Method for producing very thin gauge stainless steel on an eighteen roll five stand tandem cold mill

Abstract

The eighteen-roll five-stand tandem cold rolling mill produces 1250mm width 0.35-0.55mm thickness ultra-thin specification 304 stainless steel, which can overcome various problems such as low efficiency, low yield and poor consistency of the traditional single-stand mode, but at the same time, the multi-stand tandem cold rolling mill has the shortcomings of difficult shape control of 0.6mm or less specification stainless steel plate, high requirement of raw material defect rate and easy breaking of the strip in the rolling process, the present application develops a new process to finely design the deformation of each stand, rolling force, tension, unit tension and bending roll value, and the actual production verifies that the related parameter setting can stably and efficiently produce thin specification 304 stainless steel with high quality.

Description

Technical Field

[0001] This invention relates to the field of stainless steel cold rolling, and more particularly to a method for producing ultra-thin stainless steel using an 18-roll, 5-stand cold rolling mill. Background Technology

[0002] In recent years, the use of 0.35-0.55mm stainless steel has increased significantly in various industries such as home appliances and decoration. At the same time, thinner stainless steel has higher prices and profits compared to thicker stainless steel, and the added value of the product is greater. However, the traditional single-stand process for producing thin stainless steel has various disadvantages such as low efficiency, low yield, and poor consistency. Continuous rolling production can solve these problems, but multi-stand cold continuous rolling mills are difficult to control the shape of stainless steel plates with a diameter of less than 0.6mm due to the design of rolling mills in series. They also have high requirements for raw material defect rate and are prone to strip breakage during the rolling process. Therefore, the design limit is the thinnest size of 0.6mm. In order for the continuous rolling production mode to meet the production requirements of ultra-thin stainless steel with a diameter of 0.35-0.55mm, it is necessary to develop new technologies to adapt to market development.

[0003] The purpose of this invention is to achieve continuous rolling of 0.35-0.55mm 304 stainless steel in five stands, ensuring that: (1) the continuous rolling process is smooth without strip breakage, deviation and edge pulling; (2) the thickness of the finished product is within the tolerance range; (3) the surface is free of surface defects such as roller marks, slip marks, emulsion marks, etc.; and (4) the plate shape is flat and can smoothly pass through subsequent annealing, pickling, leveling, edge trimming and other processes to finally form finished stainless steel coils. Summary of the Invention

[0004] The purpose of this invention is to address the above-mentioned problems by providing a method for producing ultra-thin stainless steel using an 18-roll, 5-stand cold rolling mill.

[0005] The objective of this invention is achieved as follows: A method for producing ultra-thin stainless steel using an 18-roll, 5-stand cold rolling mill, comprising the following aspects: (1) Raw material requirements: Defect control of raw materials: detection of heavy scales, perforations, inclusions, and edge cracks with a depth greater than 2mm; (2) Roll system configuration: Requirements for the roughness and convexity of the work rolls: 1. Work roll convexity on stand 1: flat, roughness μm: 0.8-1.2; 2. Work roll convexity on stand 2: flat, roughness μm: 0.8-1.2; 3. Work roll convexity on stand 3: flat, roughness μm: 0.8-1.2. Roughness μm: 0.8-1.0; 4-stand upper work roll crown: flat, roughness μm: 0.6-0.8; 5-stand upper work roll crown: 10 marks (0.1mm), roughness μm: 0.12-0.15; 1-stand lower work roll crown: flat, roughness μm: 0.8-1.2; 2-stand lower work roll crown: flat, roughness μm: 0.8-1.2; 3-stand lower work roll crown: flat, roughness μm: 0.8-1.0; 4-stand lower work roll crown: flat, roughness μm: 0.2-0. 4, 5 stand lower work roll crown: flat, roughness μm: 0.12-0.15; intermediate roll cone length 460mm; (3) Rolling parameter design: 1) Deformation amount and rolling force of each stand: 1 stand deformation amount %: 33-40, 2 stand deformation amount %: 30-35, 3 stand deformation amount %: 26-30, 4 stand deformation amount %: 23-27, 5 stand deformation amount %: 15-21, rolling force 10000-14000KN; 2) Unit tension of each stand: entrance unit tension MPa: 80-85, Unit tension of frame 1 (MPa): 150-170; Unit tension of frame 2 (MPa): 180-200; Unit tension of frame 3 (MPa): 200-220; Unit tension of frame 4 (MPa): 200-220; Unit tension of frame 5 (MPa): 220-230; 3) Bending roller values ​​of each frame: Bending roller value % of frame 1: 83-85; Bending roller value % of frame 2: 48-50; Bending roller value % of frame 3: 50-52; Bending roller value % of frame 4: -52--50; Bending roller value % of frame 5: -62--60.

[0006] (1) The thickness of the raw material is 2.35-2.5mm, and the maximum deformation rate is 78%-85%.

[0007] The beneficial effects of this invention are: (1) The continuous rolling production mode can significantly improve the surface consistency of thin-gauge products and meet customers' needs for product stability. (2) It reduces the cutting of the head and tail sections, and the cold rolling yield of the product can reach more than 99%, which is more than 3.8% higher than the single-stand mode. Taking a monthly production of 1,000 tons as an example, it can reduce cutting losses by at least RMB 200,000 per month. (3) It has high production efficiency. The continuous rolling production line can achieve a TV of more than 75, which is more than 38% higher than the single-stand mode. (4) At present, the Taiyuan Iron & Steel cold continuous rolling mill has produced more than 8,400 tons of 0.35-0.55mm, which has achieved good market response. Detailed Implementation

[0008] (1) First of all, for the continuous rolling production of 0.35-0.55mm thin stainless steel, there are relatively strict requirements for raw materials: 1) The thickness of the raw material is between 2.35-2.5mm, and the maximum deformation rate is about 78%-85%, which can make the rolling mill continuously roll in a relatively stable state and minimize the possibility of strip pulling or breaking; 2) Defect control of raw materials: the previous process must detect heavy scale, perforation, inclusions and edge cracks with a depth greater than 2mm to avoid the expansion of defects during the rolling process and eventually cause the strip to tear and break.

