A hot continuous rolling process rolling method for a stainless steel composite plate

Abstract

The present invention discloses a hot rolling process for stainless steel composite plates, which belongs to the field of hot rolling technology and includes: S1, selecting materials for a base plate and a cover plate, and compounding them to obtain a slab; S2, heating in a heating furnace; S3, removing primary iron oxide with high-pressure water; S4, rough rolling; S5, cutting; S6, finishing rolling; S7, laminar cooling of the strip; S8, transporting the double-sided composite plate coil after finishing rolling to a coiling mechanism via a transmission roller for coiling. This application formulates a reasonable production process by controlling the heating temperature, heating time, rough rolling passes, finishing cutting fly shear head length, finishing rolling temperature, roller shape, laminar cooling rate, etc. It solves the problem that brittle oxides are easily generated at the interface during hot rolling, which affects the composite effect and bonding strength, and cracking, delamination, bubbles, etc. are easily generated during cold bending.

Description

Technical Field

[0001] The invention belongs to the technical field of hot continuous rolling, and in particular relates to a hot continuous rolling process method for a stainless steel composite plate. Background Art

[0002] In recent years, as people's demands for materials have become increasingly stringent, traditional single-metal or alloy materials have become inadequate to meet the demands of modern society. The use of some precious metals and scarce materials is limited by natural resources. New stainless steel composite plate materials offer excellent surface quality and mechanical properties, along with the superior mechanical properties and machinability of carbon steel. They also possess excellent corrosion, fire, and heat resistance, resist scaling, and maintain strength at high temperatures. As a product that reduces the use of precious metals and improves resource utilization, they are widely used in construction, metallurgy, shipbuilding, petroleum, chemical engineering, water conservancy and power generation, and food industries. Their low production cost and high performance and surface quality have earned them widespread recognition. As a resource-saving product, stainless steel composite plate reduces the consumption of precious metals, significantly lowering project costs and achieving a perfect combination of low cost and high performance, resulting in significant social benefits. Therefore, the question of how to produce new stainless steel composite materials using alloy precious metals at low cost and low dosage has become a key research and development direction.

[0003] Currently, three methods are used to produce stainless steel composite plates: explosive rolling, explosive rolling, and rolling. Each method has its own advantages and disadvantages due to its different preparation processes. The explosive rolling method is typically used in remote outdoor locations to produce composite plates. While it requires minimal investment, the production process uses explosives, which is significantly affected by weather conditions, presents safety concerns, and contributes to environmental pollution and low production efficiency. The explosive rolling method, however, suffers from the limitations of small plate widths, resulting in limited product quality and dimensional accuracy. Due to the constraints of external conditions, output and productivity are also relatively low. Rolling methods are categorized into cold rolling and hot rolling. Cold rolling utilizes atmospheric pressure to bond materials, resulting in higher costs and better material stability, but also has certain dimensional limitations. Hot rolling, on the other hand, allows for continuous, large-scale production of stainless steel composite plates, is not subject to weather restrictions, offers high production efficiency and low costs, and offers large product widths, allowing for processing of larger materials while minimizing contamination from non-metallic impurities. Hot rolling also allows for various processing techniques, such as hot pressing, cold bending, cutting, and welding, and exhibits excellent processability.

[0004] Hot-rolled stainless steel composite plates are composite materials with carbon steel as the substrate and stainless steel as the cladding plate. Hot rolling is the process of processing the composite plate material using a hot rolling mill according to certain heating and rolling temperatures. Its main feature is that carbon steel and stainless steel form a strong metallurgical bond. However, during the hot rolling process, brittle oxides are easily generated at the interface, affecting the composite effect and bonding strength, and cracking and delamination are prone to occur during cold bending. Therefore, it is particularly important to develop a suitable hot rolling process and find the appropriate rolling temperature and reduction rate to solve problems such as thickness uniformity and bonding strength of hot rolling. For domestic steel companies, there are still some key technologies that need to be broken through in the production process of hot-rolled stainless steel composite plates. Summary of the Invention

[0005] The present invention aims to solve the technical problems existing in the known technology and provides a hot continuous rolling process for stainless steel composite plates.

