Cogging and quality control process for square steel of 37MnB5 alloy cold heading steel

Abstract

The invention discloses a 37MnB5 alloy cold heading square steel cogging and quality control process, and relates to the technical field of alloy cold heading square steel production. The cogging and quality control process for the square steel of the 37MnB5 alloy cold heading steel comprises the following process steps of S1, raw material preparation, S2, heating link, S3, rolling flow, S4, finishing and coping procedure, S5, inspection and acceptance and S6, delivery conditions, the raw material acceptance is strict, and components are accurately controlled: a 240 square billet and a 350 * 430 bloom are definitely adopted as raw materials, and the steel is subjected to cogging and quality control; and the contents of chemical components such as carbon, silicon and manganese are accurately controlled, so that the basic performance stability of the steel is ensured, the product quality is improved from the source, the performance fluctuation caused by raw material problems is reduced, and the rejection rate is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of the production of alloy cold-heading steel square steel, and particularly relates to the blooming and quality control process of 37MnB5 alloy cold-heading steel square steel. Background Art

[0002] In modern industrial production, alloy cold-heading steel is widely used in the manufacture of various high-strength fasteners, such as bolts for automobile engines, connecting bolts for building steel structures, etc. Its quality directly affects the performance and safety of related products. As an important alloy cold-heading steel, 37MnB5 poses strict requirements for the blooming and quality control of its square steel.

[0003] There are many drawbacks in the traditional production process of alloy cold-heading steel square steel. In terms of raw material selection, there is a lack of precise composition control standards, resulting in large fluctuations in the performance of the steel. In the heating process, the control of temperature and time is not precise enough, and the billets are prone to uneven heating, and the problem of yin-yang surfaces often occurs, affecting the subsequent rolling quality. During the rolling process, the means of controlling dimensional accuracy and surface quality are limited, and the wear of components such as rolling grooves and guides is not effectively monitored, making it easy for defects such as folds, scratches, and pitting to appear on the product surface. The finishing and grinding processes lack standardized procedures, and the phenomena of mixing quality and mixing numbers are difficult to eliminate. Incomplete grinding leads to a high rate of non-conforming products. In the inspection and acceptance link, the detection standards are not detailed enough, and the flaw detection technology is relatively backward, unable to accurately identify tiny defects, resulting in some products with potential quality hazards flowing into the market. These problems not only reduce product quality and production efficiency but also increase production costs, making it difficult to meet the growing market demand. Summary of the Invention

[0004] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art, and provide a blooming and quality control process for 37MnB5 alloy cold-heading steel square steel, which can solve the problems in the background art.

[0005] To achieve the above purpose, the present invention provides the following technical solutions: A blooming and quality control process for 37MnB5 alloy cold-heading steel square steel, including the following process steps:

[0006] S1 Raw Material Preparation:

[0007] Raw Material Selection: 240 square billets or 350×430 large square billets can be used as production raw materials;

[0008] Raw material acceptance: The size, weight, shape and surface quality of the raw material billet are inspected. The chemical composition of the raw material must meet specific standards, including carbon content controlled at 0.35-0.40%, silicon content ≤0.30%, manganese content 1.15-1.45%, phosphorus content ≤0.025%, sulfur content ≤0.025%, boron content 0.0008-0.0050%. At the same time, it is necessary to ensure that the residual Ni and Cu content in the steel is not more than 0.20%, and the residual Mo content is not more than 0.06%. The production is organized according to the target composition, and the steel is judged according to the internal control composition;

[0009] S2 heating stage:

[0010] Heating system: for 240×240 billet, preheating section temperature ≤850℃, time ≥40min; heating section temperature 1190±30℃, time ≥40min; soaking section temperature 1190±30℃, time ≥40min,

[0011] For 350×430 billet, the preheating section temperature is ≤850℃, the time is ≥80min; the heating section temperature is 1190±30℃, the time is ≥80min; the soaking section temperature is 1190±30℃, the time is ≥80min;

[0012] S3 rolling process:

[0013] Rolling standards: The radius of the square steel corner is 20mm, the side length tolerance is ±5mm, and the diagonal length difference is 7mm; the curvature per meter shall not be greater than 20mm, the total curvature shall not be greater than 2.0% of the total length, and the fixed length and uniform length control shall be done well;

[0014] Rolling operation requirements: Use descaling rolling to completely remove the surface iron oxide scale to prevent the surface pitting defects caused by the iron oxide scale rolling in;

[0015] The starting rolling temperature is ≥1000℃, and the final rolling temperature is ≥850℃;

[0016] S4 finishing and grinding process:

[0017] Cooling and cleaning: Square steel shall not be cooled by blower on the cooling bed. The distance between steel bars after the marshaling chain is not less than 150mm;

[0018] Stacking and grinding: When the square steel is stacked and slowly cooled, each steel bar should be squeezed tightly to prevent cold bending. The surface quality of the rolled billets should be checked one by one. The folds, scratches, ears, scars, cracks and flash defects on the surface of the finished product should be ground off. Billets with defects that cannot be ground off should be treated as unqualified products.

