2D surface control method for SUS410L stainless steel for refrigerated container meeting ink test

Abstract

The application discloses a 2D surface control method for SUS410L stainless steel for refrigerated containers meeting ink test, and mainly comprises the following technical contents: (1) roughness control of No. 1 plate of a hot rolling annealing pickling line; (2) surface quality requirement of working rolls of a 20-roll mill; (3) influence of degreasing and pickling concentration of a cold rolling annealing pickling line on surface tension and roughness; and (4) cleaning of a tension leveler set to further increase the surface tension of 2D material. The application controls the roughness and surface tension of the 2D surface by controlling the pickling concentration of hot / cold lines, the roll surface and degreasing and cleaning, so as to meet the ink test of the 38# or above grade, and thus the material surface has stable and uniform paint spraying effect.

Description

Technical Field

[0001] This invention belongs to the field of stainless steel rolling and pickling technology, and specifically relates to a 2D surface control method for SUS410L stainless steel used in refrigerated containers to meet ink testing requirements. Background Technology

[0002] SUS410L ferritic stainless steel has strictly controlled content of harmful elements P and S, possesses excellent corrosion resistance, and has stringent sheet shape requirements. It is mainly used in the manufacture of high-end refrigerated containers. No.1 sheet is primarily processed into supporting structures such as frames and ladders; 2D sheet, due to its higher elongation and better sheet shape (wave height < 5mm), is mainly used as raw material for processing the exterior panels of containers. The panel painting process in refrigerated container manufacturing provides aesthetically pleasing colors and gloss, avoiding damage from environmental and chemical corrosion; paints typically use components such as polyurethane, acrylic, and epoxy resins.

[0003] To achieve good painting results, SUS410L stainless steel 2D sheets must pass an ink test of grade 38 or higher. The specific test method is as follows: Draw a 2mm wide ink test strip at least 10mm long on an uncontaminated steel sheet. If the ink does not shrink or break within 2 seconds, it indicates that the surface roughness and surface tension of the steel are sufficient to ensure good painting results during subsequent processing.

[0004] Currently, the surface roughness and surface tension of ordinary stainless steel production methods cannot meet the requirements of ink testing. This invention focuses on controlling the surface roughness and surface tension of SUS410L stainless steel strip to ensure that SUS410L stainless steel 2D sheets used in refrigerated containers pass ink testing of grade 38 or higher. Summary of the Invention

[0005] The purpose of this invention is to provide a 2D surface control method for SUS410L stainless steel used in refrigerated containers to meet ink testing standards. This method controls the surface roughness and surface tension of SUS410L stainless steel strips to ensure that SUS410L stainless steel 2D sheets used in refrigerated containers pass ink testing of grade 38 or higher.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A 2D surface control method for SUS410L stainless steel used in refrigerated containers that meets ink testing standards includes the following steps: Step 1, Hot Rolling Annealing and Pickling Line: Annealing and pickling SUS410L black coils to obtain No.1 plates with a surface roughness of 2.0-3.0μm; Step 2, 20-roll mill rolling: The No.1 plate from Step 1 is rolled to obtain a hardened steel coil. The rolling passes are 5 to 7 times to achieve the desired thickness. The work rolls follow the F+G system. The roughing passes use F rolls with a roughness Ra controlled at 0.8 to 1.5 μm. The finishing passes use G rolls with a roughness Ra controlled at 0.20 to 0.35 μm.

[0007] Step 3, Cold Rolling Annealing and Pickling Line: Annealing and pickling hardened steel coils to produce 2D surface SUS410L steel coils with a roughness of 0.25-0.35. The annealing temperature is 780~850℃, the electrical conductivity of the degreasing section is 9±3ms, and the temperature is 70~75℃. The pickling section uses neutral salt electrolysis, nitric acid electrolysis, and mixed acid pickling. The neutral salt electrolysis current is 3000~4000A, the nitric acid electrolysis current is 2000~3000A, and the concentrations of hydrofluoric acid and nitric acid in the mixed acid pickling are 15-20 and 80-100g / L, respectively, and the temperature is 45-55℃. The annealing pickling speed is 40~60m / min.

