A rolling method for achieving high reduction in carbon die steel passes

Abstract

The invention discloses a rolling method for achieving large-pass reduction of carbon die steel. The process is as follows: firstly, the thickness of a billet is determined, the billet is subjected to heating treatment and rough descaling, and then rolling treatments are performed according to different target thicknesses t (mm). When t≥250, the number of roughing strip-loaded passes is ≤2, 1 roughing pass is performed without a roughing pass, and 1 finishing pass is performed; when 220≤t<250, the number of roughing strip-loaded passes is ≤3, and 1 finishing pass is performed; when 180≤t<220, the number of roughing strip-loaded passes is ≤4, 1 roughing pass is performed without a roughing pass, and 1 finishing pass is performed; when 150≤t<180, the number of roughing strip-loaded passes is ≤5, and 1 finishing pass is performed; when 120≤t<150, the number of roughing strip-loaded passes is ≤6, 1 roughing pass is performed without a roughing pass, and 1 finishing pass is performed; when 100≤t<120, the number of roughing strip-loaded passes is ≤7, and 1 finishing pass is performed; and the rolling operation is completed. The rolling process of the present invention can achieve large reduction in passes, eliminate steel loading restrictions and improve the overall rolling rhythm.

Description

Technical Field

[0001] The invention belongs to the technical field of wide and thick plate rolling, and particularly relates to a rolling method for achieving high pass reduction of carbon die steel. Background Art

[0002] Carbon mold steel, that is, carbon structural steel with grades S35C, S40C, S45C, S50C, and S55C, is mainly used to make plastic molds. However, it may have the following defects: internal pinholes or shrinkage cavities will affect customer use, and repair welding will increase the customer's processing costs, and serious problems may lead to scrapping. Therefore, carbon mold steel requires a large reduction during the rolling process to improve or eliminate internal defects.

[0003] Current methods for producing carbon mold steel often result in quality issues, impacting customer use. Furthermore, carbon mold steel requires warm furnace loading and conventional rolling, and cannot be mixed with controlled-rolled material. These loading restrictions hinder overall production capacity. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention provides a rolling method for achieving large pass reduction of carbon die steel, which can achieve large pass reduction, eliminate steel loading restrictions and improve the overall rolling rhythm.

[0005] The present invention is achieved through the following technical solutions:

[0006] A rolling method for achieving high reduction of carbon die steel passes comprises the following steps:

[0007] Step 1) Determine the thickness of the mold steel blank to be 320 mm, push the blank into the heating furnace for heating, and the slab must be heated evenly and burned through. After completion, it is sent out by a roller table for rough descaling;

[0008] Step 2) The billet processed in step 1) is rolled using a single-stand rolling process. The rolling force limit is released during rough rolling. The target thickness of the finished product is set to t. The rolling process is as follows:

[0009] When t≥250mm, the number of rough rolling passes is ≤2 + 1 rough rolling pass + 1 finishing pass to level the plate shape, and the total number of rolling passes is ≤4;

[0010] When 220mm≤t<250mm, the number of rough rolling passes is ≤3 + the number of finishing passes is 1 to level the plate shape, and the total number of rolling passes is ≤4;

[0011] When 180mm≤t<220mm, the number of rough rolling passes is ≤4 + 1 rough rolling pass + 1 finishing pass to level the plate shape, and the total number of rolling passes is ≤6;

[0012] When 150mm≤t<180mm, the number of rough rolling passes is ≤5+1 finishing pass to level the plate shape, and the total number of rolling passes is ≤6;

[0013] When 120mm≤t<150mm, the number of rough rolling passes is ≤6 + 1 rough rolling pass + 1 finishing pass to level the plate shape, and the total number of rolling passes is ≤8;

[0014] When 100mm≤t<120mm, the number of rough rolling passes is ≤7+1 finishing pass to level the plate shape, and the total number of rolling passes is ≤8;

[0015] Step 3) straightening and stack cooling the billet after the rolling process in step 2) to complete the operation.

[0016] Preferably, in step 2), when t≥120 mm, the reduction in the last pass of the rough rolling strip load is ≥30 mm.

