Production method of 45 # steel

Abstract

The invention discloses a production method of 45 # steel. The production method comprises the steps of blast furnace molten iron, molten iron pretreatment, converter top and bottom combined blowing smelting, LF refining, small square billet continuous casting, slow cooling and long material factory rolling. The method comprises the steps of billet heating, high-pressure water descaling, rough rolling, intermediate rolling, finish rolling, cooling water tank control, spinning, stelmor cooling, coil collecting, trimming, sampling inspection, collecting and bundling, weighing and finished wire rod obtaining. According to the production method of the 45 # steel, the 45 # steel meets the performance requirements of customers, the tensile strength can be stabilized to be 700 MPa or above, the percentage elongation after fracture is larger than or equal to 20%, the area reduction rate is larger than or equal to 45%, and the product size and appearance are free of defects.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy and rolling, and in particular relates to a production method of 45# steel. Background Art

[0002] After drawing, 45# steel is widely used in the processing of rods, shafts, bolts and other parts in the automotive, machinery and other industries. The processing technology is complex and diverse, generally including turning, hot forging, cold heading, heat treatment and other processes, and the surface quality and mechanical properties of round steel are required to be high. The national standard requires that when testing the mechanical properties of 45# steel, the sample must be normalized at 850℃ before a tensile test. Downstream processing companies generally perform a series of deformation processes before heat treating the workpiece to meet the use requirements. Therefore, the stability of the mechanical properties of 45# steel in the hot-rolled state is the main influencing factor to ensure the smoothness of its subsequent processing and production. Summary of the invention

[0003] The purpose of the present invention is to provide a production method of 45# steel, so that the 45# steel meets the performance requirements of customers, the tensile strength can be stabilized at above 700MPa, the elongation after fracture is greater than or equal to 20%, the area reduction rate is greater than or equal to 45%, and the product size and appearance have no defects.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] The present invention discloses a production method of 45# steel, comprising blast furnace molten iron - molten iron pretreatment - converter top and bottom blowing smelting - LF refining - small square billet continuous casting - slow cooling - long product mill rolling; billet heating - high-pressure water descaling - rough rolling - intermediate rolling - finishing rolling - controlled cooling water tank - wire laying - Stelmor cooling - coiling - trimming - sampling inspection - collection and bundling - weighing - finished wire rod; the main production process comprises:

[0006] 1) Gas content requirements for ingot casting: O≤30ppm, N≤60ppm; single slag or double slag operation is adopted according to the molten iron conditions, and the end point basicity is 2.7-3.5;

[0007] 2) The converter adopts high-drawing supplementary blowing operation, and the final composition of steel tapping is C ≥ 0.10%, T ≥ 1610℃;

[0008] 3) When tapping steel, strengthen the contact with the tank repairer and perform argon blowing operation according to regulations. Argon control requirements: large argon stirring in the early stage of tapping steel, and when the tapping amount is greater than 2 / 3, reduce the argon flow rate to perform slag blocking operation to ensure that the alloy does not clump and the top slag material is well melted;

[0009] 4) Starting pulling speed 0.25m / min, target constant pulling speed 2.0m / min;

[0010] 5) Rolling temperature control: starting rolling temperature 1000±20℃, finishing rolling temperature 920±20℃, spinning temperature 880±20℃;

[0011] 6) Fan opening degree: 1#-5# fans opening degree 100%, 6#-8# fans opening degree 50%;

[0012] 7) The Steyrmo roller speed setting is as follows:

[0013]

[0014] The chemical composition of the 45# steel is as follows by mass percentage: C: 0.42-0.050%; Si: 0.17-0.37%; Mn: 0.50-0.80%; P≤0.035%; S: ≤0.035%; the remainder is Fe and a small amount of impurity elements.

[0015] Furthermore, when Si≤0.5, single slag operation is performed for molten iron entering the furnace, and when Si>0.5, double slag operation is performed.

[0016] Furthermore, the gas content requirement of the ingot is: O≤28ppm.

[0017] Furthermore, the gas content requirement of the ingot is: N≤50ppm.

[0018] Furthermore, the pulling speed fluctuation range is ±0.1m / min.

[0019] Compared with the prior art, the beneficial technical effects of the present invention are:

[0020] The preparation process of the present invention can make 45# steel meet the performance requirements of customers, stabilize the tensile strength at above 700MPa, the elongation after fracture is greater than or equal to 20%, the area reduction is greater than or equal to 45%, and the product size and appearance have no defects. DETAILED DESCRIPTION

[0021] The chemical composition (mass percentage) of the 45# steel involved in the present invention is: C: 0.42-0.050%; Si: 0.17-0.37%; Mn: 0.50-0.80%; P≤0.035%; S:≤0.035%; the remainder is Fe and a small amount of impurity elements.

