Stable welding and annealing through plate production process based on head and tail variable thickness rolling

Abstract

The invention relates to the technical field of cold rolling, and particularly discloses a stable welding and annealing through plate production process based on head and tail variable-thickness rolling, which comprises the following steps of: transporting a steel coil subjected to head and tail variable-thickness rolling to a next working procedure for uncoiling, and welding tail strip steel and forward strip steel; after the tail strip steel is welded with the forward strip steel, continuously operating until the strip head is welded with the backward strip steel; in the uncoiling and welding process of the strip steel, the rolling length L1 of the head strip steel and the rolling length L2 of the tail strip steel are changed to different degrees under the influence of cutting of the head strip steel and the tail strip steel; the thickness difference between the thickness H4 of the forward strip steel and the thickness H0 of the original strip steel of the thick-specification strip steel is large, the running speed of the forward strip steel is controlled to be v3, and the strip steel with the qualified thickness H0 is produced; the thickness of the head and the tail of the chilled strip steel is precisely designed through variable-thickness rolling of the rolling mill, the thickness transition difference is reduced or even eliminated, thickness transition coils are reduced, the welding quality is improved, and the limit thickness specification capable of being welded by the narrow lap welding machine is greatly expanded.

Description

Technical Field

[0001] The invention relates to the technical field of cold rolling, and in particular to a stable welding and annealing plate production process based on head-to-tail variable thickness rolling. Background Art

[0002] The welding machine is an important equipment of the continuous annealing / continuous hot-dip galvanizing unit. It connects the front and rear strips together by welding to meet the uninterrupted continuous production requirements of the production line.

[0003] Narrow lap welders are widely used in continuous annealing / continuous hot-dip galvanizing units due to their high cost-effectiveness. However, with the expansion of specifications and strengths, narrow lap welders are increasingly unable to meet the welding requirements of extremely thick specifications and high-strength strip steel. For example, the first-time welding pass rate of strip steel with specifications above 2.0mm and strength above 590MPa is low, and there are many problems such as weld cracking. These problems restrict the units equipped with narrow lap welding from further expanding their varieties and specifications. In order to produce thick specifications and high-strength steel, many units choose to configure more expensive laser welders.

[0004] Research has shown that factors that affect the welding quality of narrow lap welders include not only welding parameters such as welding current, welding speed, and welding wheel pressure, but also the material of the substrate and the thickness difference of the substrate.

[0005] In order to solve the problem of welding thick high-strength steel on narrow lap welding machines, current research mainly focuses on optimizing welding parameters, using ordinary plate + high-strength steel insert welding, and increasing transition materials to reduce thickness differences. Therefore, it is necessary to design a stable welding and annealing plate production process based on head-to-tail variable thickness rolling. The technical problem to be solved is that it is difficult and has a low success rate to weld thick high-strength steel on narrow lap welding machines, which leads to difficulties in expanding specifications and a high production accident rate for extreme specifications of thickness and strength. Summary of the invention

[0006] In view of the problems existing in the prior art, the purpose of the present invention is to provide a stable welding and annealing plate production process based on head-to-tail variable thickness rolling. Without adding transition material, the head and tail thickness of the cold-hardened strip is accurately designed through variable thickness rolling of the rolling mill, which is convenient for reducing or even eliminating the thickness transition difference during the welding of the cold-hardened coil in the continuous annealing / galvanizing process, improving the welding quality, and designing a reasonable annealing speed system to ensure stable plate passing of the strip in the annealing furnace.

