A method for manufacturing a high-carbon martensitic stainless steel hot-rolled coil

Abstract

The application discloses a manufacturing method of high-carbon martensitic stainless steel hot-rolled coiled sheet, which comprises the following steps: slab heating, heating section and second section furnace temperature is 1280-1300 DEG C, soaking section furnace temperature is 1220-1250 DEG C, total heating time is 180-230 min, and the soaking section holding time is greater than or equal to 50 min; adopting superhigh pressure water descaling, water pressure is 30-40 MPa; after descaling, the slab end face center part temperature is 1100-1160 DEG C before entering the roughing mill, roughing adopts 5 passes, the reduction is respectively 12-18%, 18-26%, 30-38%, 30-38%, 35-40%, and the finish rolling temperature is greater than or equal to 1100 DEG C; finish rolling adopts 7 passes, the reduction is respectively 36-40%, 31-36%, 28-32%, 24-28%, 19-24%, 15-20%, 12-16%, and the reduction decreases from the first pass to the seventh pass. The application effectively solves the slab center layering and edge cracking problems in the high-carbon martensitic stainless steel hot continuous rolling process, and greatly improves the production efficiency.

Description

Technical Field

[0001] This invention belongs to the field of stainless steel hot rolling production technology, specifically relating to a method for manufacturing high-carbon martensitic stainless steel hot-rolled coils. Background Technology

[0002] Martensitic stainless steel, especially high-carbon martensitic stainless steel with a carbon content greater than 0.40wt%, is mainly used to manufacture parts such as knives, scissors, and razors. Due to its high carbon content, it is easy to delaminate in the center of the billet thickness during hot rolling. At the same time, due to its poor thermoplasticity, it is also prone to edge crack defects, which reduces the yield and may cause equipment shutdown in severe cases.

[0003] Chinese patent application CN 113172089A proposes a "method for producing high-carbon martensitic stainless steel in a furnace coil rolling mill". It uses a two-stage heating furnace, which has a long heating time. Moreover, it uses a furnace coil rolling mill, which is not suitable for hot continuous rolling mill production, resulting in low production efficiency. Summary of the Invention

[0004] To address the technical problems existing in the prior art, this invention provides a method for manufacturing hot-rolled coils of high-carbon martensitic stainless steel, which uses a hot continuous rolling mill for production. This method greatly improves production efficiency while solving the problems of delamination and edge cracking in hot-rolled slabs.

[0005] The method for manufacturing high-carbon martensitic stainless steel hot-rolled coils of the present invention includes the following steps:

[0006] (1) Heating of billet

[0007] The billet is loaded into a walking beam furnace for heating. The furnace temperature of the first and second heating stages is controlled at 1280-1300℃, and the furnace temperature of the soaking stage is controlled at 1220-1250℃. The total heating time of the billet in the walking beam furnace is controlled at 180-230 min, and the holding time of the soaking stage is controlled at ≥50 min.

[0008] (2) Descaling

[0009] Ultra-high pressure water is used for descaling, with the pressure of the ultra-high pressure water controlled at 30-40 MPa. After descaling, the temperature of the center part of the end face of the billet is controlled at 1150-1200℃.

[0010] (3) Rough rolling

[0011] Before entering the roughing mill, the temperature of the center part of the end face of the billet after descaling is controlled at 1100-1160℃. The roughing mill adopts 5 passes, and the reduction rates of the 5 passes are controlled at 12-18%, 18-26%, 30-38%, 30-38%, and 35-40%, respectively. The final rolling temperature of the roughing mill is controlled at ≥1100℃.

[0012] (4) Finish rolling

[0013] The finishing rolling process uses 7 passes, and the reduction rates of the 7 passes are controlled as 36-40%, 31-36%, 28-32%, 24-28%, 19-24%, 15-20%, and 12-16%, respectively. Furthermore, the reduction rate decreases sequentially from the 1st pass to the 7th pass.

[0014] In one specific implementation method, in the above-mentioned manufacturing method of hot-rolled high-carbon martensitic stainless steel coil, the thickness of the cast billet is 130-220 mm, and in the rough rolling step, the thickness of the intermediate billet after rough rolling is controlled at 30-34 mm.

