Cold rolling process of austenitic stainless steel 2b material for high quality surface finish

Abstract

The application discloses a high-quality surface-decorating austenitic stainless steel 2B material cold rolling process and relates to the technical field of stainless steel surface treatment. The application modifies the surface oxide scale of the austenitic stainless steel by selecting a reasonable heat treatment temperature for the hot-rolled black coil, refines the grains to increase the surface hardness of the steel coil, does not perform annealing after the cold rolling mill rolls to a certain thickness, directly adopts chromium steel wire pickling treatment, further removes the surface layer defects of the raw material to achieve surface quality homogenization, then directly performs cold rolling to the target thickness, finally adopts reasonable heat treatment, electrolytic pickling process and performs flattening treatment through an online flattening mill to produce the 2B product with high-quality surface requirements.

Description

Technical Field

[0001] This invention relates to the field of stainless steel surface treatment technology, and in particular to a cold rolling process for high-quality austenitic stainless steel 2B material for surface decoration. Background Technology

[0002] Conventional austenitic stainless steel undergoes high-temperature annealing, followed by pickling with neutral salt electrolysis and a medium-to-high concentration mixed acid (a mixture of nitric acid and hydrofluoric acid) for good results. However, this pickling process thoroughly removes the Cr-depleted regions at the grain boundaries and the Cr-depleted layer at the interface between the matrix and oxide scale, resulting in high surface roughness and grain boundary corrosion grooves. Due to this roughness, light is diffusely reflected, causing the austenitic stainless steel surface to appear generally whitish to the naked eye. Currently, high-end decorative austenitic stainless steels primarily used are 304, 316L, and 904L, requiring grinding and polishing. The presence of grain boundary corrosion grooves on the surface of conventional 2B austenitic stainless steel increases the cost of grinding and polishing. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a cold rolling process for high-quality austenitic stainless steel 2B material for surface decoration, which solves the problem that austenitic stainless steel 2B raw materials are prone to defects such as white spots and bright spots after grinding and polishing, making them unsuitable for high-end surface decoration applications.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows: A cold rolling process for high-quality austenitic stainless steel 2B for surface decoration includes the following steps: S1. Annealing and pickling of hot-rolled austenitic black coils with a thickness of 4.5-5.5mm: six-roll mill rolling is performed, with the rolling reduction rate controlled between 10% and 15%. After rolling, annealing is performed, and after annealing, a continuous pickling process of descaling-shot blasting-sulfuric acid pre-pickling-mixed acid pickling is used for pickling. S2, 20-roll mill pre-rolling: The thickness of the steel coil processed in step S1 is pre-rolled to an intermediate thickness of 2.0mm to 3.5mm using a 20-roll mill, and the rolling reduction rate is controlled at 25% to 60% to obtain a pre-rolled hardened steel coil. S3. Pickling treatment of chrome steel wire: The steel coil after step S2 is first degreased and deoiled, and then the surface of the chrome steel wire is treated. S4, 20-roll mill rolling: The steel coil processed in step S3 is rolled to a final thickness of 0.8mm to 2.0mm, with the rolling reduction rate controlled at 25% to 60%; S5. Cold annealing and pickling treatment: The hardened steel coil after step S4 is first degreased, then annealed, and then subjected to neutral salt electrolytic pickling treatment. S6. Online leveling: The steel coil processed in step S5 is leveled to obtain high-quality decorative austenitic stainless steel 2B surface material. S7, ETD Slitting Processing: The materials produced in the previous process are processed according to customer requirements to determine the length, width, and weight, and then packaged and stored.

[0005] Furthermore, in step S1, the annealing process adopts a furnace temperature control mode, with the furnace temperature set between 1020℃ and 1050℃ throughout the process, and a TV value of 160 to 180 mm•m / min. In the continuous pickling process, the scale-breaking machine adopts an extension mode, with an elongation rate of 1% to 1.5%. The shot blasting uses 0.5 to 0.8 mm diameter full-cast shot, with the blasting speed controlled at 45 to 54 m / s and the flow rate controlled at 8 to 12 kg / m³. 2 The phosphorus removal speed of the two sets of sulfuric acid pre-washing brushes is controlled at level 5 to 7; the mixed acid concentration of the mixed acid wash is controlled at 120 to 130 g / L for nitric acid and 25 to 30 g / L for hydrofluoric acid, and the acid temperature is controlled at 45 to 50℃.