[0008] Step 4, Straightening Unit: Clean the 2D surface of the steel coil again to control surface oil and other defects, reduce the surface tension of the strip, and pass the ink test of grade 38 or above. The hot water temperature of the spray beam in the cleaning section of the straightening unit is set to 70~80℃, and the steam temperature in the drying section is set to 80~90℃.

[0009] Preferably, the annealing temperature in step 1 is 800~880℃; the sulfuric acid pickling concentration in the pre-pickled section is 350±20g / L, and the temperature is 70-80℃; the concentration ratio in the mixed acid pickling is: nitric acid pickling 50-70g / L, hydrofluoric acid 10-20g / L, and the temperature is 40-50℃; the annealing pickling speed is 20~35m / min.

[0010] The beneficial effects of this invention are as follows: This invention controls the surface roughness of the No.1 sheet in the hot-rolled annealing and pickling line, and then uses the surface quality requirements of the work rolls of the 20-roll mill. Based on the influence of degreasing and pickling concentration on surface tension and surface roughness in the cold-rolled annealing and pickling line, the surface tension of the 2D material is further increased by using the cleaning of the tension leveling unit. Through the above methods, oil stain defects on the surface of the 2D material are controlled, the surface tension of the strip is reduced, and the material can pass the ink test of grade 38# or higher. Attached Figure Description

[0011] Figure 1 Photo of a SUS410L stainless steel 2D sheet that failed the ink test. Figure 2 Photographs showing the ink test results of the SUS410L stainless steel 2D sheet produced by this invention. Figure 3The outer panel of the refrigerated container is made of SUS410L stainless steel produced for this invention. Detailed Implementation

[0012] The present invention will be further described in detail with reference to the following specific embodiments.

[0013] Implementation Method 1 (1) Hot-rolled annealing and pickling line: SUS410L ferritic stainless steel hot-rolled black coils are annealed and pickled to produce No.1 plates with a thickness of 5.0 mm and a surface roughness of 2.50 μm. Annealing temperature is 810℃; the sulfuric acid pickling concentration in the pre-pickling section is 340 g / L and the temperature is 70℃; the mixed acid pickling is nitric acid pickling of 70 g / L + hydrofluoric acid of 10 g / L and the temperature is 45℃; the annealing pickling speed is 35 m / min.

[0014] (2) Twenty-roll mill rolling: The No.1 plate base material from step 1 is rolled in 5 passes to form a hardened steel coil with a thickness of 1.20 mm; the roughness Ra of the work roll F roll in the roughing pass is 1.0 μm, and the roughness Ra of the finish rolling pass G roll is controlled at 0.25 μm.

[0015] (3) Cold rolling annealing and pickling line: The hardened steel coils from step 2 are annealed and pickled to obtain SUS410L steel coils with a 2D surface and a roughness of 0.28μm. The annealing temperature is 800℃, the conductivity of the degreasing section is 7ms and the temperature is 70℃; the pickling section uses neutral salt + nitric acid electrolysis with currents of 3200A + 2500A, temperatures of 40℃ and 50℃, and concentrations of 170g / L and 160g / L, respectively. The concentrations of hydrofluoric acid and nitric acid in the mixed acid pickling are 17g / L and 80g / L, respectively, and the temperature is 45℃; the annealing and pickling speed is 60m / min.

[0016] (4) Straightening unit: Clean the 2D surface of the steel coil, set the hot water temperature to 70℃, and set the steam temperature of the drying section to 80℃.

[0017] Implementation Method 2 (1) Hot-rolled annealing and pickling line: SUS410L ferritic stainless steel hot-rolled black coils are annealed and pickled to produce No.1 plates with a thickness of 3.0 mm and a surface roughness of 2.10 μm. Annealing temperature is 860℃; sulfuric acid pickling concentration in the pre-pickling section is 360 g / L and temperature is 80℃; mixed acid pickling is nitric acid pickling of 60 g / L + hydrofluoric acid of 15 g / L and temperature is 40℃; annealing and pickling speed is 25 m / min.

[0018] (2) Rolling with a 20-roll mill: The No.1 plate base material of rolling step 1 is rolled into a hardened steel coil with a finished thickness of 0.80mm in 7 passes; the roughness Ra of the F roll in the roughing pass of the work roll is 1.5μm, and the roughness Ra of the G roll in the finishing pass is controlled at 0.30μm.