[0006] The object of the present invention is to provide a hot continuous rolling process for a stainless steel composite plate, comprising:

[0007] S1. Select materials for the substrate and cover plate and compound them to obtain a slab; the substrate is one of Q235B, Q355B, and 65Mn, and the cover plate is 304 stainless steel; the composite structure from bottom to top is: first substrate, first cover plate, second cover plate, and second substrate;

[0008] S2. Heating in the heating furnace: The slab is heated to the rolling temperature before being taken out of the furnace. The furnace time of Q235B composite slab is not less than 270 minutes, the furnace time of Q355B composite slab is not less than 300 minutes, and the furnace time of 65Mn composite slab is not less than 300 minutes. The high temperature section time is not less than 90 minutes. The heating temperature is not less than 1230℃. The temperature difference between the rough rolling and final polishing steel and the plate temperature is ±30℃. The average temperature of the rough rolling and final polishing steel between furnaces is within 25℃. The furnace adopts a weak oxidizing atmosphere.

[0009] S3. Use high-pressure water to remove primary iron oxide;

[0010] S4. Rough rolling: After heating, the qualified slab is rough rolled in 5 passes; the single-row header for rough descaling is opened, and descaling is performed in passes 1 and 5. The tapping temperature of the final rough rolling pass is 1120±20℃, and the intermediate slab thickness is 49cm;

[0011] S5, cutting head;

[0012] S6, finishing rolling, finished product thickness <9.0mm, using seven stands; finished product thickness ≥9.0, using stands 2 and 5; in terms of roll profile configuration, the work rolls adopt a concave roll profile, with a concave of 0.12mm during rolling; fine descaling uses a single row of scales, and the cooling water and reverse water spray between each stand are turned off; the finishing rolling temperature is: Q235B composite slab is controlled at 870±20℃; Q355B composite slab is controlled at 860±20℃; 65Mn composite slab is controlled at 860±20℃;

[0013] S7, strip laminar cooling, using cooling water for forced cooling, no cooling of the edge, and rapid cooling of the front section area;

[0014] S8. The double-sided composite plate coil that has undergone fine rolling is transported to a coiling mechanism via a transfer roller for coiling.

[0015] Preferably, in S1 , the thickness of the first substrate is 85 mm, the thickness of the first cover plate is 16 mm, the thickness of the second cover plate is 16 mm, and the thickness of the second substrate is 85 mm.

[0016] Preferably, S5 specifically includes: adjusting the cutting length of the first 20 pieces of steel to 100 mm and performing cutting.

[0017] Preferably, in S7, the cooling rate is controlled as follows: the front-stage cooling rate V1 is 19.20°C / S, and the rear-stage cooling rate V2 is 12.30°C / S.

[0018] Preferably, in S8, the coiling temperature is: Q235B composite slab is controlled at 680±20°C, Q355B composite slab is controlled at 630±20°C, and 65Mn composite slab is controlled at 630±20°C.

[0019] Preferably, it also includes S9, inspection and storage, and the coiled plate coils are numbered, bundled, and stored.

[0020] The advantages and positive effects of the present invention are:

[0021] This application develops a reasonable production process by controlling the heating temperature, heating time, rough rolling passes, finishing shear head length, finishing rolling temperature, roll shape, laminar flow and cooling rate. The application also studies the impact of different production processes on the microstructure and performance, and addresses issues such as the formation of brittle oxides at the interface during hot rolling, which affects the composite effect and bonding strength, and the occurrence of cracking, delamination, and bubbles during cold bending. The optimization is achieved to successfully roll stainless steel composite plates. DETAILED DESCRIPTION

[0022] In order to make the above-mentioned purpose, design control system and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0023] The technical solution of the present invention is:

[0024] A hot continuous rolling process for stainless steel composite plates comprises the following process steps: slab → slab surface inspection and cleaning, slab heating → high-pressure water descaling → rough rolling → flying shear head → finishing rolling → coiling → quality and performance inspection → packaging and marking → warehousing → coiling.