[0017] Preferably, in step 2), when 100 mm ≤ t < 120 mm, the reduction in the last pass of the rough rolling strip load is ≥ 25 mm.

[0018] Preferably, in step 2), when t is 100-180 mm, the average reduction in the last three passes of rough rolling is ≥28 mm.

[0019] Preferably, in step 2), the reduction in one finishing rolling pass is 3 to 10 mm.

[0020] The beneficial effects of the present invention are as follows:

[0021] (1) Our factory previously used a dual-stand model (existing technology) to produce 129 pieces of carbon die steel with a thickness of more than 100 mm. The pass compliance rate was 32.56%, and only 3 pieces met the requirements for the final pass reduction. After adopting the method of the present invention, 159 pieces of carbon die steel with a thickness of more than 100 mm were produced in a single-stand model. The pass compliance rate increased to 64.78%, and the final pass reduction compliance rate increased to 76.1%.

[0022] (2) The present invention adjusts the dual-stand production mode to a single-stand mode, which reduces the total number of passes while ensuring the reduction in each pass, shortens the rolling time, and improves production efficiency. The single-stand mode can eliminate the furnace loading position restriction of carbon die steel, and achieve mixed loading with other steel types without affecting the production rhythm, laying the foundation for the subsequent promotion of hot loading of die steel within 24 hours to increase production capacity.

[0023] (3) The carbon die steel produced by the method of the present invention was piled and cooled for 24 hours and then disassembled for inspection. The surface quality was good. The thickness (6 points) and width and length of the head, middle and tail sides were measured. The measurement results were all qualified and could be promoted and applied. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below with reference to specific embodiments.

[0025] Example 1

[0026] A rolling method for achieving high reduction of carbon die steel passes, comprising the following steps:

[0027] (1) Determine the thickness of the mold steel blank to be 320 mm, push the blank into the heating furnace for heating, and then send it out by the roller for rough descaling.

[0028] (2) The billet after the above treatment is rolled using a single-stand rolling process (N roughing passes + 1 finishing pass, where the finishing pass is used to level the plate shape). The roughing process is required to release the rolling force limit. To ensure a large reduction in steel rolling, the slab must be heated evenly and burned through. The target thickness of the finished product is set to t. The rolling process is as follows:

[0029] When t≥250mm, the first pass reduction is required to be small to play a transition role, so as to ensure a large reduction in the last pass of rough rolling. The number of rough rolling passes with load is ≤2 (the last pass of rough rolling with load has a reduction of ≥30mm) + 1 rough rolling pass without load + 1 finishing pass to level the plate shape (reduction of 3-10mm), and the total number of rolling passes is ≤4;

[0030] When 220mm≤t<250mm, the number of rough rolling passes is ≤3 (the last rough rolling pass has a reduction of ≥30mm) + one finishing pass for flattening the plate (reduction of 3-10mm), and the total number of rolling passes is ≤4;

[0031] When 180mm≤t<220mm, the number of rough rolling passes is ≤4 (the last rough rolling pass has a reduction of ≥30mm) + 1 rough rolling pass + 1 finishing pass to level the plate (reduction of 3-10mm), and the total number of rolling passes is ≤6;

[0032] When 150mm≤t<180mm, the number of rough rolling passes is ≤5 (the last rough rolling pass has a reduction of ≥30mm) + one finishing pass for flattening the plate (reduction of 3-10mm), and the total number of rolling passes is ≤6;

[0033] When 120mm≤t<150mm, the number of rough rolling passes is ≤6 (the last rough rolling pass has a reduction of ≥30mm) + 1 rough rolling pass + 1 finishing pass to level the plate (reduction of 3-10mm), and the total number of rolling passes is ≤8;

[0034] When 100mm≤t<120mm, the number of rough rolling passes is ≤7 (the last rough rolling pass has a reduction of ≥25mm) + 1 finishing pass to level the plate (reduction of 3 to 10mm), and the total number of rolling passes is ≤8.

[0035] When the thickness of the finished product is between 100 and 180 mm, it is required to ensure that the average reduction of the last three loading passes of rough rolling is ≥ 28 mm, and the larger the better.