[0015] Furthermore, in the above-mentioned method for manufacturing hot-rolled high-carbon martensitic stainless steel coils, in the first pass of rough rolling, the value of k calculated based on the pre-roll thickness H, post-roll thickness h, roll linear speed v, and roll radius r according to the following formula (1) is controlled to be k≤3; in the second pass of rough rolling, the value of k calculated based on the pre-roll thickness H, post-roll thickness h, roll linear speed v, and roll radius r according to the following formula (1) is controlled to be k≤5:

[0016]

[0017] Furthermore, in the above-mentioned method for manufacturing high-carbon martensitic stainless steel hot-rolled coils, in the roughing step, the linear speed v of the upper roll is... 上 and the linear speed v of the lower roll 下 Both satisfy the following equations (2) and (3):

[0018]

[0019]

[0020] Furthermore, in the above-mentioned manufacturing method of hot-rolled high-carbon martensitic stainless steel coils, the finishing rolling temperature is controlled to be ≥1000℃.

[0021] Furthermore, in the above-mentioned method for manufacturing high-carbon martensitic stainless steel hot-rolled coils, a heat insulation cover, a hot rolling box, or edge heating is introduced between the rough rolling and finish rolling processes.

[0022] Furthermore, in the above-mentioned method for manufacturing high-carbon martensitic stainless steel hot-rolled coils, the high-carbon martensitic stainless steel is martensitic stainless steel with a carbon content greater than 0.40 wt%.

[0023] The manufacturing method of the high-carbon martensitic stainless steel hot-rolled coil of the present invention has the following advantages and beneficial effects:

[0024] This invention proposes a method for producing high-carbon martensitic stainless steel coils using a hot continuous rolling mill by controlling the furnace temperature of each section of the heating zone, the holding time of the soaking zone, the descaling pressure and the temperature of the billet after descaling, the reduction rate and rolling temperature during the rough rolling process, and the reduction rate and rolling temperature during the finish rolling process. This method effectively solves the problems of central delamination and edge cracking of the billet that occur during the hot continuous rolling of high-carbon martensitic stainless steel, and at the same time greatly improves production efficiency. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0026] The method for manufacturing high-carbon martensitic stainless steel hot-rolled coils of the present invention includes the following steps:

[0027] (1) Heating of billet

[0028] Billets with a thickness of 130–220 mm are loaded into a walking beam furnace. The furnace is divided into a preheating section, a first heating section, a second heating section, and a soaking section. The furnace temperature in the first and second heating sections is controlled at 1280–1300℃, and the furnace temperature in the soaking section is controlled at 1220–1250℃. The total heating time of the billet in the walking beam furnace is controlled at 180–230 min, and the holding time in the soaking section is controlled at ≥50 min.

[0029] (2) Descaling

[0030] Descaling is performed using ultra-high pressure water, with the water pressure controlled at 30–40 MPa. After descaling, the temperature of the center part of the billet end face is controlled at 1150–1200℃.

[0031] (3) Rough rolling

[0032] Before entering the roughing mill, the temperature of the center part of the end face of the billet after descaling is controlled at 1100-1160℃. The roughing mill adopts 5 passes, and the reduction rates of the 5 passes are controlled at 12-18%, 18-26%, 30-38%, 30-38%, and 35-40%, respectively. After the roughing mill is completed, the thickness of the intermediate billet is controlled at 30-34mm, and the final rolling temperature of the roughing mill is controlled at ≥1100℃.

[0033] Furthermore, in the first pass of roughing, the value of k calculated based on the pre-roll thickness H, post-roll thickness h, roll linear speed v, and roll radius r according to the following formula (1) is controlled to be k≤3; in the second pass of roughing, the value of k calculated based on the pre-roll thickness H, post-roll thickness h, roll linear speed v, and roll radius r according to the following formula (1) is controlled to be k≤5:

[0034]

[0035] Furthermore, in the roughing step, the linear speed v of the upper roll... 上 and the linear speed v of the lower roll 下 Both satisfy the following equations (2) and (3):

[0036]

[0037]

[0038] (4) Finish rolling

[0039] Between the roughing and finishing mills, insulation covers, hot coil boxes, or edge heating are used to minimize edge temperature drop. The finishing mill uses a 7-pass rolling process, with the reduction rates for the 7 passes controlled at 36–40%, 31–36%, 28–32%, 24–28%, 19–24%, 15–20%, and 12–16%, respectively. Furthermore, the reduction rate decreases sequentially from the 1st to the 7th pass.

