High-strength anti-seismic disc screw of 600mpa grade and production process thereof

Abstract

The application relates to the technical field of high-strength anti-seismic disc screw, in particular to a high-efficiency low-cost 600MPa-grade high-strength anti-seismic disc screw and a production process thereof, and the chemical composition and mass percentage of the high-strength anti-seismic disc screw are as follows: C: 0.23-0.28%, Si: 0.65-0.8%, Mn: 1.4-1.6%, S: less than or equal to 0.04%, P: less than or equal to 0.04%, V: 0.1-0.12%, Cr: 0.1-0.2%, N: 0.018-0.023%, and the balance is Fe and inevitable impurities. The design concept of optimal cost and quality is adopted, and a suitable production process is combined, so that the low-cost advantages of carbon, silicon, nitrogen and other elements are fully utilized, the content of vanadium elements is reduced, the 600MPa-grade disc screw product with high strength, high plasticity and excellent anti-seismic performance is produced, and the requirements of large key projects on the comprehensive performance and safety performance of steel bars are met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-strength anti-seismic coil, in particular to a kind of high-efficiency low-cost 600MPa grade high-strength anti-seismic coil and its production process. BACKGROUND

[0002] 600MPa grade high-strength steel can be widely used in large-span construction engineering and other fields due to its high strength, energy saving, environmental protection and excellent safety performance. Although the production and growth rate of high-strength steel in China have been increasing year by year in recent years, the overall proportion is still relatively low, so the 600MPa grade product has a wide application prospect.

[0003] Coil belongs to a typical wire product, with poor uniformity, poor stability of microstructure and properties. For 600MPa grade products, these problems are more prominent, so the development is more difficult. Currently, 600MPa grade anti-seismic coil is mainly produced by hot rolling process with the addition of high-cost vanadium, niobium and other micro-alloy elements. Not only the alloy cost is high, but also there are problems such as billet crack, narrow process window and non-obvious yield point of the product. In order to reduce the alloy cost, some researchers have developed a controlled rolling and controlled cooling production process with low vanadium and niobium micro-alloying. Although this process can significantly reduce the alloy cost, it requires high equipment and has low production efficiency and poor process universality, which is difficult to popularize on a large scale. SUMMARY

[0004] The present application overcomes the shortcomings of the prior art and provides a 600MPa grade high-strength anti-seismic coil product and a production method with simple production process, low alloy cost, excellent mechanical properties and safety performance. The low-cost advantages of carbon, silicon and nitrogen elements are fully utilized, and the content of vanadium element is reduced to meet the requirements of large key projects on the comprehensive performance and safety performance of steel bars.

[0005] In the first aspect, the present application provides a high-efficiency low-cost 600MPa grade high-strength anti-seismic coil. The chemical composition and mass percentage of the 600MPa grade high-strength anti-seismic coil are as follows: C: 0.23-0.28%, Si: 0.65-0.8%, Mn: 1.4-1.6%, S≤0.04%, P≤0.04%, V: 0.1-0.12%, Cr: 0.1-0.2%, N: 0.018-0.023%, and the balance is Fe and unavoidable impurities.

[0006] C element is the most economical and effective strengthening element in steel, but too high carbon content has adverse effects on the plasticity and welding performance of the product. In the present application, the upper limit of carbon content is the same as the upper limit of C content in HRB600 hot-rolled ribbed steel bar in national standard GB / T1499.2-2018, which is 0.28%. In the present application, the content of C element ranges from 0.23 to 0.28%.

[0007] Si in steel mainly to solid solution strengthening, can significantly improve the strength of steel material, and the price of manganese, vanadium and other alloy elements low, therefore the upper limit of Si content in the application is the same as the upper limit of Si content of HRB600 hot-rolled ribbed steel bar in national standard GB / T1499.2-2018, that is 0.8%.

[0008] Mn in steel mainly plays a solid solution strengthening effect, and can refine the transformed pearlite structure and improve the strength and plasticity. In the application, the Mn content is in the range of 1.4-1.6%.

[0009] P and S are typical impurity elements in steel. The cleanliness of steel requires effective reduction of P and S content, but excessive reduction of the content will increase the cost of steelmaking. In the application, the P and S content is in the range of P≤0.04% and S≤0.04%, which is higher than the national standard and does not excessively increase the product cost.

[0010] V is a strong carbonitride forming element, has a strong binding force with nitrogen, forms stable VN, and mainly utilizes the precipitation strengthening effect; at the same time, vanadium also has the effects of refining the structure and solid solution strengthening in the steel. In the application, the V content is in the range of 0.1-0.12%.