[0006] Furthermore, in step S2, the rolling rolls are selected from M42 high-speed steel rolls. The rolling speed is limited to 120-150 m / min for the first pass, 80-120 m / min for the last pass, and there is no speed limit for the remaining passes. The rolling oil flow rate is controlled at 2500-3500 L / min.

[0007] Further, in step S3, the elongation rate of the scale-breaking machine for surface treatment of chromium steel wire is set between 1.5% and 2%, two sets of shot blasting machines are used, both using cast shot with a diameter of 400-600μm, the shot blasting machine current is set to 100-110A, the frequency is set to 35-40HZ, and the process speed is 25-30m / min; the sulfuric acid pickling concentration is adjusted to 250-280g / l, and the acid temperature is controlled at 78-82℃; the mixed acid pickling nitric acid concentration is 60-70g / l, the hydrofluoric acid concentration is 8-10g / l, and the acid temperature is controlled at 45-50℃.

[0008] Furthermore, in step S4, the rolling rolls are selected from M42 high-speed steel rolls, the rolling speed limit for the first pass is 120-150 m / min, the rolling speed limit for the last pass is 80-120 m / min, and the rolling oil flow rate is controlled at 2500-3500 L / min.

[0009] Further, in step S5, the conductivity of the degreasing section is controlled at 4–8 mS, and the temperature is controlled at 70–75°C; the annealing temperature is controlled at 1020°C–1050°C, the furnace pressure is controlled at 8–12 Pa, the residual oxygen is controlled at 2%–4%, and the TV value is controlled at 110–120 mm·m / min; the pickling current is controlled at 4000–6000 A, the neutral salt concentration is controlled at 180–200 g / L, and the temperature is controlled at 58–62°C; the nitric acid electrolytic pickling current is controlled at 1500–2000 A, the concentration is controlled at 150–180 g / L, and the temperature is controlled at 48–52°C.

[0010] Furthermore, in step S6, the rolling force of the leveling mill is controlled at 1800-2000KN, the tension is controlled at 220-250KN, and the bending force is controlled at 20%-30%.

[0011] Compared with the prior art, the beneficial effects of the present invention are: 1. Low-temperature annealing of black coils can effectively prevent unstable oxidation of the material surface, thereby modifying the surface oxide scale and improving the surface hardness of the material; pre-rolling on a six-roll mill and shot blasting at low speed can effectively reduce the surface roughness of the material.

[0012] 2. The material is pre-rolled using a 20-roll mill to an intermediate thickness. Then, it is pickled with chromium steel wire to further increase the surface corrosion depth. This can effectively treat difficult-to-remove defects such as surface segregation and pits caused by steelmaking continuous casting and hot rolling, resulting in a final mill-rolled raw material with better surface quality.

[0013] 3. The cold treatment line uses low-temperature annealing to reduce the hardness of the final product. At the same time, the pure electrolytic pickling process can avoid severe intergranular corrosion on the surface of austenitic stainless steel, resulting in a brighter material surface after online leveling, which provides a great advantage for reducing costs in subsequent grinding and polishing processes. Attached Figure Description

[0014] Figure 1 The surface microstructure of 2B austenitic stainless steel produced by conventional processes; Figure 2 The microstructure of austenitic stainless steel 2B after treatment by the present invention; Figure 3 The macroscopic morphology of austenitic stainless steel 2B after conventional processing. Figure 4 The image shows the macroscopic morphology of the surface of austenitic stainless steel 2B after treatment by the present invention. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of the invention.