[0019] S5 Inspection and Acceptance:

[0020] Size and Shape Inspection: The size, shape and allowable deviations of 150-square rolled billets shall comply with relevant standards. The allowable deviation of the side length is -2 to +5 mm, the difference in length between adjacent sides is ≤ 3 mm, the difference in diagonal length is 5 mm, the fillet radius is ≥ 20 mm, the belly or depression depth is ≤ 4.0 mm, the end cutting skew is ≤ 12 mm, the camber per meter is ≤ 4 mm, the flatness (camber) is ≤ 0.4%L, and the specified length L is 12000 ± 100 mm;

[0021] Delivery Conditions of S6:

[0022] The product shall be delivered in the hot-rolled and fully ground state.

[0023] Preferably, the key points of the heating operation in the S2 heating link: strictly control the heating temperature and residence time in the furnace in accordance with the heating system to ensure uniform overall temperature of the billet and avoid visible yin-yang surfaces. If the yin-yang surfaces are obvious, stop rolling immediately and wait for the temperature to normalize before tapping steel.

[0024] Preferably, during the rolling process of the S3 rolling process, measure the shape dimensions of each stand every hour. If folds or scratches are found on the surface of online pickling for each batch, stop the machine for inspection. If cracks or folds are found, the quality shall be blocked by the dispatching director, and the sampling personnel shall record the situation of the defective online pickling surface for each batch in the MES system.

[0025] Preferably, when going onto the cooling bed in the S3 rolling process, there shall be no less than 3 teeth between each billet.

[0026] Preferably, for the finished product in the S3 rolling process, do not use a blower for air cooling on the cooling bed. Move the first heat preservation cover to the fast-lowering position, open the side plates of the remaining heat preservation covers and pull them apart about 1.5 meters. Inspect the surface of one billet per batch, and return it to the team in time after inspection.

[0027] Preferably, the inspection method for the S5 inspection and acceptance;

[0028] Side Length Measurement: Measure along the vertical direction of the length of the rolled billet with a measuring tool. Take the maximum dimension as the side length dimension, and the measuring position is outside the shear deformation zone;

[0029] Length Measurement: Measure the distance between the two shear cuts at both ends of the primary rolled billet along the center line of the side of the rolled billet as the actual length;

[0030] Grinding and Flaw Detection: The rolled billet must be fully ground. Each surface shall be ground at least 12 passes. Turn the billet over to check the surface and corners. There shall be no unground traces, visible cracks and obvious grinding burrs. Otherwise, perform manual grinding treatment. If it cannot be processed cleanly, it shall be rejected. Conduct flaw detection on the billet. If cracks, rotten steel or folding defects are found, mark them with chalk, pick them out for re-grinding and flaw detection. If the defects still cannot be eliminated, it shall be rejected.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] 1. For the bloom casting and quality control process of 37MnB5 alloy cold heading steel square billets, the raw material acceptance is strict and the composition is accurately controlled: It is clearly specified to use 240-square billets and 350×430 large square billets as raw materials, and the chemical composition is accurately controlled. The content of elements such as carbon, silicon, and manganese is precisely controlled, ensuring the stability of the basic properties of the steel, improving the product quality from the source, reducing performance fluctuations caused by raw material problems, and reducing the rejection rate.

[0033] 2. For the bloom casting and quality control process of 37MnB5 alloy cold heading steel square billets, the heating system is scientific and the temperature uniformity is good: A detailed heating system is formulated for billets of different specifications, and the temperature and time at each stage are strictly controlled. In case of accidents, the temperature is reduced in a timely manner to avoid overheating of the cast billets, effectively preventing the generation of yin-yang surfaces, ensuring the overall temperature uniformity of the cast billets. This makes the subsequent rolling process smoother, reduces rolling defects caused by uneven heating, improves the uniformity of the internal organizational structure of the product, and enhances the mechanical properties of the product.

[0034] 3. For the bloom casting and quality control process of 37MnB5 alloy cold heading steel square billets, the rolling control is fine and the dimensions and surface quality are excellent: During the rolling process, measures such as descaling rolling, controlling the rolling temperature, and regularly checking the rolling grooves are taken to effectively avoid defects such as oxide scale pressing in and surface scratches. Operations such as measuring the shape dimensions of the material every hour and timely handling surface defects ensure the dimensional accuracy and surface quality of the product, improving the qualified rate and market competitiveness of the product.

