed, it is air-cooled to room temperature. Then, the air-cooled slab was heated to 1200°C, kept for 1 h, followed by 7 passes of hot rolling, the start rolling temperature was 1100°C, the final rolling temperature was 900°C, and the hot rolling was carried out to 6 mm (reduction ratio 85%), The single pass reduction ratio of hot rolling is 20%, and after rolling, it is air-cooled to room temperature to make a hot-rolled sheet. The hot-rolled sheet was annealed at 1050°C for 6min, air-cooled to room temperature, mechanically descaled and then cold-rolled to 1mm (reduction rate of 83.3%), the reduction rate of a single pass of cold-rolling was not more than 10%, and annealed at 1025°C for 1min , a ferritic stainless steel plate with good high temperature strength and formability is made. The tensile strength σ _s of the steel plate at 1100 ° C is 21 MPa, the yield strength σ _0.2 at room temperature is 390 MPa, and the tensile strength σ _b at room temperature is 609 MPa. , the elongation after fracture at room temperature is δ29.3%, the average value of plastic strain ratio is r _m 1.52, the degree of anisotropy is Δr0.05, and the average surface roughness after 15% deformation along the rolling direction is R _a 0.48μm.

Example 5

A ferritic stainless steel plate with good high temperature strength and formability, its composition is calculated by mass percentage, including C0.008%, N 0.008%, Cr 19.4%, Ti 0.14%, Nb 0.45%, Mo 2.03%, W 1.03% %, Si 0.52%, Mn 0.35%, Ce 0.049%, S 0.005%, P 0.008%, and the balance is Fe.

The preparation steps are as follows: the molten steel is smelted according to the set composition and cast into a steel ingot, and the composition by mass percentage is: C0.008%, N 0.008%, Cr 19.4%, Ti 0.14%, Nb 0.45%, Mo 2.03%, W 1.03% , Si 0.52%, Mn 0.35%, Ce 0.049%, S 0.005%, P 0.008%, and the balance is Fe. The ingot is forged into a slab, the forging temperature is 1200 ° C, and the forging is 40 mm. After the forging is completed, it is air-cooled to room temperature. Then, the air-cooled slab was heated to 1200°C, kept for 1 h, followed by 7 passes of hot rolling, the start rolling temperature was 1100°C, the final rolling temperature was 900°C, and the hot rolling was carried out to 6 mm (reduction ratio 85%), The single pass reduction ratio of hot rolling is 20%, and after rolling, it is air-cooled to room temperature to make a hot-rolled sheet. The hot-rolled sheet was annealed at 1050°C for 6min, air-cooled to room temperature, and then mechanically descaled and then cold-rolled to 1mm (reduction rate 83.3%), and the single-pass reduction rate of cold rolling did not exceed 10%, and annealed at 1050°C for 1min , a ferritic stainless steel plate with good high temperature strength and formability is made. The tensile strength σ _s of the steel plate at 1100 ° C is 21 MPa, the yield strength σ _0.2 at room temperature is 387 MPa, and the tensile strength σ _b at room temperature is 600 MPa. , the elongation after fracture at room temperature is δ29.2%, the average value of plastic strain ratio is r _m 1.56, the degree of anisotropy is Δr 0.02, and the average surface roughness after 15% deformation along the rolling direction is R _a 0.35μm.

Example 6

A ferritic stainless steel plate with good high temperature strength and formability, its composition is calculated by mass percentage, including C0.008%, N 0.008%, Cr 19.4%, Ti 0.14%, Nb 0.45%, Mo 2.03%, W 1.03% %, Si 0.52%, Mn 0.35%, Ce 0.049%, S 0.005%, P 0.008%, and the balance is Fe.

