A 301L stainless steel chilled plate for high-speed trains and its preparation method

Abstract

The present invention belongs to the technical field of train metal material preparation, and in particular relates to a 301L stainless steel chilled plate for high-speed trains and a preparation method thereof, comprising: C≤0.03%, Si: 0.40%~1.00%, Mn≤2.0%, P≤0.045%, S≤0.03%, Cr: 16.00%~18.00%, Ni: 6.00%~8.00%, N: 0.10%~0.20%, Cu≤0.5%, and the rest being Fe and unavoidable impurities. The preparation method comprises the following contents: (1) adjusting the rolling process: adopting a double rolling process, the first rolling process: the total number of passes is 5-7; the finished rolling process: the total deformation rate of the finished rolling process is designed according to different strength levels; (2) adjusting the rolling mill parameters: optimizing the taper length and taper of the first intermediate roll, the convexity of the second intermediate roll and the working roll; (3) adjusting the cold line process: subjecting the first rolling process cold-rolled strip to solid solution and pickling treatment, and subjecting the finished rolling process cold-hardened strip to pickling, stretching and straightening treatment. This method can avoid the problems of edge wave plate shape defects and large performance fluctuations.

Description

Technical Field

[0001] The present invention belongs to the technical field of train metal material preparation, and in particular relates to a 301L stainless steel chilled plate for high-speed trains and a preparation method thereof. Background Art

[0002] 301L stainless steel chilled plates are widely used in various high-speed train structural parts, and the market demand is increasing year by year. However, customers have extremely high requirements for the plate shape, surface, and performance of this product. The plate unevenness must be ≤5mm / m, the surface must not have defects that cannot be polished away, and the mechanical properties must be precise.

[0003] 301L stainless steel chilled plate products are divided into two grades, MT and HT, according to tensile strength. After rolling, 301L stainless steel chilled plate with a thickness of ≥2.5mm is not annealed in the wide cold line process, but only pickled, flattened, and straightened. During the production process, problems such as edge wave plate defects and large performance fluctuations occur, which cannot meet customers' increasingly precise requirements. Summary of the Invention

[0004] The purpose of the present invention is to provide a 301L stainless steel chilled plate for high-speed trains and a preparation method thereof, so as to solve the problems of edge wave plate shape defects and large performance fluctuations occurring during the production process.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A 301L stainless steel chilled plate for high-speed trains has the following chemical compositions, measured by weight: C ≤ 0.03%, Si: 0.40% to 1.00%, Mn ≤ 2.0%, P ≤ 0.045%, S ≤ 0.03%, Cr: 16.00% to 18.00%, Ni: 6.00% to 8.00%, N: 0.10% to 0.20%, Cu ≤ 0.5%, and the remainder being Fe and unavoidable impurities.

[0007] The method for preparing the 301L stainless steel chilled plate for high-speed trains comprises the following steps:

[0008] (1) Adjust the rolling process: adopt the double rolling process, the first rolling process: the total number of passes is 5-7, the target curve of the plate shape of each pass is "U" shape, and the actual stress deviation value of the edge plate shape is controlled at 40~100N / mm 2 The actual stress deviation value of the middle plate shape is controlled within -30~0N / mm 2The total deformation rate of the first rolling process is controlled at 30-45%; the second rolling process (finished product rolling process): the total deformation rate of the finished product rolling process is designed according to different strength levels. The MT strength level series with thickness specifications of less than 5.0mm adopts one-pass rolling. The target plate shape curve is wavy, and the actual stress deviation value of the edge plate shape is controlled at 20~40N / mm 2 The actual stress deviation value of the middle plate shape is controlled within 0~20N / mm 2 , rolling speed ≤ 50m / min; MT strength above ≥5.0mm and all HT strength are all rolled in two passes, the deformation rate of the last pass is controlled at 2~6%, the target curve of the plate shape in the first rolling pass is "U" shape, and the actual stress deviation value of the edge plate shape is controlled at 20~40N / mm 2 The actual stress deviation value of the middle plate shape is controlled within -10~0N / mm 2 The target curve of the rolled product shape is wavy, and the actual stress deviation of the edge shape is controlled at 20~40N / mm. 2 The actual stress deviation value of the middle plate shape is controlled within the range of 0~20N / mm 2 Within the range, the first pass rolling speed is controlled ≤ 100m / min, the finished pass rolling speed is controlled ≤ 50m / min, the total deformation rate of the finished product with strength level MT is 6.0~7.0%, and the total deformation rate of the finished product with strength level HT is 16.0~19.0%;

