Production method of 70 # steel wire rod for manufacturing steel wire rope
By optimizing the steelmaking and rolling processes, the problems of center segregation and inclusion control of 70# steel wire rod were solved, enabling the production of high-performance steel wire ropes using 70# steel wire rod that meets mechanical performance requirements.
Patent Information
- Application Number
- CN202511129432.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-13
- Publication Date
- 2025-11-25
AI Technical Summary
Existing technologies are insufficient to effectively control the center segregation and inclusions of 70# steel wire rod, leading to the formation of abnormal structures such as martensite and network cementite, which affects its mechanical properties.
By optimizing steelmaking and rolling processes, including controlling superheat, adjusting casting speed and secondary cooling water ratio, optimizing alloy addition sequence and argon flow rate, and combining precise rolling temperature and cooling control, gas stirring, refining slag formation, and electromagnetic stirring are employed to control billet quality and inclusion size.
The project achieved a reduction in the center segregation index of the billet to below 1.08, an inclusion level of below 2, a sorbitization rate of over 85% for the finished 70# steel, and mechanical properties of Rm≥1000MPa, reduction of area≥30%, and elongation after fracture≥12%.
Smart Images
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of wire rod casting and rolling technology, and particularly relates to a production method for 70# steel wire rod for making steel wire rope. Background Technology
[0002] 70# carbon structural steel possesses good strength, toughness, and high tensile strength. Downstream manufacturers use the hardened wire obtained after drawing to produce steel wire rope products. Downstream customers experience a maximum reduction in area of over 90% during drawing, thus imposing relatively strict requirements on the microstructure and properties of 70# steel. The microstructure must not exhibit abnormal structures such as martensite or network cementite; the sorbite content must reach over 85%; inclusions must be controlled; and the tensile strength of the base metal must reach over 1000 MPa. Analysis revealed that center segregation in the cast billet is the main cause of martensite and network cementite formation. Due to the use of silicon-aluminum-iron deoxidation, the resulting inclusions are mainly silicate inclusions. When the silicate inclusions contain a high SiO2 content, they disrupt the continuity of the steel matrix and lead to stress concentration, thereby reducing the steel's plasticity, toughness, and fatigue resistance. This type of inclusion should be removed to the greatest extent possible. The removal methods should be controlled by a combination of gas stirring, ladle argon blowing, refining slag formation, weak blowing, tundish metallurgy, and electromagnetic stirring. The sorbitization rate is mainly achieved through the design of the rolling cooling process. Cooling is controlled in two ways: first, by controlling the wire drawing temperature after water cooling; and second, by controlling the cooling rate of the wire on the air-cooled roller table, in order to obtain a higher sorbitization rate and less proeutectoid ferrite structure. Summary of the Invention
[0003] The purpose of this invention is to provide a production method for 70# steel wire rods used to manufacture steel wire ropes, with the mechanical properties meeting the following requirements: Rm≥1000MPa, reduction of area≥30%, and elongation after fracture≥12%.
[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:
[0005] This invention discloses a production method for 70# steel wire rod used in the manufacture of steel wire ropes. The main production processes are as follows: Steelmaking process: blast furnace hot metal—hot metal pretreatment—converter top and bottom blowing smelting—LF refining—small billet continuous casting—slow cooling stacking; Rolling process: billet heating—high-pressure water descaling—rough rolling—intermediate rolling—finish rolling—controlled cooling water tank—wire drawing—Stelmo cooling—coiling—trimming—sampling and inspection—collection and packaging—weighing—finished product; characterized in that:
[0006] Steelmaking process:
[0007] 1) Casting with the superheat controlled below 30℃ can effectively hinder the growth of columnar crystals, thereby reducing the occurrence of central segregation and controlling the segregation index of carbon elements below 1.08.
[0008] 2) Increase the casting speed from 2.2±0.1m / min to 2.5±0.2m / min, and at the same time reduce the secondary cooling water volume from 0.80L / kg to 0.55-0.65L / kg, so as to move the solidification end forward, enhance the fluidity of the molten steel and improve the center segregation;
[0009] 3) The optimal order of alloy addition is low-nitrogen carbon raiser + ferrosilicon + ferromanganese; secondly, adjust the argon flow rate from 200L / min to 165-175L / min (preferably 170L / min), and control the diameter of the blown area to 300-400mm; finally, maintain the soft blowing time for more than 15min, and the molten steel must not be exposed during the soft blowing process.
[0010] Steel rolling process:
[0011] 1) Rolling temperature control: initial rolling temperature 1030-1050℃, finishing rolling temperature 950±20℃, wire drawing temperature 890±120℃;
[0012] 2) Fan opening degree: Fans #1-7 are 100% open, and fans #8-10 are 50% open;
[0013] 3) The Steyrmo roller conveyor speed settings are as follows:
[0014]
[0015] Furthermore, the secondary cooling water ratio was reduced from 0.80 L / kg to 0.60 L / kg.
[0016] Furthermore, the Z8 and export speeds are fine-tuned by ±0.2 m / s based on actual conditions.
[0017] Furthermore, the chemical composition of the 70# steel by mass percentage is as follows: C: 0.67-0.75%; Si: 0.17-0.37%; Mn: 0.30-0.60%; P≤0.025%; S: ≤0.0325%; residual elements Cr≤0.10%, Ni≤0.15%, Cu≤0.20%, with the remainder being Fe and impurities.
[0018] Furthermore, the chemical composition of the 70# steel by mass percentage is as follows: C: 0.71%; Si: 0.246%; Mn: 0.553%; P: 0.01%; S: 0.007%, with the remainder being Fe and impurities.
[0019] Furthermore, the chemical composition of the 70# steel by weight percentage is as follows: C: 0.706%; Si: 0.221%; Mn: 0.538%; P: 0.013%; S: 0.004%, with the remainder being Fe and impurities.