The preparation steps are as follows: the molten steel is smelted according to the set composition and cast into a steel ingot, and the composition by mass percentage is: C0.008%, N 0.008%, Cr 19.4%, Ti 0.14%, Nb 0.45%, Mo 2.03%, W 1.03% , Si 0.52%, Mn 0.35%, Ce 0.049%, S 0.005%, P 0.008%, and the balance is Fe. The ingot is forged into a slab, the forging temperature is 1200 ° C, and the forging is 40 mm. After the forging is completed, it is air-cooled to room temperature. Then, the air-cooled slab was heated to 1200°C, kept for 1 h, followed by 7 passes of hot rolling, the start rolling temperature was 1100°C, the final rolling temperature was 900°C, and the hot rolling was carried out to 6 mm (reduction ratio 85%), The single pass reduction ratio of hot rolling is 20%, and after rolling, it is air-cooled to room temperature to make a hot-rolled sheet. The hot-rolled sheet was annealed at 1050°C for 6min, air-cooled to room temperature, and then cold-rolled to 1mm after mechanical descaling (reduction rate was 83.3%), and the single-pass reduction rate of cold rolling did not exceed 10%, and annealed at 1075°C for 1min , a ferritic stainless steel plate with good high temperature strength and formability is made. The tensile strength σ _s of the steel plate at 1100 ° C is 20 MPa, the yield strength σ _0.2 at room temperature is 383 MPa, and the tensile strength σ _b at room temperature is 596 MPa. , the elongation after fracture at room temperature is δ29.8%, the average value of plastic strain ratio is r _m 1.63, the degree of anisotropy is Δr0.09, and the average surface roughness after 15% deformation along the rolling direction is R _a 0.47μm.

Example 7

A ferritic stainless steel plate with good high temperature strength and formability, its composition is calculated by mass percentage, containing C0.007%, N 0.007%, Cr 19.5%, Ti 0.14%, Nb 0.44%, Mo 1.95%, W 0.58 %, Si 0.50%, Mn 0.32%, Ce 0.056%, S 0.004%, P 0.009%, and the balance is Fe.

The preparation steps are as follows: the molten steel is smelted according to the set composition and cast into a steel ingot, and the composition by mass percentage is: C0.007%, N 0.007%, Cr 19.5%, Ti 0.14%, Nb 0.44%, Mo 1.95%, W 0.58% , Si 0.50%, Mn 0.32%, Ce 0.056%, S 0.004%, P 0.009%, and the balance is Fe. The ingot is forged into a slab, the forging temperature is 1200 ° C, the forging is 60 mm, and after the forging is completed, it is air-cooled to room temperature. Then, the air-cooled slab was heated to 1200°C, kept for 1 h, followed by 7 passes of hot rolling, the starting rolling temperature was 1150°C, the final rolling temperature was 900°C, and the hot rolling was performed to 6 mm (reduction rate 90%), The single-pass reduction ratio of hot rolling is 30%, and after rolling, it is air-cooled to room temperature to make a hot-rolled sheet. The hot-rolled sheet was annealed at 1050°C for 4min, air-cooled to room temperature, and then mechanically descaled and then cold-rolled to 1.5mm (reduction rate of 75%), the reduction rate of a single pass of cold-rolling was not more than 10%, and annealed at 1050°C 1min, a ferritic stainless steel plate with good high temperature strength and formability is made. Its optical microscopic metallographic structure is shown in Figure 3. The tensile strength σ _s of the steel plate at 1100 °C is 18MPa, and the yield strength at room temperature is 18MPa. σ _0.2 is 382 MPa, tensile strength σ _b at room temperature is 588 MPa, elongation after fracture δ 31.2% at room temperature, average plastic strain ratio r _m 1.59, degree of anisotropy Δr 0.04, deformation along the rolling direction The average value of surface roughness after 15% is _Ra 0.66 μm.

Comparative Example 1

According to the composition of the ferritic stainless steel sheet of Example 1 (C 0.008%, N 0.008%, Cr 19.4%, Ti 0.14%, Nb 0.45%, Mo 2.03%, W 1.03%, Si 0.52%, Mn 0.35% , Ce 0.049%, S 0.005%, P 0.008%, the balance is Fe) smelted molten steel and cast into steel ingots, forged the steel ingots into slabs, the forging temperature is 1200 ℃, forged into 40mm, air-cooled to room temperature after forging is completed. Then, the air-cooled slab was heated to 1200°C, kept for 1 h, followed by 7 passes of hot rolling, the start rolling temperature was 1150°C, the final rolling temperature was 800°C, and the hot rolling was carried out to 5 mm (reduction ratio 87.5%), The reduction ratio of a single pass of hot rolling is 30%, and after rolling, it is air-cooled to room temperature to make a hot-rolled sheet. The hot-rolled sheet was annealed at 950°C for 5min, air-cooled to room temperature, mechanically descaled and then cold-rolled to 1mm (reduction rate of 80%), the reduction rate of a single pass of cold rolling did not exceed 10%, and annealed at 1050°C for 1min , made into a ferritic stainless steel plate, the yield strength σ _0.2 of the steel plate at room temperature is 403 MPa, the tensile strength σ _b at room temperature is 627 MPa, the elongation after fracture at room temperature δ 26.3%, the average value of plastic strain ratio r _m 1.27, degree of anisotropy Δr 0.35, average surface roughness after 15% deformation in the rolling direction R _a 1.70 μm.