[0019] (3) Cold rolling annealing and pickling line: The hardened steel coils from step 2 are annealed and pickled to obtain SUS410L steel coils with a 2D surface and a roughness of 0.30μm. The annealing temperature is 825℃, the conductivity of the intermediate degreasing section is 10ms, and the temperature is 75℃; the pickling section uses neutral salt + nitric acid electrolysis with currents of 3500A + 2500A, temperatures of 45℃ and 55℃, and concentrations of 150g / L and 165g / L, respectively. The concentrations of hydrofluoric acid and nitric acid in the mixed acid pickling are 20g / L and 90g / L, respectively, and the temperature is 45℃; the annealing and pickling speed is 45m / min.

[0020] (4) Straightening unit: Clean the 2D surface of the steel coil, set the hot water temperature to 75℃, and set the steam temperature of the drying section to 90℃.

[0021] Implementation Method 3 (1) Hot-rolled annealing and pickling line: SUS410L ferritic stainless steel hot-rolled black coils are annealed and pickled to produce No.1 plates with a thickness of 4.0 mm and a surface roughness of 2.3 μm. Annealing temperature is 830℃; sulfuric acid pickling concentration in the pre-pickling section is 330 g / L and temperature is 75℃; mixed acid pickling is nitric acid pickling of 50 g / L + hydrofluoric acid of 20 g / L and temperature is 50℃; annealing and pickling speed is 30 m / min.

[0022] (2) Twenty-roll mill rolling: The No.1 plate base material from step 1 is rolled in 5 passes to form a hardened steel coil with a thickness of 1.00 mm; the roughness Ra of the work roll F roll in the roughing pass is 0.8 μm, and the roughness Ra of the finish rolling pass G roll is controlled at 0.35 μm.

[0023] (3) Cold rolling annealing and pickling line: The hardened steel coils from step 2 are annealed and pickled to obtain SUS410L steel coils with a 2D surface and a roughness of 0.35μm. The annealing temperature is 850℃, the conductivity of the degreasing section is 11ms and the temperature is 70℃; the pickling section uses neutral salt + nitric acid electrolysis with currents of 3700A + 2600A, temperatures of 45℃ and 55℃, and concentrations of 140g / L and 150g / L, respectively. The concentrations of hydrofluoric acid and nitric acid in the mixed acid pickling are 15 and 100g / L, respectively, and the temperature is 50℃; the annealing and pickling speed is 50m / min.

[0024] (4) Straightening unit: Clean the 2D surface of the steel coil, set the hot water temperature to 80℃, and set the steam temperature of the drying section to 90℃.

[0025] Implementation Method 4 (1) Hot-rolled annealing and pickling line: SUS410L ferritic stainless steel hot-rolled black coils are annealed and pickled to produce No.1 plates with a thickness of 3.5mm and a surface roughness of 2μm. Annealing temperature is 800℃; the sulfuric acid pickling concentration in the pre-pickling section is 330g / L and the temperature is 70℃; the mixed acid pickling is nitric acid pickling of 50g / L + hydrofluoric acid of 10g / L and the temperature is 40℃; the annealing and pickling speed is 20m / min.

[0026] (2) Twenty-roll mill rolling: The No.1 plate base material from step 1 is rolled in 5 passes to form a hardened steel coil with a thickness of 1.00 mm; the roughness Ra of the work roll F roll in the roughing pass is 0.8 μm, and the roughness Ra of the finish rolling pass G roll is controlled at 0.20 μm.

[0027] (3) Cold rolling annealing and pickling line: The hardened steel coils from step 2 are annealed and pickled to obtain SUS410L steel coils with a 2D surface and a roughness of 0.25μm. The annealing temperature is 780℃, the conductivity of the degreasing section is 6ms and the temperature is 70℃; the pickling section uses neutral salt + nitric acid electrolysis with currents of 3000A + 2000A, temperatures of 40℃ and 50℃, and concentrations of 140g / L and 150g / L, respectively. The concentrations of hydrofluoric acid and nitric acid in the mixed acid pickling are 15 and 100g / L, respectively, and the temperature is 50℃; the annealing and pickling speed is 40m / min.

[0028] (4) Straightening unit: Clean the 2D surface of the steel coil, set the hot water temperature to 70℃, and set the steam temperature of the drying section to 80℃.