[0016] Example 1 A cold rolling process for high-quality austenitic stainless steel 2B for surface decoration, the specific process includes the following steps: S1. Annealing and Pickling of Hot-Rolled Austenitic Coil: 4.5mm thick austenitic hot-rolled coils are rolled using a six-roll mill with a rolling reduction controlled at 10%. After rolling, annealing is performed using a furnace temperature control mode, with the furnace temperature set at 1020℃ throughout and a TV value of 160mm•m / min. Following annealing, a continuous pickling process of descaling, shot blasting, sulfuric acid pre-pickling, and mixed acid pickling is used. The descaling machine uses an elongation mode, achieving an elongation rate of 1%. Shot blasting uses 0.6mm diameter cast shot, with a blasting speed controlled at 45m / s and a flow rate controlled at 8kg / m³. 2 The two sets of re-brushing phosphorus removal gears for sulfuric acid pre-washing are controlled at level 5. The mixed acid concentration for mixed acid washing is controlled at 120g / l for nitric acid and 25g / l for hydrofluoric acid, and the acid temperature is controlled at 45℃. S2, 20-roll mill pre-rolling: The steel coil after step S1 is pre-rolled to an intermediate thickness of 2.0 mm using a 20-roll mill. M42 high-speed steel rolls are selected. The rolling reduction rate is controlled at 30%. The rolling speed limit for the first pass is 120 m / min, the rolling speed limit for the last pass is 80 m / min, and there is no speed limit for the remaining passes. The rolling oil flow rate is controlled at 2500 L / min to obtain the pre-rolled hardened steel coil. S3. Chromium steel wire pickling treatment: The steel coil treated in step S2 is first degreased and deoiled, and then chromium steel wire surface treatment is performed. The elongation rate of the scale-breaking machine for chromium steel wire surface treatment is set to 1.5%. Two sets of shot blasting machines are used, both with 400μm diameter shot. The shot blasting machine current is set to 100A, the frequency is set to 35HZ, the process speed is 25m / min, the sulfuric acid pickling concentration is adjusted to 250g / l, the acid temperature is controlled at 78℃, the mixed acid pickling nitric acid concentration is 60g / l, the hydrofluoric acid concentration is 8g / l, and the acid temperature is controlled at 45℃. S4, 20-roll mill rolling: The steel coil processed in step S3 is rolled for the final rolling. M42 high-speed steel rolls are used to roll to a final thickness of 0.8mm. The rolling reduction rate is controlled at 25%. The rolling speed limit for the first pass is 120m / min, and the rolling speed limit for the last pass is 80m / min. The rolling oil flow rate is controlled at 2500L / min. S5. Cold Annealing and Pickling Treatment: The hardened steel coil treated in step S4 is first degreased. The conductivity of the degreasing section is controlled at 4 mS, and the temperature is controlled at 70℃. After degreasing, it is annealed. The annealing temperature is controlled at 1020℃, the furnace pressure is controlled at 8 Pa, the residual oxygen is controlled at 2%, and the TV value is controlled at 110 mm·m / min. After annealing, it is subjected to neutral salt electrolytic pickling treatment. The pickling current is controlled at 4000A, the neutral salt concentration is controlled at 180 g / L, and the temperature is controlled at 58℃. The nitric acid electrolytic pickling current is controlled at 1500A, the concentration is controlled at 150 g / L, and the temperature is controlled at 48℃. S6. Online leveling: The steel coil processed in step S5 is leveled. The rolling force of the leveling machine is controlled at 1800KN, the tension is controlled at 220KN, and the bending roll force is controlled at 20%, finally obtaining high-quality decorative austenitic stainless steel 2B surface material. S7, ETD Slitting Processing: The materials produced in the previous process are processed according to customer requirements to determine the length, width, and weight, and then packaged and stored.