[0007] The technical solution adopted by the present invention to solve the technical problem is: a stable welding and annealing plate production process based on head-to-tail variable thickness rolling, comprising the following steps:

[0008] S1, thick strip with thickness H0 and width B0, when narrow lap welding is arranged, the front strip thickness H4, width B4 and the rear strip thickness H3, width B3, accordingly design the head thickness H1 and tail thickness H2 of the thick strip;

[0009] S2. When the rolling mill is in production, the head strip is rolled to a thickness of H1 and a rolling length of L1 as required, and the tail strip is rolled to a thickness of H2 and a rolling length of L2, and the data information of H1, L1, H2, L2, H0, and L0 is transmitted to the next process through the MES system;

[0010] S3, the steel coils that have been rolled with variable thickness at the head and tail are transported to the next process for uncoiling, and the tail strip is welded with the front strip;

[0011] S4, after the tail strip is welded with the front strip, the strip continues to run until the head of the strip is welded with the rear strip;

[0012] S5. During the uncoiling and welding process of the strip, the length of the head strip L1 and the length of the tail strip L2 will change to varying degrees due to the removal of the head and tail strips.

[0013] S6, the thickness difference between the front strip thickness H4 and the original strip thickness H0 of the thick-gauge strip is large, and the running speed of the front strip is controlled to v3;

[0014] S7. When the strip is stably passed through the plate and is coiled and cut at the exit, the exit flying shear will completely cut off the head length L1' and the tail length L2' of the variable thickness rolling area of ​​the strip to produce a strip with a qualified thickness H0.

[0015] Specifically, the specification parameters of the thick-gauge strip steel in step S1 are (H1-H3) / H3≤10%, (H2-H4) / H4≤10%, (H0-H1) / H0≤20%, (H0-H2) / H0≤20%, preferably H1=H3, H2=H4.

[0016] Specifically, L0 in step S2 is the normal thickness rolling length of the strip steel, usually L1≤20m, L2≤20m.

[0017] Specifically, the welding of the tail of the strip with the preceding strip in step S3, i.e., the welding of the tail strip with a thickness of H2 with the preceding strip with a thickness of H4, is performed because the thickness H2 of the tail of the strip is significantly lower than the thickness H0 of the original strip, and the thickness difference between the thickness H2 of the tail of the strip and the thickness H4 of the preceding strip is small or even nonexistent, and the success rate of narrow lap welding is higher than that of direct welding of the thickness H4 of the preceding strip with the thickness H0 of the original strip.

[0018] Specifically, the welding of the strip head and the subsequent strip in step S4, i.e., the welding of the strip head strip with a thickness of H1 and the subsequent strip with a thickness of H3, similarly, because the strip head thickness H1 is significantly lower than the original strip thickness H0, and the thickness difference with the subsequent strip thickness H3 is small or even no thickness difference, the narrow lap welding has a higher success rate than the direct welding of the subsequent strip thickness H3 and the original strip thickness H0.

[0019] Specifically, the length changes of the head strip rolling length L1 and the tail strip rolling length L2 in step S5 are collected by the PLC system and transmitted to the MES system. The MES system corrects the length of the variable thickness rolling area of ​​the strip to the head length L1' and the tail length L2' for reference in the subsequent finished product coiling and slitting process.

[0020] Specifically, the running speed of the forward strip in step S6 is v3, and the speed in the furnace is controlled as follows during the production process:

[0021] (1) If (H0*B0-H4*B4) / (H4*B4)≤30%, the furnace speed still runs at the set speed v3 of the forward strip, and there is no need to reduce the speed;

[0022] (2) If 30% ≤ (H0*B0-H4*B4) / (H4*B4) ≤ 40%, reduce the furnace speed to v3*80%;

[0023] (3) If (H0*B0-H4*B4) / (H4*B4)≥40%, reduce the furnace speed to v3*40%.

[0024] The present invention has the following beneficial effects:

[0025] The stable welding and annealing plate production process based on head-to-tail variable thickness rolling designed in the present invention expands the production limit of thick specifications and high-strength levels of narrow lap welding machines, and improves the production capacity and profitability of the unit.

[0026] The stable welding and annealing plate production process based on head-to-tail variable thickness rolling designed by the present invention can achieve large-span connection of strip steel specifications without adding transition materials, thereby reducing the production cost of extreme specifications.