[0036] (3) The rolled billet is straightened and cooled to complete the operation.

[0037] Example 2

[0038] A carbon die steel, grade S35C, with a target thickness of 105 mm, is rolled according to the process methods described in the prior art and Example 1.

[0039] The rolling process using existing technology is: double-stand rolling, 5 rough rolling passes + 2 finishing rolling passes + 1 idle pass, the last rough rolling pass with load has a reduction of 24.34mm (does not meet the 25mm requirement), and the pure rolling time is 36.09s.

[0040] The specific process of rolling using the method shown in Example 1 is shown in Table 1 below:

[0041] Table 1 E3407003000 rolling process

[0042]

[0043] Note to Table 1: Stand number R indicates rough rolling, and stand number F indicates finishing rolling.

[0044] As can be seen from Table 1, the rolling method shown in Example 1 is adopted, that is, 7 rough rolling passes + 1 finishing rolling pass for leveling (the number of passes remains unchanged compared with the prior art), the last rough rolling pass with load has a reduction of 28.58 mm (an increase of 4.24 mm compared with the prior art, meeting the 25 mm requirement), and the pure rolling time is 32.82 s (shortened by 3.27 s compared with the prior art).

[0045] After the pile has cooled for 24 hours, it is dismantled for inspection. The surface quality is good. The thickness (6 points) and width and length of the head, middle and tail sides are measured as follows:

[0046] The target thickness is 105mm, and the actual measured thickness is: the thickness of the head of the operating side is 104.5mm, the thickness of the middle of the operating side is 104.9mm, and the thickness of the tail of the operating side is 105.4mm; the thickness of the head of the transmission side is 104.7mm, the thickness of the middle of the transmission side is 104.85mm, and the thickness of the tail of the transmission side is 105.1mm.

[0047] The target width is 2470mm, the actual measured head width is 2480mm, the middle width is 2485mm, and the tail width is 2485mm.

[0048] The target length is 12192mm, and the actual measured length of the arc excluding the head is 12330mm.

[0049] The measurement results and dimensions are all qualified.

[0050] Example 3

[0051] A carbon die steel, grade S45C, with a target thickness of 160 mm, is rolled according to the process methods described in the prior art and in Example 1.

[0052] The rolling process using existing technology is: double-stand rolling, 5 rough rolling passes + 2 finishing rolling passes + 1 idle pass, the last rough rolling pass with load has a reduction of 21.54mm (does not meet the 30mm requirement), and the pure rolling time is 23.60s.

[0053] The specific process of rolling using the method shown in Example 1 is shown in Table 2 below:

[0054] Table 2 E3409069000 rolling process

[0055]

[0056] Note to Table 2: Stand number R indicates rough rolling, and stand number F indicates finishing rolling.

[0057] As can be seen from Table 2, the rolling method shown in Example 1 is adopted, that is, 5 rough rolling passes + 1 finish rolling pass for leveling (2 passes less than the number of passes in the prior art), the last rough rolling pass with load has a reduction of 31.58 mm (10.04 mm more than the prior art, meeting the 30 mm requirement), and the pure rolling time is 20.30 s (3.3 s shorter than the prior art).

[0058] After the pile has cooled for 24 hours, it is dismantled for inspection. The surface quality is good. The thickness (6 points) and width and length of the head, middle and tail sides are measured as follows:

[0059] The target thickness is 160mm, and the actual measured thickness is: the thickness of the head of the operating side is 159.6mm, the thickness of the middle of the operating side is 159.8mm, and the thickness of the tail of the operating side is 160mm; the thickness of the head of the transmission side is 159.1mm, the thickness of the middle of the transmission side is 159.4mm, and the thickness of the tail of the transmission side is 159.65mm.

[0060] The target width is 2240mm, the actual measured head width is 2255mm, the middle width is 2255mm, and the tail width is 2260mm.

[0061] The target length is 7300mm, and the actual measured length of the arc excluding the head is 7360mm.

[0062] The measurement results and dimensions are all qualified.

[0063] Example 4

[0064] A carbon die steel, grade S45C, with a target thickness of 230 mm, is rolled according to the process methods described in the prior art and in Example 1.

