Production method of 65 # steel for drawing hard wire

Abstract

The invention discloses a production method of 65 # steel for drawing a hard wire, and belongs to the technical field of steel smelting and rolling. The method comprises the following steps: steelmaking: setting the N content control range of a casting blank to be less than or equal to 60ppm; weak stirring is adopted in refining, and argon gas is 200-400 NL / min; the degree of superheat is controlled within 30 DEG C, and the segregation index of the carbon element is controlled below 1.06; the pulling speed is 2.2 + / -0.1 m / min; steel rolling: the initial rolling temperature is 1030 + / -20 DEG C, the finish rolling temperature is 930 + / -20 DEG C, and the spinning temperature is 900 + / -15 DEG C; the opening degrees of the fans are as follows: the opening degrees of the fans 1 # to 6 # are 100%, and the opening degrees of the fans 7 # to 10 # are 50%; and a Stelmor roller way speed table is set. The 65 # steel disclosed by the invention has the properties that Rm is more than or equal to 900MPa, the area reduction is more than or equal to 30 percent, and the percentage elongation after fracture is more than or equal to 12 percent; the sorbite content is not less than 80%, the central martensite island is not more than grade 2, and the decarburized layer depth is not more than 1.5 D%.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel smelting and rolling technology, and particularly relates to a production method for drawing 65# steel for hard wire. Background Technology

[0002] The hardened wire products obtained after drawing 65# steel are mainly used to manufacture steel strands, steel ropes, and cold-drawn and tempered bead wires. Since the final downstream processing step for the rolled base material is drawing, high requirements are placed on various performance indicators of the product, most importantly drawing performance and coil strength. The biggest defects in the early production products were pen-tip fracture surfaces and significant differences in tensile strength within the same coil. Analysis revealed that these two problems were caused by the influence of the steel billet quality and unreasonable controlled rolling and cooling processes. Summary of the Invention

[0003] The purpose of this invention is to provide a production method for 65# steel used in drawing hard wire. The main objectives are twofold: first, to optimize key control processes in steelmaking to produce high-quality cast billets; and second, to optimize the controlled rolling and controlled cooling processes of the Morgan 5th generation rolling mill, resulting in a sorbitic microstructure with a pearlite lamellar spacing of 0.1-0.3 μm. Higher sorbitization rates in the finished product lead to better drawing performance. This ensures that the 65# steel meets customer performance requirements, achieving Rm≥900MPa, reduction of area≥30%, elongation after fracture≥12%, sorbite content≥80%, central martensite islands≤2, and decarburization layer depth≤1.5D. Furthermore, the product is free of dimensional and appearance defects.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] This invention discloses a production method for 65# steel used in drawing hard wire, with the main production processes 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—Stelmore cooling—coil collection—trimming—sampling and inspection—collection and packaging—weighing—finished product; Specifically:

[0006] Steelmaking process:

[0007] The nitrogen content of the billet is controlled within the range of ≤60ppm; weak stirring is used in refining with argon gas at 200-400NL / min to prevent nitrogen accumulation in exposed molten steel.

[0008] The superheat is controlled within 30℃ to keep the carbon segregation index below 1.06;

[0009] The target constant pulling speed is 2.2 ± 0.1 m / min;

[0010] Steel rolling process:

[0011] The initial rolling temperature is 1030±20℃, the finishing rolling temperature is 930±20℃, and the wire drawing temperature is 900±15℃.

[0012] Fan opening degree: Fans #1-6# are 100% open, fans #7-10# are 50% open;

[0013] The Steyrmo roller conveyor speed settings are as follows:

[0014]

[0015] Furthermore, the chemical composition of the 65# steel by mass percentage is as follows: C: 0.63-0.67%; Si: 0.20-0.30%; Mn: 0.50-0.60%; P≤0.025%; S: ≤0.020%; residual elements Cr≤0.03%, Ni≤0.02%, Cu≤0.02%, with the remainder being Fe and unavoidable impurities.

[0016] Furthermore, the constant pulling speed is 2.2 m / min.

[0017] Furthermore, the constant pulling speed is 2.1 m / min.

[0018] Furthermore, the Z8 and export speed can be finely adjusted by ±0.2 m / s according to the actual situation.

[0019] Furthermore, the finished product has a sorbitic structure with a pearlite lamellar spacing of 0.1-0.3 μm. The higher the sorbitization rate of the finished product, the better the drawing performance.