Comparative Example 2

According to the composition of the ferritic stainless steel sheet of Example 1 (C 0.008%, N 0.008%, Cr 19.4%, Ti 0.14%, Nb 0.45%, Mo 2.03%, W 1.03%, Si 0.52%, Mn 0.35% , Ce 0.049%, S 0.005%, P 0.008%, the balance is Fe) smelted molten steel and cast into steel ingots, forged the steel ingots into slabs, the forging temperature is 1200 ℃, forged into 40mm, air-cooled to room temperature after forging is completed. Then, the air-cooled slab was heated to 1200°C, kept for 1 h, followed by 7 passes of hot rolling, the start rolling temperature was 1150°C, the final rolling temperature was 800°C, and the hot rolling was carried out to 5 mm (reduction ratio 87.5%), The single-pass reduction ratio of hot rolling is 30%, and after rolling, it is air-cooled to room temperature to make a hot-rolled sheet. The hot-rolled sheet was annealed at 1000°C for 5min, air-cooled to room temperature, and then cold-rolled to 1mm after mechanical descaling (reduction rate was 80%), and the single-pass reduction rate of cold rolling did not exceed 10%, and annealed at 1050°C for 1min , made into a ferritic stainless steel plate, the yield strength σ _0.2 of the steel plate at room temperature is 396 MPa, the tensile strength σ _b at room temperature is 613 MPa, the elongation after fracture at room temperature δ 27.9%, the average value of plastic strain ratio r _m 1.36, degree of anisotropy Δr 0.23, average surface roughness after 15% deformation in the rolling direction R _a 1.34 μm.

Comparative Example 3

According to the composition of the ferritic stainless steel sheet of Example 1 (C 0.008%, N 0.008%, Cr 19.4%, Ti 0.14%, Nb 0.45%, Mo 2.03%, W 1.03%, Si 0.52%, Mn 0.35% , Ce 0.049%, S 0.005%, P 0.008%, the balance is Fe) smelted molten steel and cast into steel ingots, forged the steel ingots into slabs, the forging temperature is 1200 ℃, forged into 40mm, air-cooled to room temperature after forging is completed. Then, the air-cooled slab was heated to 1200°C, kept for 1 h, followed by 7 passes of hot rolling, the start rolling temperature was 1150°C, the final rolling temperature was 800°C, and the hot rolling was carried out to 5 mm (reduction ratio 87.5%), The single-pass reduction ratio of hot rolling is 30%, and after rolling, it is air-cooled to room temperature to make a hot-rolled sheet. The hot-rolled sheet was annealed at 1100°C for 5min, air-cooled to room temperature, and then mechanically descaled and then cold-rolled to 1mm (reduction rate of 80%), the reduction rate of a single pass of cold-rolling was not more than 10%, and annealed at 1050°C for 1min , made into a ferritic stainless steel plate, the yield strength σ _0.2 of the steel plate at room temperature is 390 MPa, the tensile strength σ _b at room temperature is 600 MPa, the elongation after fracture at room temperature δ 30.3%, the average value of plastic strain ratio r _m 1.72, anisotropy Δr 0.16, average surface roughness _Ra 0.89 μm after 15% deformation in the rolling direction.

Comparative Example 4

According to the composition of the ferritic stainless steel sheet of Example 1 (C 0.008%, N 0.008%, Cr 19.4%, Ti 0.14%, Nb 0.45%, Mo 2.03%, W 1.03%, Si 0.52%, Mn 0.35% , Ce 0.049%, S 0.005%, P 0.008%, the balance is Fe) smelted molten steel and cast into steel ingots, forged the steel ingots into slabs, the forging temperature is 1200 ℃, forged into 40mm, air-cooled to room temperature after forging is completed. Then, the air-cooled slab was heated to 1200°C, kept for 1 h, followed by 7 passes of hot rolling, the start rolling temperature was 1100°C, the final rolling temperature was 900°C, and the hot rolling was carried out to 6 mm (reduction ratio 85%), The single pass reduction ratio of hot rolling is 20%, and after rolling, it is air-cooled to room temperature to make a hot-rolled sheet. The hot-rolled sheet was annealed at 1050°C for 6min, air-cooled to room temperature, and then mechanically descaled and then cold-rolled to 1mm (reduction rate 83.3%), with a single-pass reduction rate of no more than 10%, and annealed at 950°C for 1min , made into a ferritic stainless steel plate, the yield strength σ _0.2 at room temperature of the steel plate is 430 MPa, the tensile strength σ _b at room temperature is 643 MPa, the elongation after fracture at room temperature δ 17.4%, the average value of plastic strain ratio r _m 1.03, degree of anisotropy Δr-0.21, average surface roughness _Ra 0.73 μm after 15% deformation in the rolling direction.