[0027] The invention designs a stable welding and annealing plate production process based on head-to-tail variable thickness rolling, and a consistent design of the acid rolling, welding and annealing manufacturing processes, thereby ensuring the stability of the entire production process and reducing the accident rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flow chart of the stable welding and annealing plate production process based on head-to-tail variable thickness rolling.

[0029] Figure 2It is a schematic diagram of welding of variable thickness rolled strip steel at the head and tail.

[0030] In the figure: 1-front strip (thickness H4); 2-tail of variable thickness rolled strip (thickness H2); 3-normal rolled strip (thickness H0, length L0); 4-head of variable thickness rolled strip (thickness H1); 5-rear strip (thickness H3); 6-front strip weld; 7-tail variable thickness rolled length L2; 8-head variable thickness rolled length L1; 9-rear strip weld. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely further describe the technical solutions in the embodiments of the present invention. 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.

[0032] like Figure 1-Figure 2 As shown, a stable welding and annealing plate production process based on head-to-tail variable thickness rolling includes the following steps:

[0033] 1. For thick-gauge strip steel with a thickness of H0 and a width of B0, when narrow lap welding is arranged, the thickness of the front strip steel is H4 and the width is B4, and the thickness of the rear strip steel is H3 and the width is B3. The head thickness H1 and the tail thickness H2 of the thick-gauge strip steel are designed accordingly; the specification parameters of the thick-gauge strip steel are (H1-H3) / H3≤10%, (H2-H4) / H4≤10%, (H0-H1) / H0≤20%, (H0-H2) / H0≤20%, preferably H1=H3, H2=H4.

[0034] 2. When the rolling mill is in production, the head strip thickness is rolled to H1 and the rolling length is L1, and the tail strip thickness is rolled to H2 and the rolling length is L2 as required, and the H1, L1, H2, L2, H0, L0 data information is transmitted to the next process through the MES system; L0 is the normal thickness rolling length of the strip, usually L1≤20m, L2≤20m.

[0035] 3. The steel coils that have been rolled with variable thickness at the head and tail are transported to the next process for uncoiling, and the tail strip is welded with the front strip, that is, the tail strip with a thickness of H2 is welded with the front strip with a thickness of H4. Because the thickness H2 of the tail strip is greatly reduced compared with the thickness H0 of the original strip, and the thickness difference between the thickness H2 of the tail strip and the thickness H4 of the front strip is small or even no thickness difference, the narrow lap welding has a higher success rate and better quality than the direct welding of the front strip thickness H4 and the original strip thickness H0.

[0036] 4. After the tail strip is welded with the preceding strip, the strip continues to run until the head of the strip is welded with the following strip, that is, the head strip with a thickness of H1 is welded with the following strip with a thickness of H3. Similarly, because the thickness of the head strip H1 is significantly lower than the thickness of the original strip H0, and the thickness difference with the thickness of the following strip H3 is small, or even no thickness difference, the narrow lap welding has a higher success rate and better quality than the direct welding of the thickness of the following strip H3 with the thickness of the original strip H0.

[0037] 5. During the uncoiling and welding process of the strip, the length of the head strip rolling length L1 and the tail strip rolling length L2 will change to varying degrees due to the cutting of the head and tail strips. The data is collected through the PLC system and transmitted to the MES system. The MES system corrects the length of the variable thickness rolling area of ​​the strip to the head length L1' and the tail length L2', which is used as a reference for cutting in the subsequent finished product coiling and slitting process.

[0038] 6. The thickness difference between the front strip H4 and the original thick strip H0 is large, and the cross-sectional difference between the front and rear strips is too large. In order to avoid excessive thermal shock to the furnace rollers caused by the rear thick strip, the strip deviates in the furnace, and even scrapes and breaks, the running speed of the front strip needs to be controlled to v3; the speed control in the furnace during the production process is as follows:

[0039] (1) If (H0*B0-H4*B4) / (H4*B4)≤30%, the furnace speed still runs at the set speed v3 of the forward strip, and there is no need to reduce the speed;

[0040] (2) If 30% ≤ (H0*B0-H4*B4) / (H4*B4) ≤ 40%, reduce the furnace speed to v3*80%;

[0041] (3) If (H0*B0-H4*B4) / (H4*B4)≥40%, reduce the furnace speed to v3*40%.

