Process method for regulating and controlling yield strength of carbon structural steel BTWJ-XN
By coordinating the adjustment of hot rolling coiling temperature and continuous annealing furnace temperature, and optimizing the coiling and annealing processes, the problem of insufficient precision in controlling the yield strength of BTWJ-XN was solved, achieving stable matching of product performance and cost optimization.
Patent Information
- Application Number
- CN202511777487.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-28
- Publication Date
- 2026-01-16
AI Technical Summary
Existing technologies make it difficult to precisely control the yield strength of carbon structural steel BTWJ-XN, resulting in some products exceeding customer requirements. Furthermore, adjusting the process is costly and lacks precision.
By coordinating the adjustment of hot rolling coiling temperature and the heating and homogenization temperature in the continuous annealing furnace zone, optimizing the coiling machine temperature control and continuous annealing furnace process parameters, the stability and uniformity of coiling temperature are ensured, and the yield strength is precisely reduced.
The yield strength of BTWJ-XN products has been precisely controlled within the range of 260-270MPa, meeting customer requirements while maintaining the stability and consistency of other mechanical properties, thus reducing production costs and equipment modification costs.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of heat treatment technology for steel materials, and particularly relates to a process method for controlling the yield strength of carbon structural steel BTWJ-XN. Background Technology
[0002] BTWJ-XN carbon structural steel is a commonly used steel for hardware components, possessing excellent mechanical and machinability properties, and is widely used in construction, home appliances, and machinery manufacturing. Guangzhou Xiangnan, a major customer of BTWJ-XN products, requested in July 2025 to reduce the yield strength of the product to 260-270 MPa to improve the ease of forming and processing hardware components.
[0003] Currently, the standard production process for BTWJ-XN products is a "hot rolling-continuous annealing" process, where the hot rolling coiling temperature is controlled at 650℃ and the heating and homogenization temperature in the continuous annealing furnace is controlled at 740℃. Products produced using this process have a yield strength range of 255-301MPa, with an average of 282MPa. The yield strength of some batches exceeds the upper limit of the customer's ideal range, making it difficult to meet specific customer processing requirements.
[0004] In existing technologies, methods for controlling the yield strength of steel mainly include composition adjustment, rolling process optimization, and heat treatment temperature control. Composition adjustment requires changing the addition of steelmaking alloys, which can easily increase production costs and has a long cycle. Adjusting the rolling process or a single heat treatment parameter alone often results in insufficient control precision and large performance fluctuations. For example, simply increasing the continuous annealing furnace temperature can reduce the yield strength to a certain extent, but it is difficult to accurately reach the customer's ideal range; adjusting the hot rolling coiling temperature also has limited control effect. Therefore, developing a method to accurately control the yield strength of BTWJ-XN without changing the composition and through the coordinated control of process parameters has significant practical application value. Summary of the Invention
[0005] In order to overcome the problems of insufficient precision in controlling the yield strength of BTWJ-XN products in the existing technology and difficulty in meeting specific customer needs, the purpose of this invention is to provide a process method for controlling the yield strength of carbon structural steel BTWJ-XN. By coordinating the adjustment of the hot rolling coiling temperature and the heating and homogenization temperature in the continuous annealing furnace, the yield strength can be accurately reduced, while ensuring that other mechanical properties of the product meet the standards stably.
[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:
[0007] This invention discloses a process for controlling the yield strength of carbon structural steel BTWJ-XN, comprising:
[0008] 1) Hot rolling process: After heating, rough rolling, and finish rolling, the BTWJ-XN steel billet is coiled. The coiling temperature is increased from the original 650℃ to 665℃. By optimizing the coiling machine temperature control system, the coiling temperature fluctuation range is controlled to be 664-712℃. During the production process, the proportion of steel coils with a coiling temperature hit rate of over 97% is not less than 68%, and the proportion of steel coils with a hit rate of 90%-96% is not less than 18%, so as to ensure the stability of the coiling temperature.
