Production method of high-yield-strength and high-elongation 316L stainless steel

Abstract

The invention provides a production method of 316L stainless steel with high yield strength and high elongation. The production method comprises the following steps: (1) preparing the following components in percentage by weight: 0.005 to 0.025 percent of C, 1.0 to 1.5 percent of Mn, 0.4 to 0.7 percent of Si, 16.5 to 18.0 percent of Cr, 10 to 11 percent of Ni, 0.07 to 0.1 percent of N and 2.0 to 2.5 percent of Mo; (2) smelting and casting to obtain a continuous casting billet; (3) carrying out hot rolling on the continuous casting billet to obtain a hot-rolled plate, wherein the finish rolling temperature of hot rolling is controlled at 930 + / -50 DEG C; and (4) the hot-rolled plate is sequentially subjected to solution annealing treatment, scale breaking and shot blasting acid pickling treatment, the solution annealing temperature is 1140 DEG C + / -20 DEG C, the elongation of a scale breaking mill is controlled to be 0.7% + / -0.3%, and the 316L stainless steel white-skin roll is obtained after acid pickling, so that steel can be properly thinned by the downstream without affecting the use function of downstream products.

Description

Technical Field

[0001] The invention relates to a steel smelting process, and in particular to a production method of 316L stainless steel with high yield strength and high elongation. Background Art

[0002] 316L stainless steel is a kind of austenitic stainless steel with good corrosion resistance and is widely used in the field of industrial plates. Under the composition and production process conditions of conventional 316L stainless steel, the yield strength at room temperature is an average of 270Mpa, the elongation is 52%, and the yield strength at high temperature of 130℃ is an average of 230Mpa. Although it has 100% met the European standard (yield strength above 220Mpa, elongation above 40%), the price of 316L stainless steel is relatively high. If the yield strength of the steel can be improved without reducing the toughness of the steel (the higher the elongation of the steel, the better its toughness), the steel can be appropriately thinned during downstream processing without affecting the use function of the downstream products, which is conducive to reducing the use cost and weight of the products. Based on this assumption, some customers have put forward new requirements for the yield strength and elongation of 316L stainless steel: yield strength above 290Mpa, elongation above 48% and yield strength above 245Mpa at high temperature of 130℃. According to statistics, only about 30% of the 316L stainless steel plates produced by conventional processes can meet the new requirements (i.e., the pass rate is about 30%). The pass rate is low and needs to be improved. Summary of the invention

[0003] The object of the present invention is to provide a production method of 316L stainless steel with high yield strength and high elongation.

[0004] The technical solution to achieve the purpose of the present invention is: a method for producing high yield strength and high elongation 316L stainless steel, comprising the following steps: (1) Ingredients (weight percentage wt%): C: 0.005-0.025%, Mn: 1.0-1.5%, Si: 0.4-0.7%, P: ≤0.045%, S: ≤0.015%, Cr: 16.5-18.0%, Ni: 10-11, N: 0.07-0.1%, Mo: 2.0-2.5%, the rest is iron and unavoidable impurities; (2) Smelting and casting: Smelting and casting the ingredients in step (1) in a converter to obtain a continuous casting billet; (3) hot rolling: hot rolling the continuous casting slab obtained in step (2) to obtain a hot rolled plate, wherein the final rolling temperature of the hot rolling is controlled at 930°C ± 50°C; (4) Solution annealing, scale breaking, shot blasting and pickling: The hot-rolled plate obtained in step (3) is sequentially subjected to solution annealing, scale breaking and shot blasting and pickling, wherein the solution annealing temperature is 1140°C ± 20°C, the elongation of the scale breaking machine is controlled at 0.7% ± 0.3%, and the 316L stainless steel white coil is obtained after pickling.

[0005] The present invention first increases the Si and N elements in a small amount in the composition design, controls the Si element of 316L stainless steel to 0.4-0.7%, and the N element to 0.07-0.1%, which can increase the room temperature yield strength of the white coil to an average value of 293Mpa. However, simply adjusting the composition design will increase the yield strength of the stainless steel material while also causing a decrease in the elongation of the material. The general operation to increase the elongation of the material is to reduce the temperature of the solution annealing. However, adjusting the solution annealing temperature requires scheduling conversion of the production process, which is more troublesome. The general function of the descaling machine is to peel off and shape the rust. Therefore, the elongation of the descaling machine in the production of 316L stainless steel is usually selected to be 0.1%-0.3%. However, the inventor unexpectedly discovered during practice that the elongation of the scale breaker is increased to 0.7%±0.3%, which can significantly improve the yield strength of the material. At the same time, the strain energy storage of the black coil after hot rolling can be increased by reducing the final rolling FDT temperature of hot rolling (from the target 1000℃ to 930℃±50℃), so that the subsequent solution annealing can be more sufficient. Therefore, even if the solution annealing temperature of conventional 316L stainless steel (1140℃±20℃) is used, the purpose of improving the toughness of the material without reducing its toughness can be achieved while increasing the yield strength. Therefore, while optimizing the composition design, the inventors further increased the room temperature yield strength of the white coil by applying an elongation of 0.7%±0.3% to the scale breaker in the scale breaking step, and adjusted the final rolling FDT temperature of the hot rolling, and the average value was increased to 310Mpa, thereby ensuring that the yield strength 100% meets: room temperature yield strength of more than 290Mpa and yield strength of more than 245Mpa at high temperature of 130°C. At the same time, the elongation of the white coil 100% meets: elongation of more than 48%. Only about 30% of the 316L stainless steel plates produced by conventional processes can meet the requirements of "room temperature yield strength of more than 290Mpa and yield strength of more than 245Mpa at high temperature of 130°C, and elongation of more than 48%". Since the present invention can ensure that the 316L stainless steel white coil produced meets the customer's requirements of "yield strength of more than 290Mpa, elongation of more than 48% and yield strength of more than 245Mpa at high temperature of 130°C", that is, the yield strength of 316L stainless steel white coils of the same thickness is higher while the toughness is not reduced, when downstream customers reprocess the 316L stainless steel white coils, they can appropriately thin the steel as needed without affecting the product's use function, which will help reduce the product's use cost and weight. In addition, the present invention increases the N content and helps improve corrosion resistance, ensuring the good corrosion resistance of 316L stainless steel. DETAILED DESCRIPTION