[0042] 7. When the strip steel runs stably through the plate to the exit for coiling and slitting, the exit flying shear will completely cut off the head length L1' and the tail length L2' of the variable thickness rolling area of ​​the strip steel to ensure that the strip steel delivered to the user is of qualified thickness H0.

[0043] The leading strip / the following strip can also be rolled with variable thickness at the head and tail, for example, the leading strip can be rolled thicker at the tail and thicker at the head, so as to further expand the thickness transition specification span.

[0044] Example: Figure 2As shown in the figure, a user ordered high-strength steel of grade 780DHD with thickness H0=2.5mm and width B0=1250mm. There was only a transition piece of grade 780DHD with thickness 2.1mm and width 1100mm available on site. The conventional production process required the preparation of DX51D general plate transition materials of the same specification with thickness 2.5mm and thickness 2.3mm for flower-cut welding.

[0045] By adopting the production process of the present invention, the actual orders of the same steel grade 780DHD with a thickness of 2.1mm and a width of 1100mm can be used as the front and rear strips, and the target material with a thickness of 2.5mm can be rolled with variable thickness at the head and tail to achieve stable welding, plate passing and qualified delivery.

[0046] During rolling mill production, the head 20m of the target material with a thickness of 2.5mm is rolled to a thickness of 2.1mm, and then rolled to a normal thickness of 2.5mm. The tail 20m is rolled to a thickness of 2.1mm again, and the data information of the head 20m thickness of 2.1mm, the tail 20m thickness of 2.1mm, and the middle normal thickness of 2.5mm and length of 780m is transmitted to the next process hot-dip galvanizing unit through the MES system.

[0047] The steel coil with variable thickness at the head and tail is transported to the next process hot-dip galvanizing unit for uncoiling, and the tail is welded with the 2.1mm thick solid single strip of the same steel grade in front, that is, the 2.1mm thick tail strip is welded with the 2.1mm thick front strip. The welding thickness of the same steel grade is reduced to 2.1mm, and there is no thickness difference, which has a higher welding success rate and better quality.

[0048] After the tail of the strip is welded with the preceding strip, it continues to run at a speed of 120mpm until the head of the strip is also welded with the succeeding strip.

[0049] During the uncoiling and welding process, the strip is affected by the head and tail cutting. The data is collected through the PLC system and the length of the variable thickness rolling area of ​​the strip is corrected to 15m at the tail and 14m at the head.

[0050] The cross-sectional difference between the forward strip and the target strip is (2.5*1250-2.1*1100) / 2.1*1100=35%, which is in the range of [30%, 40%]. The speed of the thick target material in the furnace is reduced to 80% of the set speed of the forward strip, that is, it runs at 96mpm.

[0051] When the strip steel runs stably through the plate to the exit for coiling and slitting, the exit flying shear will cut off the tail length of 15m and the head length of 14m in the variable thickness rolling area of ​​the strip steel to ensure that the strip steel delivered to the user is of qualified thickness of 2.5mm.

[0052] The present invention is not limited to the above-mentioned implementation modes, and anyone should be aware of the structural changes made under the enlightenment of the present invention, and all those having the same or similar technical solutions as the present invention fall within the protection scope of the present invention.

[0053] The techniques, shapes, and structural parts not described in detail in the present invention are all well-known techniques.