[0040] In addition, during the finishing rolling process, the finishing rolling temperature is controlled to be ≥1000℃.

[0041] Furthermore, in the manufacturing method of the high-carbon martensitic stainless steel hot-rolled coil of the present invention, the high-carbon martensitic stainless steel is a martensitic stainless steel with a carbon content greater than 0.40 wt%.

[0042] The following describes the manufacturing method of the high-carbon martensitic stainless steel hot-rolled coil of the present invention with reference to specific embodiments.

[0043] Example 1

[0044] In the manufacturing method of high-carbon martensitic stainless steel hot-rolled coil in Example 1, the billet thickness is 200 mm, the target thickness of the finished product is 4.0 mm, the steel grade is 50Cr15MoV, and the width of the hot-rolled coil is 1240 mm. The specific implementation of the manufacturing method of high-carbon martensitic stainless steel hot-rolled coil in Example 1 is as follows:

[0045] (1) Heating of billet

[0046] The billet is loaded into a walking beam furnace for heating. The furnace temperature in the first and second heating stages is controlled at 1290℃, and the furnace temperature in the soaking stage is controlled at 1240℃. The total heating time of the billet in the walking beam furnace is controlled at 220 minutes, and the holding time in the soaking stage is controlled at 60 minutes.

[0047] (2) Descaling

[0048] Descaling is performed using ultra-high pressure water, with the water pressure controlled at 32 MPa. After descaling, the temperature of the center part of the billet end face is controlled at 1180℃.

[0049] (3) Rough rolling

[0050] After descaling, the temperature of the center portion of the billet end face is controlled at 1150℃ before entering the roughing mill. The roughing mill uses 5 passes, with a roll radius of 620mm. The final rolling temperature is controlled at 1120℃. The parameter values ​​for the 5 passes of the roughing mill are shown in Table 1 below:

[0051] Table 1. Parameters for each pass of roughing in Example 1

[0052]

[0053] (4) Finish rolling

[0054] Insulation covers and hot rolling boxes are placed between the roughing and finishing mills. The finishing mill adopts 7 passes, and the reduction rates of each pass are controlled at 36.3%, 33.3%, 30%, 25.5%, 22%, 17.5%, and 14.9%, respectively. The final rolling temperature of the finishing mill is controlled at 1030℃.

[0055] Based on actual production conditions, during the entire rolling process of producing 4.0mm thick 50Cr15MoV hot-rolled coils using the manufacturing method of high-carbon martensitic stainless steel hot-rolled coils in Example 1, the billet was free from delamination and edge cracks, and the total production cycle was significantly reduced, resulting in a substantial improvement in production efficiency.

[0056] Example 2

[0057] In the manufacturing method of high-carbon martensitic stainless steel hot-rolled coil in Example 2, the billet thickness is 160 mm, the target thickness of the finished product is 4.0 mm, the steel grade is 60Cr13, and the width of the hot-rolled coil is 1240 mm. The specific implementation of the manufacturing method of high-carbon martensitic stainless steel hot-rolled coil in Example 2 is as follows:

[0058] (1) Heating of billet

[0059] The billet is loaded into a walking beam furnace for heating. The furnace temperature in the first and second heating stages is controlled at 1280℃, and the furnace temperature in the soaking stage is controlled at 1240℃. The total heating time of the billet in the walking beam furnace is controlled at 210 minutes, and the holding time in the soaking stage is controlled at 55 minutes.

[0060] (2) Descaling

[0061] Descaling is performed using ultra-high pressure water, with the water pressure controlled at 32 MPa. After descaling, the temperature of the center part of the billet end face is controlled at 1180℃.

[0062] (3) Rough rolling

[0063] After descaling, the temperature of the center portion of the billet end face is controlled at 1150℃ before entering the roughing mill. The roughing mill uses 5 passes, with a roll radius of 620mm. The final rolling temperature is controlled at 1130℃. The parameter values ​​for the 5 passes of the roughing mill are shown in Table 1 below:

[0064] Table 2. Parameters for each pass of roughing in Example 2

[0065]

[0066] (4) Finish rolling

[0067] A heat insulation cover is placed between the roughing and finishing mills. The finishing mill adopts a 7-pass rolling process, with the reduction rate of each pass controlled at 36.67%, 32.63%, 28.13%, 25.00%, 20.29%, 16.36%, and 13.04%, respectively. The final rolling temperature of the finishing mill is controlled at 1020℃.

