A solution to the sticking mark defect of thin gauge 316 stainless steel during finish rolling

Abstract

The present application relates to the cold rolling production process of the precision strip steel product SUS316L of the precision strip company, mainly the thin specification system stainless steel cold plate rolling, annealing process technology of 0.6mm <= thickness <= 1.2mm, a kind of solution to the defect of 316 system stainless steel thin specification sticking roll printing when finish rolling.It can eliminate the scheme of the production speed control of finished product pickling according to surface condition is not clear, the deformation of rolling pass, the improper selection of plate shape target curve, the problem of transition passivation caused by finished product pickling, surface defect caused by final finish rolling, thoroughly solve the defect of 316 system precision strip steel product finish rolling sticking roll printing, improve production efficiency, reduce manufacturing cost.It is characterized in that: it includes the following methods: (1) rolling deformation control scheme; (2) cold line process optimization; (3) bright line production scheme; (4) finish rolling control scheme.

Description

TECHNICAL FIELD

[0001] The present application relates to the cold rolling production process of the precision strip steel product SUS316L of the precision strip company, mainly the annealing process technology of the thin specification system stainless steel cold plate 0.6mm<=thickness<=1.2mm, and particularly relates to a solution method for solving the roll sticking and printing defects of the thin specification 316 system stainless steel during finish rolling. BACKGROUND

[0002] SUS316L is a high-end precision strip steel product developed by TISCO, which has the characteristics of good elasticity, good forming property and high fatigue strength. It is applied in the fields of aerospace and new energy. The product surface is required to be strict, and the product precision is required to be high. The thickness of the finished product is 0.02-0.2mm. Typical applications: honeycomb structure material, elastic sensitive element, heat insulation part, corrugated pipe, metal diaphragm and all metal parts in contact with diaphragm pressure medium, helicopter connecting shaft device, lining, clamp, spring and various components, hydrogen fuel cell, etching processing, electrode reactor base material.

[0003] The strict surface requirement and high precision requirement cause great difficulty in production. The surface transition pickling and passivation defects and the roll sticking and printing defects of the finish rolling surface in the production process will cause low qualified rate, and the production cost will be greatly increased. Therefore, a method for quickly and effectively solving the problem is urgently needed.

[0004] In view of the above problems, the present application provides a roll sticking and printing defect solution method for thin specification 316 system stainless steel finish rolling, which can quickly and effectively improve the quality control level of thin specification 316 system cold plate finish rolling. SUMMARY

[0005] The purpose of the present application is to provide a solution method for solving the roll sticking and printing defects of thin specification 316 system stainless steel finish rolling.

[0006] The objective of this invention is achieved as follows: a solution to the roller mark defect during the precision rolling of thin-gauge 316 series stainless steel, comprising the following steps: Step 1: Rolling process: The deformation amount of the first pass in the first rolling stroke is adjusted to below 25%, gradually decreasing to 60% of the total deformation amount of the finished product passes; Step 2: Pickling is performed at the end of the first rolling stroke, with a pickling speed of 25-60 mpm, annealing temperature of 1100±℃, first performing electrolytic sodium sulfate pickling, with a sodium sulfate concentration of 1.1-1.2 g / m³, iron ions ≤60 g / l, acid temperature of 80-90℃, followed by mixed acid pickling. The acid is a mixture of nitric acid and hydrofluoric acid, with a nitric acid concentration of 120-180 g / L and a hydrofluoric acid concentration of 20±5 g / L. The acid temperature is 45-55℃. Step 3: After pickling, the second rolling process is carried out. The deformation of the first pass of the second rolling process is capped at 20%, gradually decreasing to the target thickness. Step 4: After the second rolling process, bright furnace annealing is carried out. The furnace temperature is required to be 1160℃, the hydrogen content is controlled at 85-90%, the degreasing conductivity is 10-15 g / m³, and the cleaning section is put into full re-brushing. The speed of the brushing machine is 700 rpm, and the TV value is 30. Step 5: After the bright furnace annealing, the finishing rolling process is carried out.

[0007] Step five, the finishing rolling process, specifically involves setting the target shape curves for the first and second passes to be convex curves on both sides, with the edge shape value set at 10~30 N / mm. 2 As the number of passes increases, the edge shape value also increases. For the third pass before the finished product, a straight curve is selected as the target shape curve, and the edge shape value is set to 10 N / mm. 2 The target curve for the finished product pass is selected as a concave curve on both sides, with the edge shape value set to -10 to -20 N / mm. 2 As the number of passes increases, the edge shape value decreases accordingly, and the passes before and after the finished product are rolled with flat rolls.

[0008] The beneficial effects of this invention are: 1. By standardizing the rolling process and the deformation amount of each pass, it is possible to ensure that the rolling pressure distribution of each pass is reasonable, the rolling process and the target curve of the plate shape are matched, and the plate shape after each pass is straight, so as not to cause damage to the steel coil base due to excessive rolling deformation.

[0009] 2. By optimizing the process and standardizing the speed of finished product annealing and pickling, the problem of excessive acidification of steel strip can be improved, and product production efficiency can be increased.