[0025] The object of the present invention is achieved like this:

[0026] Step 1: Determine the heating temperature and heating time: The heating temperature not only affects the forming process of the stainless steel composite plate, but also affects the microstructure, strength and toughness of the steel layer, and interface bonding performance.

[0027] Step 2: Determine the rolling temperature: When the temperature is too low, the heat dissipation rate of the plate is too fast, resulting in the inability to complete the composite. Only by ensuring the temperature can a better composite degree be achieved. It should be noted that when the temperature is too high, while strengthening the bonding strength between metals, it will also form certain unnecessary chemical reactions, which will have a certain adverse effect on the plate coil and will also be a certain waste of cost.

[0028] Step 3: Determine the reduction system: The bonding strength of the composite board is directly dependent on the reduction rate. If the reduction rate is too low, the bonding strength will be insufficient and the board's functional requirements will not be met. If the reduction rate is too high, the bonding surface of the board will be uneven over a large area, affecting the surface properties of the coil.

[0029] Step 4: Descaling process: By reducing the number of descaling passes in the initial stage of rough rolling, the initial plate shape and thickness of the rolling are determined; then, the surface quality of the steel plate is determined by descaling through finishing rolling;

[0030] Step 5: Controlled cooling process: By controlling the laminar cooling mode, flow rate and speed, the coil cooling is controlled to obtain the required coil performance.

[0031] In order to further illustrate the technical solution of the present invention, the following is an explanation with specific embodiments; the specific steps are as follows:

[0032] First, the base plate is selected as Q235B, Q355B, 65Mn, and the cover plate is 304 stainless steel; the composite method is: base plate (85mm) + 304 stainless steel (16mm) + 304 stainless steel (16mm) + base plate (85mm);

[0033] Step 1: Heating in the heating furnace: According to the heating system, the slab is heated to the rolling temperature and then taken out of the furnace. To ensure the ductility of the base plate material and the cladding plate material is consistent, the furnace time of Q235BFH is required to be ≥270min, the furnace time of Q355B FH is required to be ≥300min, and the furnace time of 65Mn is required to be ≥300min; the high temperature section time is required to be ≥90min; the heating temperature is required to be ≥1230℃; the temperature of the rough rolling final polishing steel is within ±30℃ of the same plate, and the average temperature of the rough rolling final polishing steel between furnaces is within 25℃; the furnace adopts a weak oxidizing atmosphere.

[0034] Step 2: Descaling with high-pressure water after the furnace to remove primary iron oxide.

[0035] Step 3: Rough rolling: After heating, the qualified slab is rough rolled in five passes. The single-row header for rough descaling is opened, and descaling is performed in passes 1 and 5. The tapping temperature of the final rough rolling pass is 1120±20°C. The intermediate slab thickness is 49cm.

[0036] Step 4: Cut the head. Adjust the cutting length of 20 pieces of steel to 100mm before rolling.

[0037] In order to prevent the intermediate billet from generating temperature gradient, reduce the temperature drop of the intermediate billet and prevent the weld cracking, the post-furnace descaling, rough descaling and fine descaling adopt the edge shielding method.

[0038] Step 5, finishing rolling, finished product thickness <9.0mm, adopt seven-stand rolling, finished product thickness ≥9.0, adopt throwing 2nd and 5th stands rolling; in the configuration of roller curve, the working roll adopts concave roller profile, concave 0.12mm for rolling; fine descaling adopts single row descaling, and the cooling water and reverse spray water between each stand are turned off; the finishing rolling temperature of Q235BFH is controlled at 870±20℃; Q355BFH is controlled at 860±20℃, and 65MnFH is controlled at 860±20℃.

[0039] Step 6: The strip is cooled in laminar flow, with forced cooling by cooling water. The edge is not cooled, and the cooling method adopts rapid cooling in the front section. The cooling rate control is: V1 is 19.20℃ / S, and V2 is 12.30℃ / S.