[0035] 4. For the bloom casting and quality control process of 37MnB5 alloy cold heading steel square billets, the finishing and grinding are standardized and the product quality is stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The present invention will be further described below in conjunction with the drawings and embodiments:

[0037] Figure 1 It is the process flow chart of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] This part will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the drawings. The function of the drawings is to supplement the description of the text part of the specification, enabling people to intuitively and vividly understand each technical feature and the overall technical solution of the present invention. However, it should not be construed as a limitation on the protection scope of the present invention.

[0039] In the description of the present invention, it should be understood that for the orientation description, such as the orientation or positional relationship indicated by up, down, front, back, left, right, etc., it is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention.

[0040] In the description of the present invention, "greater than", "less than", "exceeding", etc. are understood not to include the present number, and "above", "below", "within", etc. are understood to include the present number. If the first and second are described, it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence relationship of the indicated technical features.

[0041] In the description of the present invention, unless otherwise clearly defined, words such as "set", "installed", "connected", etc. should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meaning of the above words in the present invention in combination with the specific content of the technical solution.

[0042] Please refer to Figure 1 , the present invention provides a technical solution: the blooming and quality control process of 37MnB5 alloy cold heading steel square steel, including the following process steps:

[0043] S1 Raw material preparation:

[0044] Raw material selection: 240 square billets or 350×430 large square billets can be used as production raw materials;

[0045] Raw material acceptance: The dimensions, weights, shapes and surface qualities of the raw material square billets are accepted. The chemical compositions of the raw materials need to meet specific standards, in which the carbon content is controlled at 0.35 - 0.40%, the silicon content ≤ 0.30%, the manganese content 1.15 - 1.45%, the phosphorus content ≤ 0.025%, the sulfur content ≤ 0.025%, the boron content 0.0008 - 0.0050%. At the same time, it is necessary to ensure that the residual Ni and Cu contents in the steel are not greater than 0.20%, and the residual Mo content is not greater than 0.06%. Production is organized according to the target composition, and the steel is judged according to the internal control composition;

[0046] S2 Heating link:

[0047] Heating system. For 240×240 billets, the preheating section temperature ≤ 850°C, time ≥ 40 min; the heating section temperature 1190 ± 30°C, time ≥ 40 min; the soaking section temperature 1190 ± 30°C, time ≥ 40 min;

[0048] For a 350×430 blank, the temperature in the preheating section is ≤850°C and the time is ≥80 min; the temperature in the heating section is 1190±30°C and the time is ≥80 min; the temperature in the soaking section is 1190±30°C and the time is ≥80 min;

[0049] Key points of the heating operation in the S2 heating link: Strictly control the heating temperature and residence time in the furnace according to the heating system to ensure uniform overall temperature of the continuous casting billet and avoid visible yin-yang surfaces. If the yin-yang surfaces are obvious, stop rolling immediately and wait for the temperature to normalize before tapping;

[0050] S3 Rolling process:

[0051] Rolling standards: The fillet radius of the square steel is 20 mm, the allowable deviation of the side length is ±5 mm, and the difference in diagonal length is 7 mm; the camber per meter shall not be greater than 20 mm, and the total camber shall not be greater than 2.0% of the total length. Also, control the cut length and full length;

[0052] Rolling operation requirements: Adopt descaling rolling to thoroughly remove the surface scale and prevent defects such as surface pitting caused by the scale being rolled into the surface;

[0053] The starting rolling temperature is ≥1000°C and the finishing rolling temperature is ≥850°C;

[0054] During the rolling process of the S3 rolling process, measure the shape and size of the material at each stand every hour. If folds or scratches are found on the surface of each batch during online pickling, stop the machine for inspection. If cracks or folds are found, the quality shall be blocked by the dispatching director, and the sampling personnel shall record the surface conditions of each batch with defects in the MES system;

[0055] When transferring to the cooling bed in the S3 rolling process, there should be no less than 3 teeth between each piece of steel;

[0056] During the rolling process of the S3 rolling process, at least 2 samples should be taken for each batch during online pickling, and the sampling length should be no less than 150 mm. If surface defects such as folds, scratches, ears, scabs, and cracks are found on the sampled surface during online pickling, stop the machine for inspection and record the surface quality conditions;

[0057] For the finished products in the S3 rolling process, do not use a blower for air cooling on the cooling bed. Move the first insulation cover to the fast-lowering position, open the side plates of the remaining insulation covers and pull them apart by about 1.5 meters. Inspect the surface of each batch of lifted steel, and return it to the team in time after inspection;

[0058] S4 Finishing and grinding process:

[0059] Cooling and cleaning: Do not use a blower for air cooling on the cooling bed for square steel. After transferring to the marshalling chain, keep a distance of no less than 150 mm between each piece of steel.