Comparative Example 5

According to the composition of the ferritic stainless steel sheet of Example 1 (C 0.008%, N 0.008%, Cr 19.4%, Ti 0.14%, Nb 0.45%, Mo 2.03%, W 1.03%, Si 0.52%, Mn 0.35% , Ce 0.049%, S 0.005%, P 0.008%, the balance is Fe) smelted molten steel and cast into steel ingots, forged the steel ingots into slabs, the forging temperature is 1200 ℃, forged into 40mm, air-cooled to room temperature after forging is completed. Then, the air-cooled slab was heated to 1200°C, kept for 1 h, followed by 7 passes of hot rolling, the start rolling temperature was 1100°C, the final rolling temperature was 900°C, and the hot rolling was carried out to 6 mm (reduction ratio 85%), The single pass reduction ratio of hot rolling is 20%, and after rolling, it is air-cooled to room temperature to make a hot-rolled sheet. The hot-rolled sheet was annealed at 1050°C for 6min, air-cooled to room temperature, and then mechanically descaled and then cold-rolled to 1mm (reduction rate of 83.3%), and the single-pass reduction rate of cold rolling did not exceed 10%, and annealed at 1000°C for 1min , made into a ferritic stainless steel plate, the yield strength σ _0.2 of the steel plate at room temperature is 398 MPa, the tensile strength σ _b at room temperature is 617 MPa, the elongation after fracture at room temperature δ 25.6%, the average value of plastic strain ratio r _m 1.21, degree of anisotropy Δr-0.11, average surface roughness _Ra 0.53 μm after 15% deformation in the rolling direction.

Comparative Example 6

According to the composition of the ferritic stainless steel sheet of Example 1 (C 0.008%, N 0.008%, Cr 19.4%, Ti 0.14%, Nb 0.45%, Mo 2.03%, W 1.03%, Si 0.52%, Mn 0.35% , Ce 0.049%, S 0.005%, P 0.008%, the balance is Fe) smelted molten steel and cast into steel ingots, forged the steel ingots into slabs, the forging temperature is 1200 ℃, forged into 40mm, air-cooled to room temperature after forging is completed. Then, the air-cooled slab was heated to 1200°C, kept for 1 h, followed by 7 passes of hot rolling, the start rolling temperature was 1100°C, the final rolling temperature was 900°C, and the hot rolling was carried out to 6 mm (reduction ratio 85%), The single pass reduction ratio of hot rolling is 20%, and after rolling, it is air-cooled to room temperature to make a hot-rolled sheet. The hot-rolled sheet was annealed at 1050°C for 6min, air-cooled to room temperature, and cold-rolled to 1mm after mechanical descaling (reduction rate 83.3%), and the single-pass reduction rate of cold rolling did not exceed 10%, and annealed at 1100°C for 1min , made into a ferritic stainless steel plate, the yield strength σ _0.2 of the steel plate at room temperature is 383 MPa, the tensile strength σ _b at room temperature is 591 MPa, the elongation after fracture at room temperature δ 31.1%, the average value of plastic strain ratio r _m 1.72, degree of anisotropy Δr 0.18, average surface roughness after 15% deformation in the rolling direction R _a 0.85 μm.