[0020] Furthermore, the chemical composition of the 70# steel by weight percentage is as follows: C: 0.7%; Si: 0.233%; Mn: 0.539%; P: 0.014%; S: 0.008%, with the remainder being Fe and impurities.
[0021] Furthermore, the chemical composition of the 70# steel by mass percentage is as follows: C: 0.707%; Si: 0.226%; Mn: 0.593%; P: 0.02%; S: 0.008%, with the remainder being Fe and impurities.
[0022] Compared with the prior art, the beneficial technical effects of the present invention are as follows:
[0023] Optimizing the quality of the billet reduces the center segregation coefficient to below 1.08, thereby eliminating the generation of abnormal structures such as martensite and network cementite;
[0024] Through gas stirring, ladle argon blowing, refining slag formation, weak blowing, tundish metallurgy, electromagnetic stirring and other steelmaking process control methods, the size of silicate inclusions is controlled to below level 2.
[0025] The sorbitization rate of 70# steel finished products reaches over 85%;
[0026] The mechanical properties reach Rm≥1000MPa, reduction of area≥30%, and elongation after fracture≥12%. Detailed Implementation
[0027] The chemical composition and test results of the products in each embodiment are shown in the table below:
[0028]
[0029] Two 70# steel billets were selected, and the inspection results of 5 points on each billet are shown in the table below:
[0030] Carbon segregation test results at superheat (28℃)
[0031]
[0032] The results of constant speed control are shown in the table below:
[0033]
[0034] Through the implementation of steelmaking technology schemes 1 and 2, the carbon segregation index of the billet was controlled within 1.08, which provided a guarantee for reducing the generation of abnormal structures in the finished product.
[0035] The results after inclusion control are shown in the table below:
[0036] Non-metallic inclusions / grade
[0037]
[0038]
[0039] All inclusions are controlled within the range of less than 1.5.
[0040] The improvement in the mechanical property stability of 70# steel products is shown in the table below:
[0041]
[0042] The product's sorbite content and mechanical properties fully meet the design requirements.
[0043] 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 production method for 70# steel wire rod used in the manufacture of steel wire rope, comprising the following main production processes: steelmaking process: blast furnace molten iron—molten iron pretreatment—converter top and bottom re-blowing smelting—LF refining—small billet continuous casting—slow cooling stacking; rolling process: billet heating—high-pressure water descaling—rough rolling—intermediate rolling—finish rolling—controlled cooling water tank—wire drawing—Stelmore cooling—coiling—trimming—sampling inspection—collection and packaging—weighing—finished product; characterized in that, in: Steelmaking process: 1) Casting with the superheat controlled below 30℃ can effectively hinder the growth of columnar crystals, thereby reducing the occurrence of central segregation and controlling the segregation index of carbon elements below 1.
08. 2) Increase the casting speed from 2.2±0.1m / min to 2.5±0.2m / min, and at the same time reduce the secondary cooling water volume from 0.80L / kg to 0.55-0.65L / kg, so as to move the solidification end forward, enhance the fluidity of the molten steel and improve the center segregation; 3) The optimal order of alloy addition is low-nitrogen carbon raiser + ferrosilicon + ferromanganese; secondly, adjust the argon flow rate from 200L / min to 165-175L / min, and control the diameter of the blown area to 300-400mm; finally, maintain the soft blowing time for more than 15 minutes, and the molten steel must not be exposed during the soft blowing process. Steel rolling process: 1) Rolling temperature control: initial rolling temperature 1030-1050℃, finishing rolling temperature 950±20℃, wire drawing temperature 890±120℃; 2) Fan opening degree: Fans #1-7 are 100% open, and fans #8-10 are 50% open; 3) The Steyrmo roller conveyor speed settings are as follows: 。 2. The production method of 70# steel wire rod for making steel wire rope according to claim 1, characterized in that, The secondary cooling water ratio was reduced from 0.80 L / kg to 0.60 L / kg.
3. The production method of 70# steel wire rod for making steel wire rope according to claim 1, characterized in that, Z8 and the export speed can be finely adjusted by ±0.2 m / s based on the actual situation.
4. The production method of 70# steel wire rod for making steel wire rope according to claim 1, characterized in that, The chemical composition of the 70# steel by weight percentage is as follows: C: 0.67-0.75%; Si: 0.17-0.37%; Mn: 0.30-0.60%; P≤0.025%. S: ≤0.0325%; residual elements Cr≤0.10%, Ni≤0.15%, Cu≤0.20%, the remainder being Fe and impurities.
5. The production method of 70# steel wire rod for making steel wire rope according to claim 4, characterized in that, The chemical composition of the 70# steel by weight percentage is: C: 0.71%; Si: 0.246%; Mn: 0.553%; P：0.01％； S: 0.007%, the remainder is Fe and impurities.
6. The production method of 70# steel wire rod for making steel wire rope according to claim 4, characterized in that, The chemical composition of the 70# steel by weight percentage is: C: 0.706%; Si: 0.221%; Mn: 0.538%; P：0.013％； S: 0.004%, the remainder is Fe and impurities.
7. The production method of 70# steel wire rod for making steel wire rope according to claim 4, characterized in that, The chemical composition of the 70# steel by weight percentage is: C: 0.7%; Si: 0.233%; Mn: 0.539%; P：0.014％； S: 0.008%, the remainder is Fe and impurities.
8. The production method of 70# steel wire rod for making steel wire rope according to claim 4, characterized in that, The chemical composition of the 70# steel by mass percentage is: C: 0.707%; Si: 0.226%; Mn: 0.593%; P：0.02％； S: 0.008%, the remainder is Fe and impurities.