[0020] Furthermore, the 65# steel meets the following requirements: Rm≥900MPa, reduction of area≥30%, elongation after fracture≥12%; sorbite content≥80%, central martensite island ≤2 grade, decarburization layer depth≤1.5D%; and the product dimensions and appearance are free from defects.

[0021] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0022] The production method of this invention produces a sorbitic microstructure with a pearlite lamellar spacing of 0.1-0.3 μm. Higher sorbitization results in better drawability. This ensures that 65# steel meets customer performance requirements, achieving Rm≥900MPa, reduction of area≥30%, and elongation after fracture≥12%. The sorbite content is ≥80%, central martensite islands ≤2, and decarburization layer depth ≤1.5D. Furthermore, the product has no dimensional or appearance defects. Detailed Implementation

[0023] A method for producing 65# steel for drawing hard wire includes:

[0024] 1) Strict control of nitrogen content in the cast billet is required. The test results are shown in the table below:

[0025]

[0026] The specific chemical compositions of each implementation case are shown in the table below:

[0027]

[0028]

[0029] Through the implementation of steelmaking technology scheme 1), the nitrogen content of the gas was detected to have decreased significantly and stabilized within a fixed range, which played a crucial role in reducing work hardening during deep processing of continuously cast billets.

[0030] 2) Two 65# steel billets were selected, and the inspection results of 5 points on each billet are shown in the table below:

[0031] Table 3. Results of carbon segregation test at low superheat (26℃)

[0032]

[0033] Through the implementation of steelmaking technology scheme 2), the carbon segregation index of the billet was controlled within 1.06, reducing defects such as shrinkage cavities in the center of the billet and abnormal structures caused by uneven composition during the cooling process.

[0034] 3) The results of constant pulling speed control are shown in the table below:

[0035]

[0036] Through the implementation of steelmaking technology scheme 3), the improved continuous casting billet casting speed was stabilized and controlled, the phenomenon of hollow continuous casting billets was basically eliminated, and the phenomenon of excessive oxygen content in the gas during continuous casting was prevented.

[0037] In each embodiment, the initial rolling temperature is 1030°C, the finishing rolling temperature is 930°C, and the wire drawing temperature is 900°C.

[0038] The improvement in the stability of the product's mechanical properties is shown in the table below:

[0039]

[0040] Through the implementation of the steel rolling technology solution, the sorbite content and mechanical properties of the product fully meet the design requirements.

[0041] 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 method for producing 65# steel for drawing hard wire, characterized in that, include: Steelmaking process: The nitrogen content of the billet is controlled within the range of ≤60ppm; weak stirring is used in refining with argon gas at 200-400NL / min to prevent nitrogen accumulation in exposed molten steel. The superheat is controlled within 30℃ to keep the carbon segregation index below 1.06; The target constant pulling speed is 2.2 ± 0.1 m / min; Steel rolling process: The initial rolling temperature is 1030±20℃, the finishing rolling temperature is 930±20℃, and the wire drawing temperature is 900±15℃. Fan opening degree: Fans #1-6# are 100% open, fans #7-10# are 50% open; The Steyrmo roller conveyor speed settings are as follows:

2. The method for producing 65# steel for drawing hard wire according to claim 1, characterized in that, The chemical composition of the 65# steel by weight percentage is as follows: C: 0.63-0.67%; Si: 0.20-0.30%; Mn: 0.50-0.60%; P≤0.025%. S: ≤0.020%; residual elements Cr≤0.03%, Ni≤0.02%, Cu≤0.02%, the remainder being Fe and unavoidable impurities.

3. The method for producing 65# steel for drawing hard wire according to claim 1, characterized in that, Constant pulling speed 2.2m / min.

4. The method for producing 65# steel for drawing hard wire according to claim 1, characterized in that, Constant pulling speed 2.1m / min.

5. The method for producing 65# steel for drawing hard wire according to claim 1, characterized in that, Z8 and the export speed can be finely adjusted by ±0.2 m / s according to the actual situation.

6. The method for producing 65# steel for drawing hard wire according to claim 1, characterized in that, The finished product has a sorbitic structure with a pearlite lamellar spacing of 0.1-0.3 μm. The higher the sorbitization rate of the finished product, the better the drawing performance.

7. The method for producing 65# steel for drawing hard wire according to claim 1 or 6, characterized in that, The 65# steel meets the following requirements: Rm≥900MPa, reduction of area≥30%, elongation after fracture≥12%; sorbite content≥80%, central martensite island≤2 grade, decarburization layer depth≤1.5D%; and the product dimensions and appearance are free from defects.

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