[0009] 2) Continuous annealing process: The hot-rolled steel coil is fed into a continuous annealing furnace and passes through a heating section, a soaking section, a cooling section, and a leveling section in sequence; the temperature of the heating section and the soaking section is increased from the original 740℃ to 755℃, and the holding time is controlled within 3-5 minutes to homogenize the internal structure of the steel coil; then it is cooled to room temperature at a cooling rate of 2.2-2.5℃ / min, and finally leveled by a leveling machine to obtain the finished steel coil;
[0010] The chemical composition of the carbon structural steel BTWJ-XN by mass percentage includes: C 0.06~0.08%, Si≤0.080%, Mn 0.15~0.25%, P≤0.020%, S≤0.012%, Alt 0.020~0.045%, N≤0.0050%, Ca 0.0008~0.0020%, with the remainder being Fe and impurities.
[0011] Furthermore, the chemical composition of the carbon structural steel BTWJ-XN by mass percentage includes: C 0.07%, Si 0.010%, Mn 0.20%, P 0.010%, S 0.005%, Alt 0.030%, N 0.0030%, Ca 0.0014%, with the remainder being Fe and impurities.
[0012] Further, the hot rolling process: The BTWJ-XN steel billet is heated to 1200℃, and after rough rolling and finish rolling, it is coiled. The coiling temperature is set to 665℃ and adjusted in real time through the coiling machine temperature feedback system. The actual coiling temperature is 664℃, with a hit rate of 100%.
[0013] Further, the continuous annealing process: the hot-rolled steel coil is fed into a continuous annealing furnace, the heating temperature is set to 755℃, held for 3 minutes, cooled to 40℃ at a rate of 2.3℃ / s, and then leveled by a leveling machine to obtain the finished product.
[0014] Further, the hot rolling process: the BTWJ-XN steel billet is heated to 1190℃, and after rough rolling and finish rolling, it is coiled. The coiling temperature is set at 665℃, the actual coiling temperature is 712℃, and the hit rate is 97.2%.
[0015] Further, the continuous annealing process: the hot-rolled steel coil is fed into a continuous annealing furnace, the heating temperature is set to 755℃, held for 3 minutes, cooled to 40℃ at a rate of 2.2℃ / s, and then leveled by a leveling machine to obtain the finished product.
[0016] Further, the hot rolling process: the BTWJ-XN steel billet is heated to 1210℃, and after rough rolling and finish rolling, it is coiled. The coiling temperature is set at 665℃, the actual coiling temperature is 680℃, and the hit rate is 95.4%.
[0017] Further, the continuous annealing process: the hot-rolled steel coil is fed into a continuous annealing furnace, the heating temperature is set to 755℃, held for 3 minutes, cooled to 40℃ at a rate of 2.5℃ / sn, and then leveled by a leveling machine to obtain the finished product.
[0018] Compared with the prior art, the beneficial technical effects of the present invention are as follows:
[0019] 1. This invention, by coordinating the adjustment of hot rolling coiling temperature and continuous annealing furnace temperature, can precisely control the yield strength of BTWJ-XN products at 260-270MPa without changing the steel composition or modifying existing equipment, perfectly matching customer needs and improving product applicability.
[0020] 2. The process adjustment range is small and the operation is simple. During the control process, the product's tensile strength, elongation after fracture and other performance indicators are stable and meet the standards, with no performance risks.
[0021] 3. Hot rolling coiling has high temperature control precision and good process repeatability, making it suitable for large-scale industrial production and significantly enhancing the market competitiveness of enterprises. Detailed Implementation
[0022] The present invention will be further described in detail below with reference to specific embodiments.
[0023] The specific components (wt%) of each embodiment are as follows:
[0024]
[0025] The remainder consists of iron and impurities.
[0026] Example 1
[0027] A process for controlling the yield strength of carbon structural steel BTWJ-XN, comprising the following steps:
[0028] 1. Hot rolling process: The BTWJ-XN steel billet is heated to 1200℃, and after rough rolling and finish rolling, it is coiled. The coiling temperature is set to 665℃ and adjusted in real time through the coiling machine temperature feedback system. The actual coiling temperature is 664℃, with a hit rate of 100%.