Comparative Example 7

Taking the B444M2 type 5mm hot-rolled sheet currently produced and practically used as a comparison material, its composition by mass percentage is: C 0.007%, N 0.007%, Cr 19.3%, Ti 0.14%, Nb 0.46%, Mo 2.05%, Si 0.57 %, Mn 0.29%, S 0.005%, P 0.01%, the rest is Fe and inevitable impurities. The 5mm hot-rolled sheet was annealed at 1000°C for 10min, air-cooled to room temperature, cold-rolled to 1mm after mechanical descaling, and annealed at 1000°C for 2min to make a finished sheet. Its optical microscopic metallographic structure is shown in Figure 4. The tensile strength of the steel sheet at 1100°C is 14MP, the yield strength σ _0.2 at room temperature is 360 MPa, the tensile strength σ _b at room temperature is 569 MPa, the elongation after fracture at room temperature δ 28.1%, the average value of plastic strain ratio r _m 1.31, degree of anisotropy Δr 0.25, average surface roughness _Ra 0.94 μm after 15% deformation in the rolling direction.

Formability:

Table 1 shows the formability and mechanical properties of the finished plates obtained from the above Examples 1 to 7 and Comparative Examples 1 to 7.

At the same time, if the average plastic strain ratio r _m ≥ 1.4, the degree of anisotropy Δr < 0.1, the average surface roughness Ra < 1 μm, and the elongation after fracture ≥ 28% are regarded as acceptable (○), those not met are regarded as not Passed (×).

Evaluation results

From Table 1 and the high temperature strength test results, it is clearly known that the ferritic stainless steel plate produced according to the composition and preparation method designed in the present invention has significantly better formability and high temperature strength than the B444M2 ferritic stainless steel currently produced and applied.

Table 1

Claims (5)

1. The preparation method of the ferrite stainless steel plate with good high-temperature strength and forming performance is characterized in that the ferrite stainless steel plate comprises the following components in percentage by mass, that is, less than or equal to 0.01% of C, 0.006-0.01% of N, 0.4-0.6% of Si,cr 18-20%, Mo 1.8-2.1%, Nb 0.2-0.5%, Ti 0.1-0.2%, W0.4-1.5%, Ce 0.04-0.1%, Mn 0.25-0.35%, S less than or equal to 0.005%, P less than or equal to 0.01%, and the balance of Fe; the ferritic stainless steel plate with good high-temperature strength and forming performance has tensile strength sigma at 1100 DEG C_s20-21MPa, yield strength at room temperature_0.2392-394MPa, tensile strength at room temperature_b603-611MPa, elongation after fracture at room temperature29.5-30.1%, average value of plastic strain ratior _mNot less than 1.4, degree of anisotropy △rLess than or equal to 0.1, and surface roughness average value after deformation of 15% along rolling directionR _a≤1μm；

The preparation method comprises the following steps:

(1) smelting molten steel according to the set components and casting the molten steel into steel ingots, wherein the components comprise, by mass, less than or equal to 0.01% of C, 0.006-0.01% of N, 0.4-0.6% of Si, 18-20% of Cr, 1.8-2.1% of Mo, 0.2-0.5% of Nb, 0.1-0.2% of Ti, 0.4-1.5% of W, 0.04-0.1% of Ce, 0.25-0.35% of Mn, less than or equal to 0.005% of S, less than or equal to 0.01% of P, and the balance of Fe;

(2) forging the steel ingot into a plate blank, wherein the forging temperature is 1200-1250 ℃, and air-cooling to room temperature after the forging is finished;

(3) heating the air-cooled plate blank to 1150-1250 ℃, preserving heat for 1-3 h, performing hot rolling for 6-8 times, wherein the initial rolling temperature is 1100-1150 ℃, the final rolling temperature is 800 ℃, the total reduction rate is 85-90%, and air cooling to room temperature after hot rolling is completed;

(4) annealing the air-cooled hot rolled plate at 1025-1075 ℃ for 3-8 min, and then air-cooling to room temperature;

(5) and (2) cold rolling the hot-rolled annealed plate at room temperature, wherein the total reduction rate is 75-85%, annealing treatment is carried out at 1050 ℃ after the cold rolling is finished, the annealing time is 1-3 min, and the annealed plate is air-cooled to room temperature to prepare the ferritic stainless steel plate with good high-temperature strength and forming performance.

2. The method according to claim 1, wherein the thickness of the forged slab in the step (2) is 40 to 60 mm.

3. The method according to claim 1, wherein the hot rolling is performed at a reduction ratio of 20 to 40% per pass in the step (3).

4. The method of claim 1, wherein the step (5) comprises a step of cold rolling at a reduction ratio of 10% or less.

5. The method according to claim 1, wherein the thickness of the ferritic stainless steel sheet having excellent high-temperature strength and formability produced in the step (5) is 1 to 2 mm.

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