[0022] Main production process:

[0023] Hot metal from blast furnace - hot metal pretreatment - converter top and bottom blowing smelting - LF refining - billet continuous casting - slow cooling - long product mill rolling

[0024] Billet heating - high-pressure water descaling - rough rolling - intermediate rolling - finishing rolling - controlled cooling water tank - wire laying - Stelmor cooling - coiling - trimming - sampling inspection - collection and bundling - weighing - finished wire rod

[0025] Technology Improvement Program

[0026] 1) Gas content requirements for ingot casting: O≤30ppm, N≤60ppm; single slag or double slag operation is adopted according to the molten iron conditions (it is recommended to operate with single slag when Si≤0.5 for molten iron, and double slag operation when Si>0.5), and the end point basicity is 2.7-3.5;

[0027] 2) The converter adopts high-drawing supplementary blowing operation, and the final composition of steel tapping is C ≥ 0.10%, T ≥ 1610℃;

[0028] 3) When tapping steel, strengthen the contact with the tank repairer and perform argon blowing operation according to regulations. Argon control requirements: large argon stirring in the early stage of tapping steel, and when the tapping amount is greater than 2 / 3, reduce the argon flow rate to perform slag blocking operation to ensure that the alloy does not clump and the top slag material is well melted;

[0029] 4) Starting pulling speed 0.25m / min, target constant pulling speed 2.0m / min, pulling speed fluctuation range ±0.1m / min;

[0030] 5) Rolling temperature control: starting rolling temperature 1000±20℃, finishing rolling temperature 920±20℃, spinning temperature 880±20℃;

[0031] 6) Fan opening degree: 1#-5# fans opening degree 100%, 6#-8# fans opening degree 50%;

[0032] 7) The Steyrmo roller speed setting is as follows:

[0033]

[0034] 1. Strictly control the oxygen and nitrogen elements of the casting, as shown in the following table:

[0035]

[0036] Through the implementation of technical solutions 1) 2) 3), the content of the two gas elements was detected to be significantly reduced and stabilized within a fixed range, which played a great role in ensuring the quality of the continuous casting billet.

[0037] 2. The results of constant pulling speed control are shown in the following table:

[0038]

[0039] Through the implementation of technical solution 4), the improved continuous casting billet drawing speed is stably controlled, which basically eliminates the phenomenon of hollow continuous casting billets and prevents the porosity caused by excessive gas content, especially oxygen content, during the continuous casting process.

[0040] 4. The improvement of the stability of the product's mechanical properties is shown in the following table.

[0041]

[0042] Through the implementation of technical solutions 5), 6), and 7), the mechanical properties of the product fully meet the design requirements.

[0043] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A production method of 45# steel, comprising blast furnace molten iron - molten iron pretreatment - converter top and bottom blowing smelting - LF refining - small square billet continuous casting - slow cooling - long product mill rolling; billet heating - high-pressure water descaling - rough rolling - intermediate rolling - finishing rolling - controlled cooling water tank - wire laying - Stelmor cooling - coiling - trimming - sampling inspection - collection and bundling - weighing - finished wire rod; characterized in that: The main production processes include: 1) Gas content requirements for ingot casting: O≤30ppm, N≤60ppm; single slag or double slag operation is adopted according to the molten iron conditions, and the end point basicity is 2.7-3.5; 2) The converter adopts high-drawing supplementary blowing operation, and the final composition of steel tapping is C ≥ 0.10%, T ≥ 1610℃; 3) When tapping steel, strengthen the contact with the tank repairer and perform argon blowing operation according to regulations. Argon control requirements: large argon stirring in the early stage of tapping steel, and when the tapping amount is greater than 2 / 3, reduce the argon flow rate to perform slag blocking operation to ensure that the alloy does not clump and the top slag material is well melted; 4) Starting pulling speed 0.25m / min, target constant pulling speed 2.0m / min; 5) Rolling temperature control: starting rolling temperature 1000±20℃, finishing rolling temperature 920±20℃, spinning temperature 880±20℃; 6) Fan opening degree: 1#-5# fans opening degree 100%, 6#-8# fans opening degree 50%; 7) The Steyrmo roller speed setting is as follows: The chemical composition of the 45# steel is as follows by mass percentage: C: 0.42-0.050%; Si: 0.17-0.37%; Mn: 0.50-0.80%; P≤0.035%; S: ≤0.035%; the remainder is Fe and a small amount of impurity elements.

2. The method for producing 45# steel according to claim 1, characterized in that: When Si≤0.5, single slag operation is adopted for molten iron entering the furnace; when Si>0.5, double slag operation is adopted.

3. The method for producing 45# steel according to claim 1, characterized in that: Gas content requirement for casting billet: O≤28ppm.

4. The method for producing 45# steel according to claim 1, characterized in that: Gas content requirement for casting billet: N≤50ppm.

5. The method for producing 45# steel according to claim 1, characterized in that: The pulling speed fluctuation range is ±0.1m / min.

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