[0029] 2. Continuous annealing process: The hot-rolled steel coil is fed into a continuous annealing furnace, heated to a homogenization temperature of 755℃, held for 3 minutes, and then cooled to 40℃ at a rate of 2.3℃ / s. After being leveled by a leveling machine, the finished product is obtained. Testing shows that the finished product has a yield strength of 263MPa, a tensile strength of 366MPa, and an elongation after fracture of 37.0%, meeting customer and standard requirements.
[0030] Example 2
[0031] A process for controlling the yield strength of carbon structural steel BTWJ-XN, comprising the following steps:
[0032] 1. Hot rolling process: The BTWJ-XN steel billet is heated to 1190℃, and after rough rolling and finish rolling, it is coiled. The coiling temperature is set at 665℃, the actual coiling temperature is 712℃, and the hit rate is 97.2%.
[0033] 2. Continuous annealing process: The hot-rolled steel coil is fed into a continuous annealing furnace, heated to a homogenization temperature of 755℃, held for 3 minutes, and then cooled to 40℃ at a rate of 2.2℃ / s. After being leveled by a leveling machine, the finished product is obtained. Testing shows that the finished product has a yield strength of 264MPa, a tensile strength of 384MPa, and an elongation after fracture of 37.5%, meeting customer and standard requirements.
[0034] Example 3
[0035] A process for controlling the yield strength of carbon structural steel BTWJ-XN, comprising the following steps:
[0036] 1. Hot rolling process: The BTWJ-XN steel billet is heated to 1210℃, and after rough rolling and finish rolling, it is coiled. The coiling temperature is set at 665℃, the actual coiling temperature is 680℃, and the hit rate is 95.4%.
[0037] 2. Continuous annealing process: The hot-rolled steel coil is fed into a continuous annealing furnace, heated to a homogenization temperature of 755℃, held for 3 minutes, and then cooled to 40℃ at a rate of 2.5℃ / sn. After being leveled by a leveling machine, the finished product is obtained. Testing shows that the finished product has a yield strength of 262MPa, a tensile strength of 375MPa, and an elongation after fracture of 36.8%, meeting customer and standard requirements.
[0038] Experimental verification and effect analysis
[0039] To verify the effectiveness of the process method of this invention, multiple sets of comparative experiments were conducted, as follows:
[0040] 1. Experimental Design:
[0041] Control group 1: Produced using the original process (hot rolling coiling at 650℃ + continuous annealing furnace temperature at 740℃), as the benchmark.
[0042] Control group 2: Only the continuous annealing furnace temperature was increased to 755℃ (hot rolling coiling 650℃).
[0043] Control group 3: Only the hot rolling coiling temperature was increased to 665℃ (continuous annealing furnace temperature 740℃).
[0044] Experimental group: The process of this invention was adopted (hot rolling coiling at 665℃ + continuous annealing furnace temperature at 755℃).
[0045] 2. Comparison of mechanical properties:
[0046] The mechanical properties of the products from each scheme are compared in the table below. All products meet the standard requirements of "yield strength ≥ 195 MPa, tensile strength 315-430 MPa, and elongation after fracture ≥ 24%".
[0047]
[0048] The data shows that the yield strength of the experimental group products dropped to 263MPa, which falls precisely within the customer's ideal range of 260-270MPa. Compared with the control group 1, it was reduced by 19MPa, and the control effect was significant. At the same time, the tensile strength and elongation after fracture were basically the same as other groups, with no significant fluctuations, ensuring the comprehensive performance of the products.
[0049] 3. Process stability verification:
[0050] The test group produced a total of 22 coils of products, with a total weight of 501 tons. 15 coils had a hot rolling temperature hit rate of over 97%, accounting for 68.2%; 4 coils had a hit rate of 90%-96%, accounting for 18.2%; and 3 coils had a hit rate of 78%-89%, accounting for 13.6%. Overall, the temperature control was stable and the process repeatability was good.
[0051] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.