[0011] Cr is an important low-cost alloying element, which can improve the mechanical properties such as strength and hardness of deformed steel bars and corrosion resistance through solid solution strengthening and formation of chromium carbide. However, excessive chromium content will reduce the plasticity and toughness of the deformed steel bar. Therefore, in the application, an appropriate amount of chromium is used to replace the complex Nb element. In the application, the Cr content is in the range of 0.1-0.2%.

[0012] N element has a strong binding capacity with vanadium, and an appropriate amount of nitrogen element can effectively play the micro-alloying effect of vanadium element. However, excessive nitrogen content will have adverse effects on the aging performance and welding performance of the deformed steel bar. Therefore, in the application, the N content is in the range of 0.018-0.023%, and the V / N ratio is greater than 4.

[0013] The technical solution further limited by the scheme is:

[0014] Further, the chemical composition and mass percentage of the 600MPa grade high-strength anti-seismic deformed steel bar are as follows: C: 0.25-0.27%, Si: 0.65-0.8%, Mn: 1.4-1.6%, S≤0.04%, P≤0.04%, V: 0.1-0.12%, Cr: 0.1-0.2%, N: 0.018-0.023%, and the balance is Fe and unavoidable impurities.

[0015] Further, the carbon equivalent Ceq of the high-strength anti-seismic deformed steel bar is ≤0.58%, and Ceq=C+Mn / 6+(Cr+V+Mo) / 5+(Cu+Ni) / 15.

[0016] In a second aspect, the application further provides a production process of high-strength anti-seismic disc-shaped steel wire rod with a yield strength of 600 MPa, which is applied to the production of the high-strength anti-seismic disc-shaped steel wire rod according to any of the solutions in the first aspect, and comprises the following steps: casting blank heating, rolling, wire forming, and cooling, which can be specifically casting blank heating, rolling, wire feeding into pinch rollers, and wire forming by a wire forming machine, and then the disc-shaped steel wire rod is subjected to air cooling by a Stelmor air cooling line and slow cooling by a holding cover.

[0017] The technical solution defined in the solution is further limited as follows:

[0018] Further, the casting blank heating specifically comprises the following steps: feeding the prepared qualified blank into a heating furnace, heating at a temperature of 1000-1100 DEG C, soaking at a temperature of 1100-1150 DEG C, and heating the casting blank in the heating furnace for 100-120 min.

[0019] Further, in the rolling step, the rolling temperature is 1000-1050 DEG C, and the rolling process is non-controlled rolling.

[0020] Further, in the wire forming step, the wire forming temperature is 850-920 DEG C.

[0021] Further, the cooling specifically comprises the following steps: controlling the cooling of the rolling material by adjusting the roller speed, the air volume of the fan, and the cover of the Stelmor air cooling line, so as to ensure the stable mechanical properties and the refined microstructure of the finished product, the roller speed adopts the principle of low in the front and high in the back, the first roller (1# roller) speed is 80-100 rpm / min, the rest of the rollers are controlled according to the speed increase of 100%-105% in turn, the 1-3# fans are opened at 100%, the 4-5# fans are opened at 70%, the 6# / 7# fans are opened at 90%, and the 1-5# covers are opened, and the rest of the covers are closed. Through the above cooling control operation, the phase transition temperature is reached at a relatively fast cooling speed, and then slow cooling is controlled, so as to refine the microstructure after phase transition. The production process can realize the refinement of the microstructure after phase transition and the reduction of the performance difference between the same coils through the controlled cooling after rolling, thereby improving the performance stability of the product.

[0022] The production process provided by the application fully utilizes the strengthening mechanism of different occurrence states of alloy elements in the heating, rolling, and phase transition processes to improve the product strength and plasticity and the anti-seismic performance. The high-strength disc-shaped steel wire rod produced by the above process has a yield strength of more than 615 MPa, a tensile strength of more than 780 MPa, a strength-to-yield ratio of more than 1.26, a yield-to-tensile ratio of less than 1.30, and a microstructure of refined ferrite + pearlite, which meets the requirements of the new GB / T1499.2-2018 standard on the performance and microstructure of hot-rolled ribbed steel bars.

[0023] The application has the following beneficial effects:

[0024] (1) The 600MPa grade disc screw product with high strength, high plasticity and excellent anti-seismic performance is produced by the design concept of optimal cost and quality and combined with suitable production process, so as to meet the requirements of large key projects on the comprehensive performance and safety performance of steel bars;

[0025] (2) The yield strength of the high-strength disc screw produced by the application reaches more than 615MPa, the tensile strength reaches more than 780MPa, the strength-yield ratio is greater than or equal to 1.26, the yield-yield ratio is less than or equal to 1.30, the microstructure is relatively refined ferrite + pearlite, and the requirements of the new standard GB / T1499.2-2018 on the performance and metallographic structure of hot-rolled ribbed steel bars are met;