[0017] Example 2 A cold rolling process for high-quality austenitic stainless steel 2B for surface decoration, the specific process includes the following steps: S1. Annealing and Pickling of Hot-Rolled Austenitic Coil: 5.0mm thick austenitic hot-rolled coils are rolled using a six-roll mill with a rolling reduction controlled at 13%. After rolling, annealing is performed using a furnace temperature control mode, with the furnace temperature set at 1035℃ throughout and a TV value of 170mm•m / min. Following annealing, a continuous pickling process of descaling, shot blasting, sulfuric acid pre-pickling, and mixed acid pickling is used. The descaling mill uses an elongation mode, achieving an elongation rate of 1.3%. Shot blasting uses 0.7mm diameter cast shot, with a blasting speed controlled at 50m / s and a flow rate controlled at 10kg / m³. 2 The two sets of re-brushing dephosphorization gears for sulfuric acid pre-washing are controlled at level 6. The mixed acid concentration for mixed acid washing is controlled at 125 g / L for nitric acid and 27 g / L for hydrofluoric acid, and the acid temperature is controlled at 48℃. S2, 20-roll pre-rolling: The steel coil processed in step S1 is pre-rolled to an intermediate thickness of 2.8mm using a 20-roll mill. M42 high-speed steel rolls are selected, the rolling reduction rate is controlled at 42%, the rolling speed limit for the first pass is 135m / min, the rolling speed limit for the last pass is 100m / min, and the speed limit for the remaining passes is not limited. The rolling oil flow rate is controlled at 3000L / min to obtain the pre-rolled hardened steel coil. S3. Chromium steel wire pickling treatment: The steel coil treated in step S2 is first degreased and deoiled, and then chromium steel wire surface treatment is performed. The elongation rate of the scale-breaking machine for chromium steel wire surface treatment is set to 1.7%. Two sets of shot blasting machines are used, both with 500μm diameter shot. The shot blasting machine current is set to 105A, the frequency is set to 38HZ, the process speed is 27m / min, the sulfuric acid pickling concentration is adjusted to 265g / l, the acid temperature is controlled at 80℃, the mixed acid pickling nitric acid concentration is 65g / l, the hydrofluoric acid concentration is 9g / l, and the acid temperature is controlled at 48℃. S4, 20-roll mill rolling: The steel coil processed in step S3 is rolled for the final rolling. M42 high-speed steel rolls are used to roll to a final thickness of 1.4mm. The rolling reduction rate is controlled at 42%. The rolling speed limit for the first pass is 135m / min, and the rolling speed limit for the last pass is 100m / min. The rolling oil flow rate is controlled at 3000L / min. S5. Cold Annealing and Pickling Treatment: The hardened steel coil after step S4 is first degreased. The conductivity of the degreasing section is controlled at 6 mS and the temperature is controlled at 72℃. After degreasing, it is annealed. The annealing temperature is controlled at 1035℃, the furnace pressure is controlled at 10 Pa, the residual oxygen is controlled at 3%, and the TV value is controlled at 115 mm·m / min. After annealing, it is subjected to neutral salt electrolytic pickling treatment. The pickling current is controlled at 5000A, the neutral salt concentration is controlled at 190 g / L, and the temperature is controlled at 60℃. The nitric acid electrolytic pickling current is controlled at 1750A, the concentration is controlled at 165 g / L, and the temperature is controlled at 50℃. S6. Online leveling: The steel coil processed in step S5 is leveled. The rolling force of the leveling machine is controlled at 1900KN, the tension is controlled at 235KN, and the bending roll force is controlled at 25%, finally obtaining high-quality decorative austenitic stainless steel 2B surface material. S7, ETD Slitting Processing: The materials produced in the previous process are processed according to customer requirements to determine the length, width, and weight, and then packaged and stored.

