Rolling method for preventing brittle failure of S44626

Abstract

The invention relates to the field of rolling of ultra-pure ferritic stainless steel. A rolling method for preventing brittle failure of S44626 is characterized in that during twenty-roller cold rolling, brittle failure during rolling of the S44626 is prevented by cooperatively adjusting four aspects of rolling deformation, rolling mill tension, a plate shape target curve and roller roughness; according to the rolling deformation, the total rolling deformation is controlled to range from 55% to 65%, constant-deformation rolling is adopted during rolling of the first pass, the second pass, the third pass and the third pass, and the deformation ranges from 12.5% to 14.5%; when the tension of the rolling mill is set, the front unit tension is 65 N / mm < 2 >-75 N / mm < 2 > and the rear unit tension is 35 N / mm < 2 >-45 N / mm < 2 > during first-pass rolling, and the front unit tension is 85 N / mm < 2 >-95 N / mm < 2 > and the rear unit tension is 55 N / mm < 2 >-65 N / mm < 2 > during second-pass rolling.

Description

Technical Field

[0001] The invention relates to the field of rolling of ultrapure ferritic stainless steel. Background Art

[0002] Ferritic stainless steel has some disadvantages and shortcomings as the chromium content increases, especially when the chromium content is ≥18%, which are mainly manifested in the high ductile-brittle transition temperature, poor room temperature and low temperature toughness, and high notch sensitivity, making it a problem for the widespread application of this type of steel. At the same time, ferritic stainless steel has a size effect, and the above disadvantages become more severe as the cross-sectional size of ferritic stainless steel increases.

[0003] Due to the large cross-sectional size and poor toughness of high-chromium ferritic stainless steel hot plates, the strip is easily broken when unwinding during pickling and annealing, and the cold plate cannot be produced further. The production of medium- and high-chromium ferritic stainless steel cold plates is difficult, and on-site production safety cannot be guaranteed.

[0004] Ultrapure ferritic stainless steel S44626 has super high corrosion resistance and is mostly used in coastal high chloride ion heavy corrosion environments, such as desalination condenser pipes, offshore photovoltaic support platforms and other projects. With the investment of more and more offshore and coastal projects, S44626 is more and more widely used and in greater demand. The main components of ultrapure ferritic stainless steel S44626 are Cr: 27%, Mo: 2%. It has a high alloy content and a room temperature impact energy of only 5-20J. It is prone to brittle fracture under rolling pressure. The strip breakage rate is relatively high during cold rolling, which affects the yield rate and production efficiency. Summary of the invention

[0005] The technical problem to be solved by the present invention is: how to achieve smooth cold rolling of S44626 without prone to brittle fracture by designing rolling deformation, rolling mill tension, plate shape target curve, roll roughness and other processes.

[0006] The technical solution adopted by the present invention is: a rolling method to prevent brittle fracture of S44626, during 20-roller cold rolling, by coordinated adjustment of rolling deformation, rolling mill tension, plate shape target curve, and roll roughness to prevent brittle fracture of S44626 during rolling; the rolling deformation includes the total rolling deformation controlled at 55%-65%, and during the 1st to 3rd rolling, constant deformation rolling is adopted, and the deformation is 12.5%-14.5%; when the rolling mill tension is set, during the 1st rolling, the front unit tension is 65N / mm 2- 75N / mm 2 , rear unit tension 35N / mm 2 -45N / mm 2 , during the second rolling, the front unit tension is 85N / mm 2 -95N / mm 2, rear unit tension 55N / mm 2 -65N / mm 2 ; During the third rolling, the front unit tension is 105N / mm 2 -115N / mm 2 , rear unit tension 75N / mm 2 -85N / mm 2 The plate shape target curve includes that the plate shape should maintain double-sided micro-edge waves throughout the entire rolling process, and all rolling passes should be controlled according to the target curve; during the first rolling pass, a roller with a roughness of 0.8μm-1.0μm is used, and after the 4th to 5th passes, it is replaced with a roller with a roughness of 0.35μm-0.45μm.

[0007] During the 1st to 3rd rolling passes, the rolling pressure is constant and the pressure is 400-440 tons.

[0008] During the 1st to 3rd rolling, at the start of each rolling, the front tension is 3-5N / mm less than the set tension. 2 When the rolling length reaches 80-120m, gradually increase the front tension to the set value. During the 1st to 3rd rolling, the edge shape value is negative 25N / mm 2 -Negative 15N / mm 2 , in the other rolling passes, the edge shape value is negative 45N / mm 2 -Negative 35N / mm 2 .