[0068] Based on actual production conditions, during the entire rolling process of producing 4.0mm thick 60Cr13 hot-rolled coils using the manufacturing method of high-carbon martensitic stainless steel hot-rolled coils in Example 2, the billet was free from delamination and edge cracks, and the total production cycle was significantly reduced, resulting in a substantial improvement in production efficiency.

[0069] In summary, the manufacturing method of high-carbon martensitic stainless steel hot-rolled coil of the present invention, by controlling the furnace temperature of each section of the heating zone and the holding time of the soaking zone, the descaling pressure and the temperature of the billet after descaling, the reduction rate and rolling temperature of the rough rolling process, and the reduction rate and rolling temperature of the finish rolling process, proposes a method for producing high-carbon martensitic stainless steel coil using a hot continuous rolling mill. This method effectively solves the problems of central delamination and edge cracking of the billet that occur during the hot continuous rolling of high-carbon martensitic stainless steel, and at the same time greatly improves production efficiency.

[0070] It should be noted that, in this document, the term "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device.

[0071] It should also be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the present invention.

Claims

1. A method for manufacturing a hot-rolled coil of high-carbon martensitic stainless steel, characterized in that, Production using a hot strip mill includes the following steps: (1) Heating of the billet The billet is loaded into a walking beam furnace for heating. The furnace temperature of the first and second heating stages is controlled at 1280~1300℃, and the furnace temperature of the soaking zone is controlled at 1220~1250℃. The total heating time of the billet in the walking beam furnace is controlled at 180~230min, and the holding time of the soaking zone is controlled at ≥50min. (2) Descaling Ultra-high pressure water is used for descaling, with the pressure of the ultra-high pressure water controlled at 30~40MPa. After descaling, the temperature of the center part of the end face of the billet is controlled at 1150~1200℃. (3) Rough rolling Before entering the roughing mill, the temperature of the center part of the end face of the billet after descaling is controlled at 1100~1160℃. The roughing mill adopts 5 passes, and the reduction rate of the 5 passes is controlled at 12~18%, 18~26%, 30~38%, 30~38%, and 35~40% respectively. The final rolling temperature of the roughing mill is controlled at ≥1100℃. (4) Finish rolling The finishing mill adopts a 7-pass rolling process. The reduction rates of the 7 passes are controlled as 36~40%, 31~36%, 28~32%, 24~28%, 19~24%, 15~20%, and 12~16%, respectively. Furthermore, the reduction rate decreases sequentially from the 1st pass to the 7th pass. In the first pass of roughing, the value of k calculated according to the following formula (1) based on the pre-roll thickness H, post-roll thickness h, roll linear speed v, and roll radius r is controlled to be k≤3; in the second pass of roughing, the value of k calculated according to the following formula (1) based on the pre-roll thickness H, post-roll thickness h, roll linear speed v, and roll radius r is controlled to be k≤5: （1）。 2. The method for manufacturing high-carbon martensitic stainless steel hot-rolled coils as described in claim 1, characterized in that, The thickness of the cast billet is 130~220mm. In the rough rolling step, the thickness of the intermediate billet is controlled at 30~34mm after rough rolling.

3. The method for manufacturing high-carbon martensitic stainless steel hot-rolled coils as described in claim 1, characterized in that, In the roughing process, the linear speed of the upper rolls and the linear speed of the lower roll Both satisfy the following equations (2) and (3): ≤3% （2） ≤3% （3）。 4. The method for manufacturing high-carbon martensitic stainless steel hot-rolled coils as described in claim 1, characterized in that, In the finishing rolling process, the finishing rolling temperature is controlled to be ≥1000℃.

5. The method for manufacturing high-carbon martensitic stainless steel hot-rolled coils as described in claim 1, characterized in that, Insulation covers, hot rolling boxes, or edge heating are installed between roughing and finishing rolling.

6. The method for manufacturing high-carbon martensitic stainless steel hot-rolled coils as described in any one of claims 1 to 5, characterized in that, The high-carbon martensitic stainless steel is a martensitic stainless steel with a carbon content greater than 0.40 wt%.

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