[0010] 3. By adjusting the production process, the problem of excessive pickling and passivation of steel strip can be improved, achieving the annealing requirements while degreasing and brushing ensure the surface purity. This enhances the surface finish of the next finishing rolling step.

[0011] 4. By implementing a shape control scheme for different finishing passes, the shape of SUS316L products can be improved, thereby eliminating the leveling process, reducing manufacturing costs, optimizing processes and operations, clarifying the key points for shape defect control in different passes, ensuring that the finished product has a straight shape after each pass and does not produce surface defects such as roller marks. This invention reduces the scrap rate due to roller marks during finishing rolling and is highly operable.

[0012] By adopting the method of this invention, the problem of roller marks during the fine rolling of thin 316 series precision strip steel has been successfully solved, and the surface qualification rate has been increased from 90% to over 99%. Attached Figure Description

[0013] The present invention will now be further described with reference to the accompanying drawings.

[0014] Figure 1 This is a target profile curve diagram of the first and second passes of the thin-gauge 316 series precision strip rolling of the present invention.

[0015] Figure 2 This is the target shape curve diagram of the third to the finished product stage of the thin-gauge 316 series precision strip rolling process of the present invention.

[0016] Figure 3 This is a target curve diagram of the finished strip shape of the thin-gauge 316 series precision strip steel in the precision rolling process of this invention. Implementation

[0017] Through on-site testing, it was verified that the cause of the sticky roller marks during finishing rolling was unclear pickling process and production speed during the finished product annealing and pickling process to ensure the required pickling surface. Furthermore, the deformation amount for each pass in the rolling process was improperly selected, resulting in imperfect cleaning and excessive acid passivation of the steel strip surface, leading to the sticky roller marks defect. This invention improves the finishing rolling roller marks defect by optimizing the rolling and pickling processes, formulating a bright line production plan, and optimizing the finishing rolling process. This improves production efficiency and reduces manufacturing costs.

[0018] Based on the causes of this problem, a method for improving the surface of thin-gauge 316 series precision strip steel is proposed. This method involves four aspects: adjustment of rolling deformation, optimization of finished product pickling process, adjustment of production process, and optimization of finishing rolling process. It is systematic and practical. The specific method is as follows.

[0019] (1) Adjustment of rolling deformation

[0020] The pickling and annealing process for SUS316L raw materials involves a plate temperature of 1100±10℃ and a TV value of 100 (TV value is a stainless steel strip processing capacity indicator; T represents the thickness of the stainless steel strip, and V represents the operating speed; TV value is the product of the two, measured in mm*m / min). The hot-rolled grain size is controlled at grade 7.5±0.5. The pickling process requires a nitric acid concentration of 120-180 g / L, an acid temperature of 80-90℃, hydrofluoric acid of 20±5 g / L, and a temperature of 45-55℃, with iron ions ≤60 g / L. This ensures the steel plate is thoroughly cleaned of iron and phosphorus, with no under- or over-acidification. Subsequent rolling process requirements are as follows:

[0021] Taking SUS316L with a feed thickness of 3.0mm and a finished product thickness of 0.7mm as an example, the deformation amount of the first pass in the first rolling process is adjusted from the upper limit of 30% to below 25%, and gradually reduced to 60% of the total deformation amount of the finished product passes, controlling the plate shape and edge waviness, as shown in Table 1. The upper limit of the deformation amount of the first pass in the second rolling process is 20%, and it is gradually reduced to the target thickness, as shown in Table 2.

[0022]

[0023] (2) Cold line pickling process

[0024] SUS316L grade steel should be pickled according to the 316L process conditions to ensure the acid concentration requirements. It is forbidden to reduce the production speed to ensure the pickling effect. Avoid over-pickling of the steel coil surface. The surface darkening has been tested and can be improved in the second rolling and second annealing. The minimum production speed is 25mpm, as shown in Table 3.

[0025]

[0026] (3) Adjustment of production process

[0027] The production process for SUS316L steel is as follows: raw material annealing and pickling, first rolling stroke, finished product annealing and pickling, second rolling stroke, and finished product annealing and pickling. Tests have shown that this production process is prone to over-pickling during the second finished product annealing and pickling, resulting in excessive passivation of the steel coil surface. This, in turn, causes roller marks during the subsequent finishing rolling process.

[0028] Adjust the process route, and after the second rolling process, anneal in a bright furnace with a furnace temperature of 1160℃, hydrogen content of more than 85%, and degreasing conductivity of 10-15. Put the cleaning section into use for full re-brushing with a TV value of 30, as shown in Table 4.