[0018] Example 3 S1. Annealing and Pickling of Hot-Rolled Austenitic Coil: 5.5mm thick austenitic hot-rolled coils are rolled using a six-roll mill with a rolling reduction controlled at 15%. After rolling, annealing is performed using a furnace temperature control mode, with the furnace temperature set between 1050℃ and a TV value of 180mm•m / min. Following annealing, a continuous pickling process of descaling, shot blasting, sulfuric acid pre-pickling, and mixed acid pickling is used. The descaling mill uses an elongation mode, achieving an elongation rate of 1.5%. Shot blasting uses 0.8mm diameter cast shot, with a blasting speed controlled at 54m / s and a flow rate controlled at 12kg / m³. 2The two sets of re-brushing dephosphorization gears for sulfuric acid pre-washing are controlled at level 7. The mixed acid concentration for mixed acid washing is controlled at 130 g / L for nitric acid and 30 g / L for hydrofluoric acid, and the acid temperature is controlled at 50℃. S2, 20-roll mill pre-rolling: The steel coil after step S1 is pre-rolled to an intermediate thickness of 3.5mm using a 20-roll mill. M42 high-speed steel rolls are selected. The rolling reduction rate is controlled at 60%. The rolling speed limit for the first pass is 150m / min, the rolling speed limit for the last pass is 120m / min, and there is no speed limit for the remaining passes. The rolling oil flow rate is controlled at 3500L / min to obtain the pre-rolled hardened steel coil. S3. Chromium steel wire pickling treatment: The steel coil treated in step S2 is first degreased and deoiled, and then chromium steel wire surface treatment is performed. The elongation rate of the scale-breaking machine for chromium steel wire surface treatment is set to 2%. Two sets of shot blasting machines are used, both with 600μm diameter shot. The shot blasting machine current is set to 110A, the frequency is set to 40HZ, the process speed is 30m / min, the sulfuric acid pickling concentration is adjusted to 280g / l, the acid temperature is controlled at 82℃, the mixed acid pickling nitric acid concentration is 70g / l, the hydrofluoric acid concentration is 10g / l, and the acid temperature is controlled at 50℃. S4, 20-roll mill rolling: The steel coil processed in step S3 is rolled for the final rolling. M42 high-speed steel rolls are used to roll to a final thickness of 2.0mm. The rolling reduction rate is controlled at 60%. The rolling speed limit for the first pass is 150m / min, and the rolling speed limit for the last pass is 120m / min. The rolling oil flow rate is controlled at 3500L / min. S5. Cold Annealing and Pickling Treatment: The hardened steel coil treated in step S4 is first degreased. The conductivity of the degreasing section is controlled at 8 mS, and the temperature is controlled at 75℃. After degreasing, annealing is performed. The annealing temperature is controlled at 1050℃, the furnace pressure is controlled at 12 Pa, the residual oxygen is controlled at 4%, and the TV value is controlled at 120 mm·m / min. After annealing, neutral salt electrolytic pickling treatment is performed. The pickling current is controlled at 6000 A, the neutral salt concentration is controlled at 200 g / L, and the temperature is controlled at 62℃. Nitric acid electrolytic pickling current is controlled at 2000 A, the concentration is controlled at 180 g / L, and the temperature is controlled at 52℃. S6. Online leveling: The steel coil processed in step S5 is leveled. The rolling force of the leveling machine is controlled at 2000KN, the tension is controlled at 250KN, and the bending roll force is controlled at 30%, finally obtaining high-quality decorative austenitic stainless steel 2B surface material. S7, ETD Slitting Processing: The materials produced in the previous process are processed according to customer requirements to determine the length, width, and weight, and then packaged and stored.