[0029] Implementation Method 5 (1) Hot-rolled annealing and pickling line: SUS410L ferritic stainless steel hot-rolled black coils are annealed and pickled to produce No.1 plates with a thickness of 4.0 mm and a surface roughness of 3.0 μm. Annealing temperature is 880℃; sulfuric acid pickling concentration in the pre-pickling section is 370 g / L and temperature is 80℃; mixed acid pickling is nitric acid pickling of 70 g / L + hydrofluoric acid of 20 g / L and temperature is 50℃; annealing and pickling speed is 35 m / min.

[0030] (2) Twenty-roll mill rolling: The No.1 plate base material from step 1 is rolled in 5 passes to form a hardened steel coil with a thickness of 1.00 mm; the roughness Ra of the work roll F roll in the roughing pass is 1.5 μm, and the roughness Ra of the finish rolling pass G roll is controlled at 0.35 μm.

[0031] (3) Cold rolling annealing and pickling line: The hardened steel coils from step 2 are annealed and pickled to obtain SUS410L steel coils with a 2D surface and a roughness of 0.35μm. The annealing temperature is 850℃, the conductivity of the degreasing section is 12ms and the temperature is 75℃; the pickling section uses neutral salt + nitric acid electrolysis with currents of 4000A + 3000A, temperatures of 55℃ and 55℃ respectively, and concentrations of 150g / L and 170g / L respectively. The concentrations of hydrofluoric acid and nitric acid in the mixed acid pickling are 20 and 100g / L respectively, and the temperature is 55℃; the annealing and pickling speed is 60m / min.

[0032] (4) Straightening unit: Clean the 2D surface of the steel coil, set the hot water temperature to 80℃, and set the steam temperature of the drying section to 90℃.

Claims

1. A 2D surface control method for SUS410L stainless steel used in refrigerated containers to meet ink testing standards, characterized in that... Includes the following steps: Step 1, Hot Rolling Annealing and Pickling Line: Annealing and pickling SUS410L black coils to obtain No.1 plates with a surface roughness of 2.0-3.0μm. Pickling includes pre-pickling and mixed acid pickling. Step 2, 20-roll rolling: The No.1 plate from Step 1 is rolled to obtain a hardened steel coil. The rolling passes are 5 to 7 times to achieve the desired thickness. The work rolls follow the F+G system. The roughing passes use F rolls with a surface roughness Ra controlled at 0.8 to 1.5 μm, and the finishing passes use G rolls with a surface roughness Ra controlled at 0.20 to 0.35 μm. Step 3, Cold Rolling Annealing and Pickling Line: Annealing and pickling hardened steel coils to produce 2D surface SUS410L steel coils with a roughness of 0.25-0.35μm. The annealing temperature is 780~850℃, and the degreasing section temperature is 70~75℃. The pickling section uses neutral salt electrolysis, nitric acid electrolysis, and mixed acid pickling. The neutral salt electrolysis current is 3000~4000A, the nitric acid electrolysis current is 2000~3000A, and the concentrations of hydrofluoric acid and nitric acid in the mixed acid pickling are 15-20 and 80-100g / L, respectively, at a temperature of 45-55℃. The annealing pickling speed is 40~60m / min. Step 4, Straightening Unit: The steel coil with 2D surface is cleaned again to control surface oil defects, reduce the surface tension of the strip, and pass the ink test of grade 38 or above. The hot water temperature of the spray beam in the cleaning section of the straightening unit is set to 70~80℃, and the steam temperature in the drying section is set to 80~90℃. Passing the ink test of grade 38 or above means that an ink test strip with a width of 2mm and a length of more than 10mm is drawn on the strip, and the ink does not shrink and break within 2 seconds.

2. The 2D surface control method for SUS410L stainless steel used in refrigerated containers conforming to ink testing according to claim 1, characterized in that: In step one, the annealing temperature is 800~880℃; the sulfuric acid pickling concentration in the pre-pickled section is 350±20g / L, and the temperature is 70-80℃; the concentration ratio in the mixed acid pickling is: nitric acid concentration 50-70g / L, hydrofluoric acid concentration 10-20g / L, and the temperature is 40-50℃; the annealing pickling speed is 20~35m / min.

Images