Production process of ultra-pure ferrite without using a tension leveler to solve plate shape problems

Abstract

A production process for ultrapure ferrite strips that does not require a strip leveling machine to solve the strip shape problem includes: 1) controlling the strip shape at the edge of the rolling mill within ±20mm; 2) furnace cooling: a perforated plate is installed above the strip, with cooling holes evenly distributed on the plate surface. Multiple pressure-reducing water pools are installed above the perforated plate. Cooling water is first filled in the pressure-reducing water pools, then overflows onto the upper surface of the perforated plate, and then evenly sprinkled onto the surface of the steel plate through the cooling holes; 3) adjusting the finishing mill roll crown height to 0.04~0.07mm; simultaneously adjusting the finishing mill tension = (unit tension * strip width * strip thickness) * [1 + (14%~16%)]; 4) no strip leveling machine is used after the strip exits the finishing mill. This invention achieves the ability to solve strip shape problems in continuous rolling lines without using a strip leveler by controlling the strip shape exiting the rolling mill, changing the water cooling method in the furnace cooling section, and optimizing the configuration parameters of the finishing machine. It avoids the quality defects of attachments and uneven stripes in production lines using strip levelers, and saves the related costs incurred by using strip levelers.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical steel rolling technology, and in particular relates to a production process for ultrapure ferrite without using a tension leveler to solve the plate shape problem. Background Technology

[0002] Currently, major stainless steel factories use tension leveling machines to improve the shape of steel strips when producing ultra-pure ferritic stainless steel products. There are two problems with using tension leveling machines: a) there is a chance of foreign matter adhering and causing defect transfer when using tension leveling machines; b) using tension leveling machines can aggravate the uneven stripe defects on the plate surface. Summary of the Invention

[0003] The purpose of this invention is to provide a production process for ultrapure ferrite steel plates that does not require a tension leveler to solve plate shape problems. This process can effectively control the plate shape of ultrapure ferrite steel plates without the use of a tension leveler, thereby avoiding steel plate quality defects caused by the use of a tension leveler.

[0004] To achieve the above objectives, the present invention employs the following technical solution:

[0005] A production process for ultrapure ferrite that does not require a tension leveler to solve plate shape issues includes:

[0006] 1) When the steel strip exits the rolling mill, the edge profile should be controlled within ±20mm.

[0007] 2) The water cooling method of the furnace cooling section is as follows: a perforated plate is installed above the strip steel, and cooling holes are evenly distributed on the surface of the perforated plate. Multiple pressure-reducing water pools are installed above the perforated plate. The pressure-reducing water pools are connected to cooling water pipes. The cooling water is first filled in the pressure-reducing water pools, and then overflows to the upper surface of the perforated plate. Then it is evenly sprinkled onto the surface of the steel plate through the cooling holes to cool the steel plate.

[0008] 3) Adjust the crown height of the finishing mill rolls to 0.04-0.07mm; at the same time, adjust the finishing mill tension = (unit tension * steel strip width * steel strip thickness) * [1 + (14%-16%)];

[0009] 4) After the strip steel is finished, a tension leveling machine is not used.

[0010] In step 3) above, the height of the finishing mill roll crown is adjusted to 0.06mm.

[0011] In step 3) above, adjust the finishing machine tension = (unit tension * steel strip width * steel strip thickness) * (1 + 15%).

[0012] The unit tension for the 200 series finishing mill, based on strip thickness, is:

[0013]

[0014]

[0015] The unit tension for the 300 series finishing mill, based on strip thickness, is:

[0016] The unit tension for the 400 series finishing mill, based on strip thickness, is:

[0017]

[0018]

[0019] Compared with existing technologies, the beneficial effects of this invention are:

[0020] This invention achieves the ability to solve strip shape problems in continuous rolling lines without using a strip leveler by controlling the strip shape exiting the rolling mill, changing the water cooling method in the furnace cooling section, and optimizing the configuration parameters of the finishing machine. It avoids the quality defects of attachments and uneven stripes in production lines using strip levelers, and saves the related costs incurred by using strip levelers. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the water cooling method in the furnace cooling section of the present invention.

[0022] In the diagram: 1-perforated plate, 2-cooling water pipe, 3-pressure reducing water tank, 4-strip steel, 5-cooling hole. Detailed Implementation

[0023] The embodiments of the present invention will be further described below with reference to the accompanying drawings:

[0024] Example 1:

[0025] The example is the production of 022Cr18NbTi (AISI 441) ultrapure ferritic stainless steel plate.

[0026] A production process for ultrapure ferrite that does not require a tension leveler to solve plate shape issues includes:

[0027] 1) The strip profile of the steel strip exiting the mill is controlled by adjusting the taper of the intermediate roll and the force on the bending roll. When the steel strip exits the mill, the edge profile is controlled within ±20mm.