[0060] S5 Inspection and acceptance:

[0061] Dimensions and Shape Inspection: The dimensions, shape and allowable deviations of 150-square rolled billets shall comply with relevant standards. The allowable deviation of the side length is -2 to +5 mm, the difference in length between adjacent sides is ≤ 3 mm, the difference in diagonal length is 5 mm, the fillet radius is ≥ 20 mm, the belly or depression depth is ≤ 4.0 mm, the end cutting skew is ≤ 12 mm, the camber per meter is ≤ 4 mm, the flatness (camber) is ≤ 0.4% L, and the specified length L is 12000 ± 100 mm;

[0062] Inspection methods for S5 inspection and acceptance;

[0063] Side length measurement: Use measuring tools to measure along the vertical direction of the length of the rolled billet. Take the maximum dimension as the side length dimension, and the measurement position is outside the shear deformation zone;

[0064] Length measurement: Measure the distance between the shear cuts at both ends of the blooming billet along the center line of the side of the rolled billet as the actual length;

[0065] Grinding and flaw detection: The rolled billets must be fully ground. Each surface is ground at least 12 passes. Turn the billet over to check the surface and corners. There shall be no unground traces, visible cracks and obvious grinding burrs to the naked eye. Otherwise, manual grinding treatment shall be carried out. If it cannot be processed cleanly, it shall be judged as scrapped. The steel billets shall be inspected for flaws. When cracks, rotten steel, folds and other defects are found, mark them with chalk, pick them out for re-grinding and flaw detection. If the defects still cannot be eliminated, it shall be judged as scrapped;

[0066] S6 Delivery Conditions:

[0067] The product is delivered in a hot-rolled and fully ground state.

[0068] Furthermore, the following effects are achieved by this process:

[0069] Strict raw material inspection and precise control of composition: It is clearly specified to use 240-square billets and 350×430 large square billets as raw materials, and accurately control the chemical composition, such as the content of elements like carbon, silicon, manganese, etc., ensuring the stability of the basic properties of the steel, improving the product quality from the source, reducing performance fluctuations caused by raw material problems, and lowering the scrap rate;

[0070] Scientific heating system and good temperature uniformity: Develop a detailed heating system for billets of different specifications, strictly control the temperature and time at each stage, and cool down in time in case of accidents to avoid overheating of the continuous casting billets, effectively prevent the generation of yin-yang surfaces, ensure the overall temperature of the continuous casting billets is uniform, which makes the subsequent rolling process smoother, reduces rolling defects caused by uneven heating, improves the uniformity of the internal organizational structure of the product, and enhances the mechanical properties of the product;

[0071] Fine rolling control, excellent size and surface quality: During the rolling process, we effectively avoid defects such as scale pressing and surface scratches through measures such as scale breaking rolling, rolling temperature control, and regular inspection of the rolling groove. We also measure the material size every hour and deal with surface defects in a timely manner, ensuring the product size accuracy and surface quality, and improving the product qualification rate and market competitiveness.

[0072] Standard finishing and grinding ensure stable product quality;

[0073] Comprehensive inspection and acceptance, strong quality traceability: formulate detailed inspection and acceptance standards, covering dimensions, surface quality, internal defects and other aspects, adopt a variety of inspection methods, such as measurement, flaw detection, etc., to accurately identify defects. At the same time, record data from each link to achieve quality traceability, so as to find the root cause of the problem in time and take improvement measures, continuously optimize the production process, and improve the production management level of the enterprise;

[0074] The embodiments of the present invention are described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the technical field without departing from the purpose of the present invention.