[0009] (2) Adjust the rolling mill parameters: optimize the taper length and taper of the first intermediate roll, the crown of the second intermediate roll and the work roll. The taper length is 570 mm, the shape of the 0-420 mm position is a straight taper, the taper length: taper height is 1:0.001-0.002, the shape of the 420-570 mm position is a straight taper, the taper length: taper height is 1:0.0002-0.0004; the crown of the second intermediate roll is selected to be 0.25-0.35 mm, and the crown of the work roll is selected to be 0.05-0.15 mm;

[0010] (3) Adjust the cold line process: perform solid solution and pickling treatment on the cold-rolled strip in the first rolling process, and perform pickling, bending and straightening treatment on the cold-hardened strip in the finished rolling process.

[0011] During the solution treatment of the first rolling process in the (3) cold line process, the plate temperature is controlled at 1080~1110℃, and the holding time is 0.8~1.0min / mm; when the cold line process produces the finished rolled cold hardened strip steel, the furnace temperature is ≤400℃, the tensile straightening tension is 50~90 tons, and the elongation is 0.5%~2.0%.

[0012] The straightening treatment in (3) is carried out using a straightening machine, which includes three sets of straightening rollers. The pressing amounts of the three straightening rollers from right to left are 40-50 mm, 20-40 mm and 20-40 mm respectively.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] (1) By optimizing the chemical composition, the raw material composition in the cold rolling process is precisely adjusted to form a martensitic structure during the cold rolling process and achieve the final performance indicators;

[0015] (2) By adjusting the rolling process, rolling mill parameters and roll shape design during the rolling process, the rolling process and the target plate shape curve are matched, ensuring that the performance and plate shape of the finished product are precisely controlled at the same time, ensuring that the strip shape after rolling is straight and the thickness is accurate, and avoiding edge wave shape defects and large performance fluctuations;

[0016] (3) By standardizing the solid solution and tensile straightening processes in the first rolling process of the cold line process, the actual plate shape is improved to the greatest extent, ensuring that the plate shape unevenness reaches ≤5mm / m. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the target curve of plate shape during the first rolling process in the rolling process;

[0018] Figure 2 It is the target curve of plate shape during the rolling of finished product in the rolling process. DETAILED DESCRIPTION

[0019] The embodiments of the present invention are described in detail below with reference to the embodiments and drawings.

[0020] A roll of 301LHT stainless steel chilled plate with a specification of 4.0*1265mm is produced. The chemical composition, in weight percentage, includes: C: 0.020%, Si: 0.517%, Mn: 1.051%, P: 0.027%, S: 0.001%, Cr: 17.102%, Ni: 7.079%, N: 0.103%, Cu: 0.028%, and the rest is Fe and unavoidable impurities. The product is produced using a double-pass process, with the first pass rolling 7.806mm to 4.82mm and the finished product rolling 4.82mm to 3.95mm. A SUNDWING SFC 20H-406×1625 model 20-high mill is used, with a composite cone intermediate roll of 570mm in length. The 0-420mm position is a straight cone with a cone length: cone height ratio of 1:0.0015, and the 420-570mm position is a straight cone with a cone length: cone height ratio of 1:0.0003. The crown of the second intermediate roll is 0.30mm, and the crown of the work roll is 0.10mm. In the first pass, there are 5 passes in total, and the target curve of the plate shape for each pass is as follows: Figure 1 As shown in the figure, the actual stress deviation values ​​of the edge plate shape in the 1st to 5th passes are 80, 65, 50, 45 and 40 N / mm respectively. 2The actual stress deviation values ​​of the plate shape in the middle of the 1st to 5th passes are controlled at -30, -25, -10, -5 and 0 N / mm 2 The first rolling process is to roll the steel coil to a thickness of 4.82mm. Solution treatment and pickling treatment are carried out in the cold line. The plate temperature is controlled at 1100℃ and the holding time is 0.95min / mm. After the cold line production is completed, it is rolled on the SUNDWING SFC 20H-406×1625 model 20-high rolling mill for the second rolling process. Two passes are adopted. The first pass is 13.55%, and the deformation rate of the finished product pass is controlled at 5.2%. The target curve of the plate shape of the first rolling pass is as follows Figure 1 As shown, the actual stress deviation value of the edge plate is controlled at 30N / mm 2 The actual stress deviation value of the middle plate shape is controlled at -5N / mm 2 ; The target curve of finished product pass shape is as follows Figure 2 As shown, the actual stress deviation value of the edge plate is controlled at 30N / mm 2 The actual stress deviation value of the middle plate shape is controlled at 10N / mm 2 The rolling speed of the first pass is 80m / min, and the rolling speed of the finished product pass is 50m / min. After the cold-hardened plate is rolled, it is put on the cold line again for pickling and stretching and straightening treatment. The furnace temperature is 356℃. The stretching tension of the straightening treatment is 60 tons, and the elongation is 0.8%. The straightening unit has three sets of straightening rollers, and the reduction amounts are 45mm, 40mm and 40mm respectively.