[0006] The specific implementation method of the production method of high yield strength and high elongation 316L stainless steel of the present invention is described in detail below: A method for producing high yield strength and high elongation 316L stainless steel comprises the following steps: (1) Ingredients (weight percentage wt%): C: 0.005-0.025%, Mn: 1.0-1.5%, Si: 0.4-0.7%, P: ≤0.045%, S: ≤0.015%, Cr: 16.5-18.0%, Ni: 10-11, N: 0.07-0.1%, Mo: 2.0-2.5%, the rest is iron and unavoidable impurities; (2) Smelting and casting: The ingredients in step (1) are smelted and cast in a converter to obtain a continuous casting billet; (3) hot rolling: hot rolling the continuous casting slab obtained in step (2) to obtain a hot rolled plate, wherein the final rolling temperature of the hot rolling is controlled at 930°C ± 50°C; (4) Solution annealing, scale breaking, shot blasting and pickling: The hot-rolled plate obtained in step (3) is sequentially subjected to solution annealing, scale breaking and shot blasting and pickling, wherein the solution annealing temperature is 1140°C ± 20°C, the elongation of the scale breaking machine is controlled at 0.7% ± 0.3%, and the 316L stainless steel white coil is obtained after pickling.

[0007] The composition design and key process parameters of Examples 1 to 10 of the production method of 316L stainless steel with high yield strength and high elongation of the present invention are shown in Tables 1 and 2, respectively. Among them, the composition design of Comparative Example 1 meets the requirements of this application, but the hot rolling final rolling temperature and the elongation of the scale breaker in the key process parameters do not meet the requirements of this application; the composition design of Comparative Examples 2 to 4 meets the requirements of this application, but the elongation of the scale breaker in the key process parameters does not meet the requirements of this application.

[0008] Table 1

[0009] Table 2

[0010] The yield strength and elongation of the finished 316L stainless steel white coils obtained in Examples 1 to 10 and Comparative Examples 1 to 4 were measured, and the test data are shown in Table 3.

[0011] Table 3

[0012] It can be seen from Tables 1 to 3 that through the comprehensive adjustment of the component design and main process steps of the present invention, the room temperature yield strength of 316L stainless steel can be increased to more than 306 MPa, the elongation is more than 50%, and the yield strength at a high temperature of 130°C is more than 250 MPa. The embodiment can 100% meet the customer's requirements of "yield strength of more than 290 MPa, elongation of more than 48% and yield strength of more than 245 MPa at a high temperature of 130°C", and the qualified rate is increased to 100%, so that when the 316L stainless steel white paper coil is reprocessed downstream, it can be thinned as needed without affecting the use function of the product, which will be beneficial to reducing the use cost and weight of the product; when the elongation of the scale breaker is lower than 0.4%, the room temperature yield strength and the yield strength at a high temperature of 130°C cannot meet the requirements of this application.

[0013] When the elongation of the scale breaker exceeds 1%, slight roller marks will be left on the surface of the stainless steel material after the scale is broken, which increases the trouble of polishing the surface when the stainless steel material is used; and it is also easy to cause damage to the scale breaking roller. Therefore, the elongation of the scale breaker is controlled within 0.7%±0.3% in the present invention.

[0014] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent process changes made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for producing high yield strength and high elongation 316L stainless steel, characterized in that: The following steps are involved: (1) Ingredients (weight percentage wt%): C: 0.005-0.025%, Mn: 1.0-1.5%, Si: 0.4-0.7%, P: ≤0.045%, S: ≤0.015%, Cr: 16.5-18.0%, Ni: 10-11, N: 0.07-0.1%, Mo: 2.0-2.5%, the rest is iron and unavoidable impurities; (2) Smelting and casting: Smelting and casting the ingredients in step (1) in a converter to obtain a continuous casting billet; (3) hot rolling: hot rolling the continuous casting slab obtained in step (2) to obtain a hot rolled plate, wherein the final rolling temperature of the hot rolling is controlled at 930°C ± 50°C; (4) Solution annealing, scale breaking, shot blasting and pickling: The hot-rolled plate obtained in step (3) is sequentially subjected to solution annealing, scale breaking and shot blasting and pickling, wherein the solution annealing temperature is 1140°C ± 20°C, the elongation of the scale breaking machine is controlled at 0.7% ± 0.3%, and the 316L stainless steel white coil is obtained after pickling.

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