[0065] The rolling process using existing technology is: double-stand rolling, 2 rough rolling passes + 1 idle pass + 2 finishing passes + 1 idle pass, the last pass with load has a reduction of 21.13mm (does not meet the 30mm requirement), and the pure rolling time is 22.32s.

[0066] The specific process of rolling using the method shown in Example 1 is shown in Table 3 below:

[0067] Table 3 E3409226000 rolling process

[0068]

[0069] Note to Table 3: Stand number R indicates rough rolling, and stand number F indicates finishing rolling.

[0070] As can be seen from Table 3, the rolling method shown in Example 1 is adopted, that is, 3 rough rolling passes + 1 finish rolling pass for leveling (2 passes less than the number of passes in the prior art), the last rough rolling pass with load has a reduction of 31.36 mm (10.23 mm more than the prior art, meeting the 30 mm requirement), and the pure rolling time is 12.95 s (9.4 s shorter than the prior art).

[0071] After the pile has cooled for 24 hours, it is dismantled for inspection. The surface quality is good. The thickness (6 points) and width and length of the head, middle and tail sides are measured as follows:

[0072] The target thickness is 230mm, and the actual measured thickness is: the thickness of the head of the operating side is 229.8mm, the thickness of the middle of the operating side is 231mm, and the thickness of the tail of the operating side is 230.1mm; the thickness of the head of the transmission side is 231.5mm, the thickness of the middle of the transmission side is 231.7mm, and the thickness of the tail of the transmission side is 231.2mm.

[0073] The target width is 2250mm, the actual measured head width is 2265mm, the middle width is 2270mm, and the tail width is 2275mm.

[0074] The target length is 5350mm, and the actual measured length of the arc after removing the head is 5400mm.

[0075] The measurement results and dimensions are all qualified.

[0076] The embodiments described above are only some of the embodiments of the present invention, rather than all of the embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but merely represents selected embodiments of the present invention. The scope of protection of the present invention shall be based on the scope required by the claims. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making creative efforts shall fall within the scope of protection of the present invention.

Claims

1. A rolling method for achieving high reduction of carbon die steel, characterized in that: The following steps are involved: Step 1) Determine the thickness of the die steel blank to be 320 mm. Push the blank into the heating furnace for heating. The blank must be heated evenly and burned through. After completion, it is sent out by rollers for rough descaling. Step 2) The billet processed in step 1) is rolled using a single-stand rolling process. The rolling force limit is released during rough rolling. The target thickness of the finished product is set to t. The rolling process is as follows: When t≥250 mm, the number of rough rolling passes is ≤2 + 1 rough rolling pass + 1 finishing pass to level the plate shape, and the total number of rolling passes is ≤4; When 220 mm ≤ t < 250 mm, the number of rough rolling passes is ≤ 3 + the number of finishing passes is 1 to level the plate shape, and the total number of rolling passes is ≤ 4; When 180 mm ≤ t < 220 mm, the number of rough rolling passes is ≤ 4 + 1 rough rolling pass + 1 finishing pass to level the plate shape, and the total number of rolling passes is ≤ 6; When 150 mm ≤ t < 180 mm, the number of rough rolling passes is ≤ 5 + 1 finishing pass to level the plate shape, and the total number of rolling passes is ≤ 6; When 120 mm ≤ t < 150 mm, the number of rough rolling passes is ≤ 6 + 1 rough rolling pass + 1 finishing pass to level the plate shape, and the total number of rolling passes is ≤ 8; When 100 mm ≤ t < 120 mm, the number of roughing passes is ≤ 7 + 1 finishing pass to level the plate shape, and the total number of rolling passes is ≤ 8; When t≥120 mm, the reduction of the last pass of rough rolling with load is ≥30 mm; When 100 mm≤t<120 mm, the reduction of the last pass of rough rolling with load is ≥25 mm; When t is 100-180 mm, the average reduction in the last three passes of rough rolling with load is ≥28 mm; The reduction in one finishing pass is 3~10 mm; Step 3) straightening and cooling the billet after rolling in step 2) to complete the operation.

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