Claims
1. A process for regulating the yield strength of carbon structural steel BTWJ-XN, characterized in that: Comprise: 1). Hot rolling process: the BTWJ-XN billet is heated, roughed, and finished, and then coiled, the coiling temperature is increased from the original 650 DEG C to 665 DEG C, the coiling temperature fluctuation range is controlled to be 664-712 DEG C by optimizing the coiler temperature control system; during production, the proportion of the steel coils with coiling temperature hit rate exceeding 97% is ensured to be not less than 68%, the proportion of the steel coils with coiling temperature hit rate being 90%-96% is ensured to be not less than 18%, so as to ensure the stability of the coiling temperature; 2). Continuous annealing process: the hot-rolled steel coil is sent into a continuous annealing furnace, and sequentially passes through a heating section, a soaking section, a cooling section and a flattening section; the temperature of the heating section and the soaking section is increased from the original 740 DEG C to 755 DEG C, the soaking time is controlled to be within 3-5 min, so that the internal organization of the steel coil is homogenized; then the steel coil is cooled to room temperature at a cooling speed of 2.2-2.5 DEG C / min, and finally is flattened by a flattening machine to obtain a finished steel coil; The carbon structural steel BTWJ-XN has the following chemical components in percentage by mass: C 0.06-0.08%, Si <=0.080%, Mn 0.15-0.25%, P <=0.020%, S <=0.012%, Alt 0.020-0.045%, N <=0.0050%, Ca 0.0008-0.0020%, and the rest is Fe and impurities.
2. The process for regulating the yield strength of carbon structural steel BTWJ-XN according to claim 1, characterized in that: The carbon structural steel BTWJ-XN has the following chemical components in percentage by mass: C 0.07%, Si 0.010%, Mn 0.20%, P 0.010%, S 0.005%, Alt 0.030%, N 0.0030%, Ca 0.0014%, and the rest is Fe and impurities.
3. The process for regulating the yield strength of carbon structural steel BTWJ-XN according to claim 1, characterized in that: Hot rolling process: the BTWJ-XN billet is heated to 1200 DEG C, roughed, finished, and then coiled, the coiling temperature is set to be 665 DEG C, the actual coiling temperature is 664 DEG C by real-time adjustment through the coiler temperature feedback system, and the hit rate is 100%.
4. The process for regulating the yield strength of carbon structural steel BTWJ-XN according to claim 2, characterized in that: Continuous annealing process: the hot-rolled steel coil is sent into a continuous annealing furnace, the heating and soaking temperature is set to be 755 DEG C, the soaking time is 3 min, the steel coil is cooled to 40 DEG C at a speed of 2.3 DEG C / s, and then is flattened by a flattening machine to obtain a finished product.
5. The process for regulating the yield strength of carbon structural steel BTWJ-XN according to claim 1, characterized in that: Hot rolling process: the BTWJ-XN billet is heated to 1190 DEG C, roughed, finished, and then coiled, the coiling temperature is set to be 665 DEG C, the actual coiling temperature is 712 DEG C, and the hit rate is 97.2%.
6. The process for regulating the yield strength of carbon structural steel BTWJ-XN according to claim 5, characterized in that: Continuous annealing process: the hot-rolled steel coil is sent into a continuous annealing furnace, the heating and soaking temperature is set to be 755 DEG C, the soaking time is 3 min, the steel coil is cooled to 40 DEG C at a speed of 2.2 DEG C / s, and then is flattened by a flattening machine to obtain a finished product.
7. The process for regulating yield strength of carbon structural steel BTWJ-XN according to claim 1, characterized in that: Hot rolling process: the BTWJ-XN billet is heated to 1210 DEG C, roughed, finished, and then coiled, the coiling temperature is set to be 665 DEG C, the actual coiling temperature is 680 DEG C, and the hit rate is 95.4%.
8. The process for regulating the yield strength of carbon structural steel BTWJ-XN according to claim 7, characterized in that: Continuous annealing process: the hot-rolled steel coil is sent into a continuous annealing furnace, the heating and soaking temperature is set to be 755 DEG C, the soaking time is 3 min, the steel coil is cooled to 40 DEG C at a speed of 2.5 DEG C / s, and then is flattened by a flattening machine to obtain a finished product.