Claims

1. 37MnB5 alloy cold heading steel square steel blanking and quality control process, characterized by: The process steps include: S1 Raw material preparation: Raw material selection: 240 square billet and 350×430 large square billet can be used as production raw materials; Raw material acceptance: The size, weight, shape and surface quality of the raw material billet are inspected and accepted. The chemical composition of the raw material must meet specific standards, including carbon content controlled at 0.35-0.40%, silicon content ≤0.30%, manganese content 1.15-1.45%, phosphorus content ≤0.025%, sulfur content ≤0.025%, boron content 0.0008-0.0050%. At the same time, it is necessary to ensure that the residual Ni and Cu content in the steel is not more than 0.20%, and the residual Mo content is not more than 0.06%. The production is organized according to the target composition, and the steel is judged according to the internal control composition; S2 heating stage: Heating system: for 240×240 billet, preheating section temperature ≤850℃, time ≥40min; heating section temperature 1190±30℃, time ≥40min; soaking section temperature 1190±30℃, time ≥40min, For 350×430 billet, the preheating section temperature is ≤850℃, the time is ≥80min; the heating section temperature is 1190±30℃, the time is ≥80min; the soaking section temperature is 1190±30℃, the time is ≥80min; S3 rolling process: Rolling standard: The radius of the square steel corner is 20mm, the side length tolerance is ±5mm, and the diagonal length difference is 7mm; the curvature per meter shall not exceed 20mm, and the total curvature shall not exceed 2.0% of the total length; Rolling operation requirements: Use descaling rolling to completely remove the surface iron oxide scale to prevent the surface pitting defects caused by the iron oxide scale rolling in; The starting rolling temperature is ≥1000℃, and the final rolling temperature is ≥850℃; S4 finishing and grinding process: Cooling and cleaning: Square steel shall not be cooled by blower on the cooling bed, and the distance between steel bars after the marshaling chain is not less than 150mm; Stacking and grinding: When the square steel is stacked and slowly cooled, each steel bar should be squeezed tightly to prevent cold bending. The surface quality of the rolled billets should be checked one by one. The folds, scratches, ears, scars, cracks and flash defects on the surface of the finished product should be ground off. Billets with defects that cannot be ground off should be treated as unqualified products. S5 Inspection and Acceptance: Size and shape acceptance: The size, shape and allowable deviation of 150 square rolled square billet must comply with relevant standards. The allowable deviation of side length is -2 ~ +5mm, the difference in length of adjacent sides is ≤3mm, the difference in diagonal length is 5mm, the radius of fillet is ≥20mm, the depth of bulge or concave is ≤4.0mm, the end bevel is ≤12mm, the curvature per meter is ≤4mm, the straightness (curvature) is ≤0.4%L, and the fixed length L is 12000±100mm; Surface quality acceptance: There shall be no cracks, scars, folds, inclusions, tears, ears, or hairline marks with a depth greater than 0.8mm on the surface. Individual scratches, indentations, pits, and pits with a depth not exceeding the negative deviation are allowed on the surface; Surface defects should be removed, and the removed area should be smooth and without edges. The removal width shall not be less than 5 times the removal depth. The removal depth is calculated from the actual size. The allowable removal depth on the same section shall not exceed 10% of the nominal thickness.

2. The 37MnB5 alloy cold heading steel square steel blanking and quality control process according to claim 1 is characterized in that: The key points of the heating operation in the S2 heating link are as follows: strictly control the heating temperature and the time in the furnace according to the heating system to ensure that the overall temperature of the ingot is uniform and avoid the visible positive and negative surfaces. If the positive and negative surfaces are obvious, the rolling should be stopped immediately and the steel can be tapped after the temperature returns to normal.

3. The 37MnB5 alloy cold heading steel square steel blanking and quality control process according to claim 1 is characterized in that: During the rolling process of the S3 rolling process, the material shape size of each stand is measured every hour.

4. The 37MnB5 alloy cold heading steel square steel blanking and quality control process according to claim 1 is characterized in that: In the S3 rolling process, there shall be no less than 3 teeth on each steel partition when placing on the cooling bed.

5. The 37MnB5 alloy cold heading steel square steel blanking and quality control process according to claim 1 is characterized in that: The finished products of the S3 rolling process shall not be cooled by blowers on the cooling bed. The other side panels of the insulation cover shall be opened and pulled apart by about 1.5 meters. One steel bar shall be hoisted from each batch to inspect the surface and returned to the team in time after the inspection.

6. The 37MnB5 alloy cold heading steel square steel blanking and quality control process according to claim 1 is characterized in that: Inspection methods for the S5 inspection and acceptance; Side length measurement: Use a measuring tool to measure along the vertical direction of the length of the rolled billet, with the maximum size as the side length, and the measuring position is outside the shear deformation zone; Length measurement: The actual length is measured by measuring the distance between the notches at both ends of the billet along the center line of the side of the rolled billet; Grinding and flaw detection: The rolled billet must be fully ground, with each surface ground for at least 12 times. The surface and corners must be turned over to check. There must be no traces of ungrinding, visible cracks and obvious grinding burrs. Otherwise, manual grinding will be carried out. If the treatment is not clean, it will be scrapped. The billet will be inspected for flaws. If cracks, rotten steel, or folding defects are found, they will be marked with chalk, picked out for further grinding and flaw detection. If the defects cannot be eliminated, it will be scrapped.

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