[0021] The mechanical properties of the 4.0*1265mm 301LHT stainless steel chilled plate meet the requirements, and the plate unevenness reaches 3mm / m.

[0022] After adopting the method of the present invention, thick-gauge cold-hardened 301L stainless steel plates for high-speed trains were successfully prepared, meeting customer needs, with a performance compliance rate of 100% and a plate unevenness of ≤5 mm / m.

Claims

1. A method for preparing a 301L stainless steel chilled plate for high-speed trains, wherein the chemical composition of the 301L stainless steel chilled plate for high-speed trains is calculated in percentage by weight and comprises: C≤0.03%, Si: 0.40%~1.00%, Mn≤2.0%, P≤0.045%, S≤0.03%, Cr: 16.00%~18.00%, Ni: 6.00%~8.00%, N: 0.10%~0.20%, Cu≤0.5%, the rest are Fe and unavoidable impurities, characterized by including the following: (1) Adjust the rolling process: adopt the double rolling process, the first rolling process: the total number of passes is 5-7, the target curve of the plate shape of each pass is "U" shape, and the actual stress deviation value of the edge plate shape is controlled at 40~100N / mm 2 The actual stress deviation value of the middle plate shape is controlled within -30~0N / mm 2 The total deformation rate of the first rolling process is controlled at 30-45%; the second rolling process is the finished product rolling process: the total deformation rate of the finished product rolling process is designed according to different strength levels. The MT strength level series with thickness specifications of less than 5.0mm adopts one-pass rolling. The target plate shape curve is wavy, and the actual stress deviation value of the edge plate shape is controlled at 20~40N / mm 2 The actual stress deviation value of the middle plate shape is controlled within 0~20N / mm 2 , rolling speed ≤ 50m / min; MT strength above ≥5.0mm and all HT strength are all rolled in two passes, the deformation rate of the last pass is controlled at 2~6%, the target curve of the plate shape in the first rolling pass is "U" shape, and the actual stress deviation value of the edge plate shape is controlled at 20~40N / mm 2 The actual stress deviation value of the middle plate shape is controlled within -10~0N / mm 2 The target curve of the rolled product shape is wavy, and the actual stress deviation of the edge shape is controlled at 20~40N / mm. 2 The actual stress deviation value of the middle plate shape is controlled within the range of 0~20N / mm 2 Within the range, the first pass rolling speed is controlled ≤ 100m / min, the finished pass rolling speed is controlled ≤ 50m / min, the total deformation rate of the finished product with strength level MT is 6.0~7.0%, and the total deformation rate of the finished product with strength level HT is 16.0~19.0%; (2) Adjust the rolling mill parameters: optimize the taper length and taper of the first intermediate roll, the crown of the second intermediate roll and the work roll. The taper length is 570 mm, the shape of the 0-420 mm position is a straight taper, the taper length: taper height is 1:0.001-0.002, the shape of the 420-570 mm position is a straight taper, the taper length: taper height is 1:0.0002-0.0004; the crown of the second intermediate roll is selected to be 0.25-0.35 mm, and the crown of the work roll is selected to be 0.05-0.15 mm; (3) Adjust the cold line process: perform solid solution and pickling treatment on the cold-rolled strip in the first rolling process, and perform pickling, bending and straightening treatment on the cold-hardened strip in the finished rolling process.

2. The method for preparing a 301L stainless steel chilled plate for high-speed trains according to claim 1, characterized in that: During the solution treatment of the first rolling process in the (3) cold line process, the plate temperature is controlled at 1080~1110℃, and the holding time is 0.8~1.0min / mm; when the cold line process produces the finished rolled cold hardened strip steel, the furnace temperature is ≤400℃, the straightening tension of the bending and straightening treatment is 50~90 tons, and the elongation is 0.5%~2.0%.

3. The method for preparing a 301L stainless steel chilled plate for high-speed trains according to claim 2, characterized in that: The straightening treatment in (3) is carried out using a straightening machine, which includes three sets of straightening rollers. The pressing amounts of the three straightening rollers from right to left are 40-50 mm, 20-40 mm and 20-40 mm respectively.

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