Claims

1. A stable welding and annealing plate production process based on head-to-tail variable thickness rolling, characterized in that: The following steps are involved: S1, thick strip with thickness H0 and width B0, when narrow lap welding is arranged, the front strip thickness H4, width B4 and the rear strip thickness H3, width B3, accordingly design the head thickness H1 and tail thickness H2 of the thick strip; S2. When the rolling mill is in production, the head strip is rolled to a thickness of H1 and a rolling length of L1 as required, and the tail strip is rolled to a thickness of H2 and a rolling length of L2, and the data information of H1, L1, H2, L2, H0, and L0 is transmitted to the next process through the MES system; S3, the steel coils that have been rolled with variable thickness at the head and tail are transported to the next process for uncoiling, and the tail strip is welded with the front strip; S4, after the tail strip is welded with the front strip, the strip continues to run until the head of the strip is welded with the rear strip; S5. During the uncoiling and welding process of the strip, the length of the head strip L1 and the length of the tail strip L2 will change to varying degrees due to the removal of the head and tail strips. S6, the thickness difference between the front strip thickness H4 and the original strip thickness H0 of the thick-gauge strip is large, and the running speed of the front strip is controlled to v3; S7. When the strip is stably passed through the plate and is coiled and cut at the exit, the exit flying shear will completely cut off the head length L1' and the tail length L2' of the variable thickness rolling area of ​​the strip to produce a strip with a qualified thickness H0.

2. The stable welding and annealing plate production process based on head-to-tail variable thickness rolling according to claim 1 is characterized in that: The specification parameters of the thick-gauge strip steel in step S1 are (H1-H3) / H3≤10%, (H2-H4) / H4≤10%, (H0-H1) / H0≤20%, (H0-H2) / H0≤20%, preferably H1=H3, H2=H4.

3. The stable welding and annealing plate production process based on head-to-tail variable thickness rolling according to claim 1 is characterized in that: L0 in step S2 is the normal thickness rolling length of the strip steel, usually L1≤20m, L2≤20m.

4. The stable welding and annealing plate production process based on head-to-tail variable thickness rolling according to claim 1 is characterized in that: The welding of the tail of the strip with the preceding strip in step S3, i.e., the welding of the tail strip with a thickness of H2 with the preceding strip with a thickness of H4, is performed because the thickness H2 of the tail of the strip is significantly lower than the thickness H0 of the original strip, and the thickness difference between the thickness H2 of the tail of the strip and the thickness H4 of the preceding strip is small or even nonexistent, and the narrow lap welding has a higher success rate than the direct welding of the thickness H4 of the preceding strip with the thickness H0 of the original strip.

5. The stable welding and annealing plate production process based on head-to-tail variable thickness rolling according to claim 1 is characterized in that: The welding of the strip head and the subsequent strip in step S4 is the welding of the strip head with a thickness of H1 and the subsequent strip with a thickness of H3. Similarly, because the strip head thickness H1 is significantly lower than the original strip thickness H0, and the thickness difference with the subsequent strip thickness H3 is small or even no thickness difference, the narrow lap welding has a higher success rate than the direct welding of the subsequent strip thickness H3 and the original strip thickness H0.

6. The stable welding and annealing plate production process based on head-to-tail variable thickness rolling according to claim 1 is characterized in that: The length changes of the head strip rolling length L1 and the tail strip rolling length L2 in step S5 are collected by the PLC system and transmitted to the MES system. The MES system corrects the length of the variable thickness rolling area of ​​the strip to the head length L1' and the tail length L2' for reference in the subsequent finished product coiling and slitting process.

7. The stable welding and annealing plate production process based on head-to-tail variable thickness rolling according to claim 1 is characterized in that: The running speed of the forward strip in step S6 is v3. The speed control in the furnace during production is as follows: (1) If (H0*B0-H4*B4) / (H4*B4)≤30%, the furnace speed still runs at the set speed v3 of the forward strip, and there is no need to reduce the speed; (2) If 30% ≤ (H0*B0-H4*B4) / (H4*B4) ≤ 40%, reduce the furnace speed to v3*80%; (3) If (H0*B0-H4*B4) / (H4*B4)≥40%, reduce the furnace speed to v3*40%.

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