[0026] (3) The application realizes the phase change temperature by controlling the cooling speed, and then controls the slow cooling, so as to refine the phase change structure, realizes the phase change structure refinement and reduces the performance difference between the same circles by controlling the cooling after rolling, so as to improve the product performance and stability, the mechanical properties and safety are good, and the content of niobium is not added, the content of carbon, silicon and chromium is further optimized to reduce the content of vanadium, the low alloy cost advantage of the product is realized, the non-controlled rolling is adopted in the production process, and the simple controlled cooling process is matched, so that the production process is simple and convenient for production operation. DETAILED DESCRIPTION Example 1

[0027] The chemical component ratio is calculated according to the percentage by weight: C: 0.24, Si: 0.68, Mn: 1.46%, P: 0.019%, S: 0.025%, Cr: 0.11, V: 0.105%, N: 0.0189%, Ceq: 0.54%, and the rest is Fe and inevitable impurities. The above-mentioned component billet is rolled into a disc screw with a specification of 6mm, and the billet size is 150*150 square billet. The production process parameters are as follows: billet heating temperature is 1030℃, soaking temperature is 1120℃, and rolling temperature is 1000-1020℃; the speed of 1# roller is 100rpm / min, and the speed of the rest is controlled at 105%; the fans of 1-3# are opened at 100%, the fans of 4-5# are opened at 70%, and the fans of 6# / 7# are opened at 90%; the covers of 1-5# are opened, and the covers of the rest are closed.

[0028] The performance index of the product produced in the embodiment is as follows: Rel: 625MPa; Rm: 800MPa, strength-yield ratio: 1.28, yield-yield ratio: 1.05, elongation after fracture: 21.0%, maximum total elongation (Agt): 10.8%, microstructure is pearlite + ferrite, and the requirements of the new national standard on hot-rolled threaded steel are met. Example 2

[0029] Chemical composition ratio, in percentage by weight: C: 0.27, Si: 0.78%, Mn: 1.50%, P: 0.018%, S: 0.023%, Cr: 0.13, V: 0.110%, N: 0.0205%, Ceq: 0.57%, and the rest is Fe and inevitable impurities. The above-mentioned component billet is rolled into a disc screw with a specification of ϕ12 mm, and a billet with a size of 150*150 square billet is used. The production process parameters of the steel bar with the specification are as follows: billet heating temperature 1080℃, soaking temperature 1140℃, and opening rolling temperature 1030-1045℃; 1# roller 80 rpm / min, and the rest according to the speed control of 100%; 1-3# fan 100%, 4-5# fan 70%, 6# / 7# fan 90%; 1-5# cover open, and the rest cover closed.

[0030] The performance index of the product produced in the embodiment is as follows: Rel: 650 MPa; Rm: 825 MPa, strength-yield ratio: 1.27, yield-yield ratio: 1.09, elongation after fracture: 19.5%, maximum force total elongation (Agt): 10.3%, and the microstructure is pearlite + ferrite, which meets the requirements of the new national standard for hot-rolled threaded steel.

[0031] In addition to the above-mentioned embodiments, the present application can also have other embodiments. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present application.

Claims

1. A high-efficiency, low-cost, 600MPa-grade high-strength earthquake-resistant coiled screw, characterized in that, The chemical composition and mass percentage of the 600MPa grade high-strength anti-vibration coiled screw are as follows: C: 0.27%, Si: 0.65-0.8%, Mn: 1.4-1.6%, S≤0.04%, P≤0.04%, V: 0.1-0.12%, Cr: 0.13%, N: 0.018-0.023%, with the balance being Fe and unavoidable impurities; the carbon equivalent (Ceq) of the high-strength anti-vibration coiled screw is 0.57%. The production process of high-strength, earthquake-resistant coiled rebar with high efficiency and low cost includes the following steps: billet heating, rolling, coiling and cooling; the billet heating specifically includes: sending the prepared qualified billet into the heating furnace, heating temperature 1000℃-1100℃, soaking temperature 1100-1150℃, and heating time of the billet in the heating furnace for 100-120 minutes; In the rolling step, the initial rolling temperature is 1000-1050℃, and the rolling process is not controlled. The cooling process specifically includes: the Stellmore air-cooling line on the rolled material controls the cooling by adjusting the roller speed, fan air volume, and cover. The roller speed follows the principle of low speed at the beginning and high speed at the end. The roller speed of the first roller is 80-100 rpm / min, and the remaining rollers are controlled sequentially with an increase of 100%-105%. Fans #1-3 are turned on at 100%, fans #4-5 are turned on at 70%, and fans #6 / 7 are turned on at 90%. Covers #1-5 are turned on, and the remaining covers are turned off.

2. The high-efficiency, low-cost 600MPa-grade high-strength seismic-resistant coiled screw according to claim 1, characterized in that, In the spinning and coiling step, the spinning temperature is 850-920℃.