[0009] The beneficial effects of the present invention are as follows: the present invention develops a 20-roller cold rolling process of S44626, proposes a rolling control method that is relatively less likely to break the strip, and realizes the smooth cold rolling of S44626 by designing the rolling deformation, rolling mill tension, plate shape target curve, roll roughness and other processes. The S44626 is stably rolled without breaking the strip, the yield rate is improved, and the rolling safety is guaranteed. The control method for avoiding the breaking of the strip during the rolling of S44626 proposed by the present invention is highly operable and can be widely used. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a schematic diagram of the sunken plate-shaped double-sided micro-edge wave of the present invention. DETAILED DESCRIPTION

[0011] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0012] A rolling method to prevent brittle fracture of S44626, during 20-roller cold rolling, coordinated adjustments are made in four aspects: rolling deformation, mill tension, plate shape target curve, and roll roughness to prevent brittle fracture of S44626 during rolling; the key to continuous strip rolling of brittle materials is to ensure stable material state during the rolling process, especially the 1st to 3rd passes. The rolling deformation includes controlling the total rolling deformation at 55%-65%. During the 1st to 3rd passes of rolling, constant deformation rolling is adopted, and the deformation is 12.5%-14.5%; S44626 is very brittle, and in order to ensure stable rolling during the 1st to 3rd passes, a small tension should be ensured to start, to prevent strip breakage caused by excessive tension. When the mill tension is set, during the first pass of rolling, the front unit tension is 65N / mm 2- 75N / mm 2 , rear unit tension 35N / mm 2 -45N / mm 2 , during the second rolling, the front unit tension is 85N / mm 2 -95N / mm 2 , rear unit tension 55N / mm 2 -65N / mm 2 ; During the third rolling, the front unit tension is 105N / mm 2 -115N / mm 2 , rear unit tension 75N / mm 2 -85N / mm 2 The plate shape target curve includes that the plate shape should maintain double-sided micro-edge waves throughout the entire rolling process, and all rolling passes should be controlled according to the target curve; during the first rolling pass, a roller with a roughness of 0.8μm-1.0μm is used, and after the 4th to 5th passes, it is replaced with a roller with a roughness of 0.35μm-0.45μm.

[0013] During the 1st to 3rd rolling passes, the work hardening phenomenon of S44626 was not particularly severe, and the rolling pressure was constant and the pressure was 400-440 tons.

[0014] During the 1st to 3rd rolling, at the start of each rolling, the front tension is 3-5N / mm less than the set tension. 2 When the rolling length reaches 80-120m, gradually increase the front tension to the set value. During the 1st to 3rd rolling, the edge shape value is negative 25N / mm 2 -Negative 15N / mm 2 , in the other rolling passes, the edge shape value is negative 45N / mm 2 -Negative 35N / mm 2 .

[0015] The invention has been implemented in the rolling of super ultra-pure ferrite S44626 (4.0mm rolling 1.8mm) at TISCO's 8# rolling mill.

[0016] .

[0017] The deformation, tension and plate edge extension of the 1st to 3rd passes of the 8# rolling mill are set as above. A 1.0μm roll is used in the first pass, and a 0.4μm roll is replaced after 4 passes. The remaining passes are set according to the ordinary process.

[0018] The entire rolling process was stable and smooth, and no strip breakage occurred.

Claims

1. A rolling method for preventing brittle fracture of S44626, characterized in that: During the 20-roller cold rolling, the S44626 is prevented from brittle fracture during rolling by coordinated adjustment of rolling deformation, rolling mill tension, plate shape target curve, and roll roughness; the rolling deformation includes the total rolling deformation controlled at 55%-65%, and the 1st to 3rd rolling passes are rolled with constant deformation, and the deformation is 12.5%-14.5%; when the rolling mill tension is set, the front unit tension is 65N / mm during the first rolling pass. 2- 75N / mm 2 , rear unit tension 35N / mm 2 -45N / mm 2 , during the second rolling, the front unit tension is 85N / mm 2 -95N / mm 2 , rear unit tension 55N / mm 2 -65N / mm 2 ; During the third rolling, the front unit tension is 105N / mm 2 -115N / mm 2 , rear unit tension 75N / mm 2 -85N / mm 2 The plate shape target curve includes that the plate shape should maintain double-sided micro-edge waves throughout the entire rolling process, and all rolling passes should be controlled according to the target curve; during the first rolling pass, a roller with a roughness of 0.8μm-1.0μm is used, and after the 4th to 5th passes, it is replaced with a roller with a roughness of 0.35μm-0.45μm.

2. A rolling method for preventing brittle fracture of S44626 according to claim 1, characterized in that: During the 1st to 3rd rolling passes, the rolling pressure is constant and the pressure is 400-440 tons.

3. A rolling method for preventing brittle fracture of S44626 according to claim 1, characterized in that: During the 1st to 3rd rolling, at the start of each rolling, the front tension is 3-5N / mm less than the set tension. 2 When the rolling length reaches 80-120m, gradually increase the front tension to the set value.

4. A rolling method for preventing brittle fracture of S44626 according to claim 1, characterized in that: During the 1st to 3rd rolling, the edge shape value is negative 25N / mm 2 -Negative 15N / mm 2 , in the other rolling passes, the edge shape value is negative 45N / mm 2 -Negative 35N / mm 2 .

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