[0009] (2) Secondly, the requirements for the roll system configuration are, on the one hand, to control the final plate shape at the mill exit, and on the other hand, to ensure good surface roughness and smoothness of the finished product, including: 1) The roughness and convexity requirements of the work rolls are as shown in the table below. 2) The cone length of the intermediate roll is 460mm.

[0010]

[0011] (3) Rolling parameter design: 1) Deformation and rolling force of each stand: The first three stands fully utilize the plasticity of the material to quickly roll the steel plate to a thickness close to the target thickness. The last two stands adjust the surface roughness and smoothness of the strip. Since the target thickness of 0.35-0.55mm is difficult to control in continuous rolling mills, the window for the distribution of deformation of each stand is small. It is necessary to give full play to the maximum rolling capacity of each stand. Therefore, the deformation range of each stand is set as shown in the table below.

[0012]

[0013] The rolling force should be matched according to the amount of deformation, but the rolling force should not exceed 14000KN to avoid sudden strip breakage accidents.

[0014] 2) Tension of each stand and unit tension: The unit tension of each stand is set to approximately 35% of the material's yield strength, ensuring the strip can smoothly bite into the rolls. Appropriate tension also reduces strip breakage between stands and improves strip profile. Therefore, for thin-gauge production, the unit tension is uniformly set as shown in the table below.

[0015]

[0016] The total tension of each frame is adjusted according to the actual thickness of the strip. If slippage or abrasion occurs during the process, the unit tension should be finely adjusted to prevent slippage and abrasion.

[0017] 3) Bending roll values ​​for each stand: The parameter design direction is to prioritize stable rolling for the first 3 stands, with the thickness of the strip on both sides being about 0.025mm thicker than the center to ensure that the strip does not deviate and facilitate strip position control. For the last two stands, since the strip thickness becomes thinner rapidly, the thickness of the strip on both sides is less than 3mm thinner than the center. This avoids serious differences in the thickness of the strip and reduces the edge tension of the strip, greatly reducing the possibility of strip tearing and breakage due to stress concentration caused by edge defects during the strip rolling process. Therefore, the bending roll values ​​are uniformly set as shown in the table below when producing thin specifications.

[0018]

[0019] Production precautions: (1) The steel strip may slip or wobble within 3-5 meters of the weld. Increasing the bending roller value can improve this. If the deviation exceeds 20mm, stop the machine first and then adjust. (2) The working roller should be replaced in time according to the forward slip value (≤-0.5%). (3) If the plate shape is found to be abnormal at the exit of the 5th frame, the working roller should be replaced immediately. Example 1

[0020] The 304 stainless steel has a width of 1250mm, a thickness of 2.44mm, and a target rolling thickness of 0.405mm. The parameter settings are as follows:

[0021] The 304 stainless steel has a width of 1250mm and a thickness of 2.50mm, with a target rolling thickness of 0.512mm. The parameter settings are as follows:

[0022] 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 method for producing ultra-thin stainless steel using an 18-roll, 5-stand cold rolling mill, characterized in that: Including the following aspects: (1) Requirements for raw materials: Defect control of raw materials: detect heavy scales, perforations, inclusions and edge cracks with a depth greater than 2 mm that are larger than 10 mm; (2) Roller configuration: Requirements for the surface roughness and crown of the working rolls:

1. Crown of the working roll on the frame: flat, surface roughness μm: 0.8-1.2; 2. Crown of the working roll on the frame: flat, surface roughness μm: 0.8-1.2; 3. Crown of the working roll on the frame: flat, surface roughness μm: 0.8-1.0; 4. Crown of the working roll on the frame: flat, surface roughness μm: 0.6-0.8; 5. Crown of the working roll on the frame: 10 marks, i.e., 0.1mm, surface roughness μm:

0. 0.12-0.15, 1. Lower work roll crown: flat, roughness μm: 0.8-1.2; 2. Lower work roll crown: flat, roughness μm: 0.8-1.2; 3. Lower work roll crown: flat, roughness μm: 0.8-1.0; 4. Lower work roll crown: flat, roughness μm: 0.2-0.4; 5. Lower work roll crown: flat, roughness μm: 0.12-0.15; Intermediate roll cone length 460mm; (3) Rolling parameter design: 1) Deformation and rolling force of each stand: 1st stand deformation %: 33-40, 2nd stand deformation %: 30-35, 3rd stand deformation %: 26-30, 4th stand deformation %: 23-27, 5th stand deformation %: 15-21, rolling force 10000-14000KN; 2) Unit tension of each stand: entrance unit tension MPa: 80-85, 1st stand unit tension MPa: 150-170, 2nd ... Force MPa: 180-200, 3-stand unit tension MPa: 200-220, 4-stand unit tension MPa: 200-220, 5-stand unit tension MPa: 220-230; 3) Bending roller values ​​for each stand: 1-stand bending roller value %: 83-85, 2-stand bending roller value %: 48-50, 3-stand bending roller value %: 50-52, 4-stand bending roller value %: (-52)-(-50), 5-stand bending roller value %: (-62)-(-60).

2. The method for producing ultra-thin stainless steel using an 18-roll, 5-stand cold rolling mill according to claim 1, characterized in that: (1) The thickness of the raw material is 2.35-2.5mm, and the maximum deformation rate is 78%-85%.

Images