[0040] Step 7: The finished double-sided composite sheet coil is transported to the coiling mechanism via conveyor rollers for winding. To ensure substrate performance, the coiling temperature is controlled according to the requirements of the substrate material: Q235BFH at 680±20°C, Q355BFH at 630±20°C, and 65MnFH at 630±20°C.

[0041] Step 8: Inspection and storage. The coiled sheets are numbered, bundled, and stored. According to the sampling requirements, the third sample of the same batch is taken, and the sample size and surface quality are checked. The physical properties of the sample are tested to ensure that the quality meets the national standards.

[0042] 1 The above scheme is applicable to the process control and quality management of the hot continuous rolling method of stainless steel composite plates;

[0043] 2. Slab specifications: 230×900~1600×L mm;

[0044] 3. Coil specifications: 3.0-16.0×900~1600×C mm;

[0045] 4. Coil size tolerance:

[0046] The size, shape, weight and allowable deviation of the coil shall comply with the requirements of GB / T8165-2008.

[0047] 5. Product process flow:

[0048] Slab → Surface inspection and cleaning of slab, Slab heating → High-pressure water descaling → Rough rolling → Head cropping and flying shearing → Finishing rolling → Coiling → Quality and performance inspection → Packaging and marking → Storage → Coil.

[0049] 6 Mechanical properties:

[0050] The mechanical properties of stainless steel composite plates should comply with the requirements of the corresponding standards of the base materials.

[0051] Table 1 shows the cold bending test

[0052]

[0053] 7. Process requirements:

[0054] 7.1 Heating system:

[0055] Table 2 shows the heating system

[0056]

[0057] 7.2 Temperature system:

[0058] Table 3 is the temperature system table

[0059]

[0060] 7.3 Before production, carefully check the PDI parameters, measure the width and thickness, calibrate the instrument accuracy, and ensure that the dimensional tolerance is within the order requirements.

[0061] 7.4 The rough rolling operator may reduce the rolling speed appropriately according to the rolling state and the degree of slippage. The reference values are: first pass: 1.2m / s, second pass, 2.0m / s, speed increment 0.5m / s, fifth pass: 4.0m / s.

[0062] 7.5 Arrange the rolling plan reasonably, arrange sampling according to specifications and furnaces, and ensure normal plate shape.

[0063] 7.6 Descaling system: Depending on the descaling status, coarse descaling is put into use in a single row, descaling on the roughing mill is put into use in odd passes, and fine descaling is put into use in a single row. During descaling, the edges are shielded, and the cooling water and reverse spray water between the stands are turned off.

[0064] 7.7 Insulation cover: Except for the first 5 groups of insulation covers, the full length and number of insulation covers are used at other times; the thickness of the intermediate billet is 49mm.

[0065] 7.8 Flying shear system: When flying shearing, the cutting depth should be controlled at about 100mm. Observe the bending, warping and cutting state of the intermediate billet after cutting. If there is serious bending, serious warping, incomplete cutting or delamination after cutting, return the intermediate plate immediately.

[0066] 7.9 Before production, the mill roll gap adjustment should be confirmed on site during rough rolling to ensure the straightness of the intermediate billet. Adjustments should be made in time during production and the plate shape should be confirmed to be in good condition during finishing rolling.

[0067] 7.10 Before finishing rolling production, confirm the use of cooling water between the stands to avoid excessive cooling intensity and pit defects.

[0068] 7.11 During finishing rolling, confirm the usage status of the side guide plates to avoid excessive wear and tear during online use, which may cause burrs and scratches.

[0069] Confirm that the transition plate, side guide plate, etc. in the frame are in the correct position, and confirm that there are no scratches on the upper and lower surfaces before and during rolling.

[0070] Use maintenance to clean the rack, and confirm that there are no foreign objects in the channel before production, ensure that the channel is clean and tidy, and prevent foreign objects from being pressed in.