[0028] 2) The water cooling method of the furnace cooling section is as follows: A perforated plate 1 is set above the strip 4. Cooling holes 5 are evenly distributed on the surface of the perforated plate 1. Multiple pressure-reducing water pools 3 are set above the perforated plate 1. The pressure-reducing water pools 3 are connected to the cooling water pipes 2. The cooling water is first filled in the pressure-reducing water pools 3, then overflows to the upper surface of the perforated plate 1, and then evenly sprinkled onto the surface of the strip 3 through the cooling holes 5 to uniformly cool the steel plate.

[0029] This invention changes the original method of directly spraying cooling water onto the steel plate through a spray bar. Instead, the cooling water is first sprayed into a pressure-reducing water tank 3 and then overflows onto a perforated plate 1 with uniformly distributed cooling holes 5. This achieves uniform and pressureless cooling of the strip steel 4, resulting in uniform cooling of the strip steel 4 surface and improving the flatness of the exit plate. Generally, the exit plate shape can be controlled within ±15mm.

[0030] 3) Adjust the height of the finishing mill roll crown from the original 0.12mm to 0.06mm; at the same time, increase the tension before and after the finishing process, that is, increase it by 15% on the basis of the original tension, that is: adjust the finishing mill tension = (unit tension * steel strip width * steel strip thickness) * [1 + (15%)].

[0031] The unit tension of the examples is shown in Table 1;

[0032] Table 1

[0033]

[0034] 4) After finishing, do not use a tension leveler; directly wind up the machine.

[0035] 5) Strictly control the parallelism of each roller group in the production line, with the accuracy controlled within 3mm. If the parallelism of the roller group exceeds the control value, it will easily cause edge waviness to be generated under the action of tensile stress on the edge of the steel strip.

[0036] Since implementing the above process, a steel plant has produced a total of 25,208 tons of ferritic stainless steel. The plate qualification rate is 100%, and the surface quality of the steel plates is good, with no defects such as attachments or uneven stripes.

Claims

1. A production process for ultrapure ferrite that does not use a tension leveler to solve plate shape problems, characterized in that it includes: 1) When the steel strip exits the rolling mill, the edge profile should be controlled within ±20mm; 2) The water cooling method of the furnace cooling section is as follows: a perforated plate is installed above the strip steel, and cooling holes are evenly distributed on the surface of the perforated plate. Multiple pressure-reducing water pools are installed above the perforated plate. The pressure-reducing water pools are connected to the cooling water pipes. The cooling water is first filled in the pressure-reducing water pools, and then overflows to the upper surface of the perforated plate. Then it is evenly sprinkled onto the surface of the steel strip through the cooling holes to cool the steel strip. 3) Adjust the crown height of the finishing mill rolls to 0.04-0.07mm; at the same time, adjust the finishing mill tension = (unit tension * steel strip width * steel strip thickness) * [1 + (14%-16%)]; 4) After the strip steel has been finished, a tension leveling machine is not used; The unit tension for the 200 series finishing mill, based on strip thickness, is: Steel strip thickness (mm) Back tension (kN) Front tension (kN) 0.200-0.369 152 188 0.370-0.439 140 156 0.440-0.519 130 143 0.520-0.599 120 130 0.600-0.699 104 118 0.700-0.799 100 111 0.800-0.999 90 105 1.000-1.299 82 95 1.300-1.599 70 80 1.600-1.999 56 68 2.000-2.499 52 60 2,500-3,000 43 51; The unit tension for the 300 series finishing mill, based on strip thickness, is: Steel strip thickness (mm) Back tension (kN) Front tension (kN) 0.200-0.369 168 191 0.370-0.439 140 158 0.440-0.519 140 153 0.520-0.599 132 143 0.600-0.699 126 136 0.700-0.799 114 124 0.800-0.999 90 103 1.000-1.299 80 87 1.300-1.599 66 74 1.600-1.999 58 66 2.000-2.499 52 60 2,500-3,000 48 55; The unit tension for the 400 series finishing mill, based on strip thickness, is: Steel strip thickness (mm) Back tension (kN) Front tension (kN) 0.200-0.369 176 186 0.370-0.439 168 178 0.440-0.519 130 140 0.520-0.599 125 135 0.600-0.699 117 124 0.700-0.799 106 113 0.800-0.999 98 105 1.000-1.299 84 98 1.300-1.599 76 83 1.600-1.999 60 67 2.000-2.499 50 60 2.500-3.000 43 50。 2. The production process for ultrapure ferrite without using a tension leveling machine to solve the plate shape problem according to claim 1, characterized in that, In step 3) above, adjust the height of the finishing mill roll crown to 0.06mm.

3. The production process for ultrapure ferrite without using a tension leveling machine to solve the plate shape problem according to claim 1, characterized in that, In step 3) above, adjust the finishing machine tension = (unit tension * steel strip width * steel strip thickness) * (1 + 15%).

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