[0019] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A cold rolling process for high-quality austenitic stainless steel 2B for surface decoration, characterized in that: Includes the following steps: S1. Annealing and pickling of hot-rolled austenitic black coils with a thickness of 4.5-5.5mm: six-roll mill rolling is performed, with the rolling reduction rate controlled between 10% and 15%. After rolling, annealing is performed, and after annealing, a continuous pickling process of descaling-shot blasting-sulfuric acid pre-pickling-mixed acid pickling is used for pickling. S2, 20-roll mill pre-rolling: The thickness of the steel coil processed in step S1 is pre-rolled to an intermediate thickness of 2.0mm to 3.5mm using a 20-roll mill, and the rolling reduction rate is controlled at 25% to 60% to obtain a pre-rolled hardened steel coil. S3. Chromium steel wire pickling treatment: The steel coil treated in step S2 is first degreased and deoiled, and then chromium steel wire surface treatment is performed. The elongation of the scale-breaking machine for chromium steel wire surface treatment is set between 1.5% and 2%. Two sets of shot blasting machines are used, both with shot diameter of 400-600μm. The shot blasting machine current is set to 100-110A, the frequency is set to 35-40HZ, and the process speed is 25-30m / min. The sulfuric acid pickling concentration is adjusted to 250-280g / l, and the acid temperature is controlled at 78-82℃. The mixed acid pickling has a nitric acid concentration of 60-70g / l, a hydrofluoric acid concentration of 8-10g / l, and an acid temperature controlled at 45-50℃. S4, 20-roll mill rolling: The steel coil processed in step S3 is rolled to a final thickness of 0.8mm to 2.0mm, with the rolling reduction rate controlled at 25% to 60%; S5. Cold annealing and pickling treatment: The rolled hardened steel coil after step S4 is first degreased, then annealed, and then subjected to neutral salt electrolytic pickling treatment. S6. Online leveling: The steel coil processed in step S5 is leveled to obtain high-quality decorative austenitic stainless steel 2B surface material. S7, ETD Slitting Processing: The materials produced in the previous process are processed according to customer requirements to determine the length, width, and weight, and then packaged and stored.

2. The cold rolling process for high-quality surface-decorated austenitic stainless steel 2B material according to claim 1, characterized in that: In step S1, the annealing process adopts a furnace temperature control mode, with the furnace temperature set between 1020℃ and 1050℃ throughout the process, and a TV value of 160 to 180 mm•m / min. In the continuous pickling process, the scale-breaking machine adopts an extension mode, with an elongation rate of 1% to 1.5%. Shot blasting uses full-cast shot with a diameter of 0.5 to 0.8 mm, with the blasting speed controlled at 45 to 54 m / s and the flow rate controlled at 8 to 12 kg / m³. 2 The phosphorus removal speed of the two sets of sulfuric acid pre-washing brushes is controlled at level 5 to 7; the mixed acid concentration of the mixed acid wash is controlled at 120 to 130 g / L for nitric acid and 25 to 30 g / L for hydrofluoric acid, and the acid temperature is controlled at 45 to 50℃.

3. The cold rolling process for high-quality surface-decorated austenitic stainless steel 2B material according to claim 2, characterized in that: In step S2, the rolling rolls are M42 high-speed steel rolls. The rolling speed is limited to 120-150 m / min for the first pass and 80-120 m / min for the last pass. There is no speed limit for the remaining passes. The rolling oil flow rate is controlled at 2500-3500 L / min.

4. The cold rolling process for high-quality surface-decorated austenitic stainless steel 2B material according to claim 3, characterized in that: In step S4, the rolling rolls are M42 high-speed steel rolls. The rolling speed is limited to 120-150 m / min for the first pass and 80-120 m / min for the last pass. The rolling oil flow rate is controlled at 2500-3500 L / min.

5. The cold rolling process for high-quality surface-decorated austenitic stainless steel 2B material according to claim 4, characterized in that: In step S5, the conductivity of the degreasing section is controlled at 4–8 mS, and the temperature is controlled at 70–75°C. The annealing temperature is controlled at 1020°C–1050°C, the furnace pressure at 8–12 Pa, the residual oxygen at 2%–4%, and the TV value at 110–120 mm·m / min. The pickling current is controlled at 4000–6000 A, the neutral salt concentration at 180–200 g / L, and the temperature at 58–62°C. The nitric acid electrolytic pickling current is controlled at 1500–2000 A, the concentration at 150–180 g / L, and the temperature at 48–52°C.

6. The cold rolling process for high-quality surface-decorated austenitic stainless steel 2B material according to claim 5, characterized in that: In step S6, the leveling process is carried out by a leveling machine, wherein the rolling force of the leveling machine is controlled at 1800-2000KN, the tension is controlled at 220-250KN, and the bending force is controlled at 20%-30%.

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