[0071] 7.12 During finishing rolling, the mill frame shall adopt large bending roll force to avoid excessive convexity of the plate and strip. The plate shape shall be well controlled and no plate shape defects that can be detected by visual inspection shall be present.

[0072] 7.13 Before production, confirm that there are no dead rollers on the cold roller conveyor and control the number of idle rollers. If there are scratch defects, production shall not be allowed.

[0073] Before production, use the maintenance time to adjust and confirm the laminar side spray and layer cooling status, calibrate the laminar cooling system, ensure uniform cooling of the coils, and avoid abnormal plate shape caused by cooling.

[0074] 7.14 Before production in the winding area, confirm the status of the pinch rollers to avoid rubbing marks.

[0075] Adjust the AJC step control during coiling to prevent indentation defects caused by inaccurate stepping.

[0076] When winding, check the pinch rollers, auxiliary rollers, and support rollers, etc., and no roller marks should be produced in the winding area.

[0077] When coiling, confirm the condition of the transition plate. If there are scratches, production is not allowed.

[0078] 7.15 Carefully check the surface quality of the steel coil after rolling to ensure that there are no defects such as bubbles, cracks, inclusions, splits, bulges, delamination, etc. on the surface of the steel coil.

[0079] 7.16 Sampling: Stainless steel composite plates shall be delivered in batches. Each batch shall consist of coils of the same grade of base and cladding, same specifications, same production process, and same heat treatment system.

[0080] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are within the scope of the technical solution of the present invention.

Claims

1. A hot rolling process for stainless steel composite plate, characterized in that: include: S1. Selecting materials for the base plate and the cover plate, and compounding them to obtain a slab; The base plate is 65Mn and the cover plate is 304 stainless steel; the composite structure from bottom to top is: first base plate, first cover plate, second cover plate, second base plate; S2. Heating in the heating furnace: The slab is heated to the rolling temperature before being taken out of the furnace; the furnace time of 65Mn is not less than 300 minutes; the high temperature period time is not less than 90 minutes; the heating temperature is not less than 1230℃; the temperature difference between the rough rolling and final polishing steel and the plate temperature is ±30℃, and the average temperature between furnaces of the rough rolling and final polishing steel is within 25℃; the furnace adopts a weak oxidizing atmosphere; S3. Use high-pressure water to remove primary iron oxide; S4. Rough rolling: After heating, the qualified slab is rough rolled in 5 passes; the single-row header for rough descaling is opened, and descaling is performed in passes 1 and 5. The tapping temperature of the final rough rolling pass is 1120±20℃, and the intermediate slab thickness is 49cm; S5, cutting head, before rolling 20 pieces of steel, the cutting head length is adjusted to 100mm; S6, finishing rolling, finished product thickness less than 9.0mm, using seven stands; finished product thickness not less than 9.0mm, rolling in stands 2 and 5; in terms of roll profile configuration, the work rolls adopt a concave roll profile with a concave of 0.12mm for rolling; fine descaling uses a single row of scales, and the cooling water and reverse spray between each stand are turned off; the finishing rolling temperature is: 65Mn composite slab is controlled at 860±20℃; S7, strip laminar cooling, using cooling water for forced cooling, no cooling of the edge, and rapid cooling of the front section; cooling rate control: front section cooling rate V1 is 19.20℃ / s, rear section cooling rate V2 is 12.30℃ / s; S8. The double-sided composite plate coil after fine rolling is transported to the coiling mechanism via the transmission roller for coiling. The coiling temperature is: the 65Mn composite plate billet is controlled at 630±20℃.

2. The hot rolling process of the stainless steel composite plate according to claim 1, characterized in that: In S1 , the thickness of the first substrate is 85 mm, the thickness of the first cover plate is 16 mm, the thickness of the second cover plate is 16 mm, and the thickness of the second substrate is 85 mm.

3. The hot rolling process of the stainless steel composite plate according to claim 1, characterized in that: It also includes S9, inspection and warehousing, and the coiled plates are numbered, bundled, and put into storage.

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