[0029]

[0030] (4) Optimization of finishing rolling process

[0031] Selection of target shape curves for the first and second passes during the finishing rolling process Figure 1 The edge plate stress deviation value is taken as 10~30N / mm.2 Selection of target curve for plate shape in the second to final product stages. Figure 2 Selection of target curve for finished product pass shape Figure 3 The edge plate stress deviation value is taken as -10~-20N / mm. 2 The deformation amount is capped at 20% for the first pass, decreasing progressively. Flat rolls are used for both the passes before and after the finished product. Example 1

[0032] The cold rolling process produces a 0.7*1219mm SUS316L precision strip. First, the raw material undergoes annealing and pickling at a plate temperature of 1133℃, a speed of 32mpm, a nitric acid concentration of 170g / l, a hydrofluoric acid concentration of 23g / l, and an acid temperature of 44℃. The pickling effect on the steel plate is good. The first rolling pass is set with a first-pass deformation of 25% and a unit tension of 170 N / mm. 2 75 N / mm 2 The deformation amounts in subsequent passes were 13.2%, 12.78%, and 9.53%, respectively. The raw material thickness was 2.92 mm, and 1.5 mm after the first rolling pass. The maximum speed for the first rolling pass before the finished product was 200 m / min, and the maximum speed for the finished product pass was 150 m / min. The rolling oil flow rate was 11,000 l / min at full flow.

[0033] The first pickling of the finished product was performed at a plate temperature of 1103℃, a speed of 28mpm, a nitric acid concentration of 180g / l, and a hydrofluoric acid concentration of 21.3g / l. The pickled surface was slightly dull, but the surface was acceptable.

[0034] In the second rolling pass, the diameter is rolled from 1.5mm to 0.7mm, with a first-pass deformation of 20% and a unit tension of 166 N / mm. 2 72N / mm 2 The deformation amounts in subsequent passes were 16.83%, 14.82%, 13.8%, and 11.2%, respectively. The final thickness was 0.65 mm, achieving the target thickness. No backing paper was used in the second rolling pass, and the edge drop of the finished product's shape defect was controlled at -20 N / mm. 2 The steel strip has slight edge waviness. During bright production, the edge stress is released, resulting in a straight strip shape, which facilitates subsequent rolling processes.

[0035] The final annealing, pickling, and brightening furnace in Zone 8 was put into operation with a furnace temperature of 1158℃, TV value of 29, hydrogen content of 85%, degreasing conductivity of 14g / m³, and re-brushing speed of 700 rpm.

[0036] Selection of target plate shape curves for the first and second passes of finishing rolling Figure 1 The edge plate stress deviation is 15 N / mm. 2 Selection of target curve for plate shape in the second to final product stages. Figure 2 Selection of target curve for finished product pass shape Figure 3The edge plate stress deviation value is taken as -17N / mm. 2 The deformation amount is set at 18% for the first pass, and the edge plate stress deviation is set at 20 N / mm. 2 The deformation of the finished product is 6%. After running at low speed for 100 meters and checking for no surface defects, it is rolled normally.

[0037] The above description is only a specific embodiment of the present invention, but the structural features protected by the present invention are not limited thereto. Any changes or modifications made by those skilled in the art within the scope of the present invention are covered by the patent scope of the present invention.

Claims

1. A solution to the roller mark defect during the precision rolling of thin-gauge 316 series stainless steel, characterized in that: Includes the following steps: Step 1: Rolling process: The deformation amount of the first pass in the first rolling stroke is adjusted to below 25%, and gradually reduced to 60% of the total deformation amount of the finished product passes; Step 2: Pickling is performed after the first rolling pass. The pickling speed is 25-60 mpm, and the annealing plate temperature is 1100±℃. Electrolytic sodium sulfate pickling is performed first, with a sodium sulfate concentration of 1.1-1.2 g / m³, iron ion concentration ≤60 g / l, and acid temperature of 80-90℃. Then, mixed acid pickling is performed, which is a mixture of nitric acid and hydrofluoric acid. The nitric acid concentration is 120-180 g / l, the hydrofluoric acid concentration is 20±5 g / l, and the acid temperature is 45-55℃. Step 3: After pickling, proceed with the second rolling pass. The maximum deformation amount in the first pass of the second rolling pass is 20%, which is gradually reduced to the target thickness. Step 4: After the second rolling pass, bright furnace annealing is carried out. The furnace temperature is required to be 1160℃, the hydrogen content is controlled at 85-90%, and the degreasing conductivity is 10-15g / m³. The cleaning section is put into use for full re-brushing. The speed of the brushing machine is 700 rpm, and the TV value is 30. The TV value is the stainless steel strip processing capacity index value. T represents the thickness of the stainless steel strip, and V represents the operating speed. The TV value is the product of the two, and the unit is mm*m / min. Step 5: After bright furnace annealing, proceed with the precision rolling process; Step five, the finishing rolling process, specifically involves setting the target shape curves for the first and second passes to be convex curves on both sides, with the edge shape value set at 10~30 N / mm. 2 As the number of passes increases, the edge shape value also increases. For the third pass before the finished product, a straight curve is selected as the target shape curve, and the edge shape value is set to 10 N / mm. 2 The target curve for the finished product pass is selected as a concave curve on both sides, with the edge shape value set to -10 to -20 N / mm. 2 As the number of passes increases, the edge shape value decreases accordingly, and the passes before and after the finished product are rolled with flat rolls.

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