Production method of annealing-free 10.9-grade and above high-strength alloy cold heading steel wire rod

Abstract

The invention belongs to the technical field of metallurgy, and particularly relates to a production method of an annealing-free 10.9-grade and above high-strength alloy cold heading steel wire rod. The cold heading steel wire rod comprises the following chemical components in percentage by weight: 0.32%-0.38% of C, 0.15%-0.30% of Si, 0.60%-0.90% of Mn, less than or equal to 0.020% of P, less than or equal to 0.010% of S, more than or equal to 0.020% of Al, 0.80%-1.10% of Cr, 0.15%-0.30% of Mo and the balance of Fe and inevitable impurities. Comprising the following key process steps: (1) reducing and sizing at the temperature of 780-820 DEG C; (2) the spinning temperature is 760-800 DEG C; (3) the temperature of entering a heat preservation cover is 690-730 DEG C; and (4) the temperature of discharging from a heat insulation cover is not more than 550 DEG The metallographic structure of the obtained cold forging steel is ferrite and pearlite, the specification is phi 5.5-phi 12.0 mm, and the tensile strength is smaller than or equal to 800 MPa. Therefore, the requirements of customers for reducing and avoiding the annealing process are met, and the purposes of saving energy, reducing emission, improving production efficiency and creating benefits for customers are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgy, and in particular to a method for producing annealing-free 10.9-grade and above high-strength alloy cold heading steel wire rods. Background Art

[0002] Cold heading steel is a type of steel that is formed by one or more impact loadings at room temperature. It has very high requirements on the cold forming performance of the material. Cold heading steel has been widely used in the production of standard parts (fasteners) such as bolts, screws, pins, and nuts.

[0003] At present, most domestic steel mills provide medium carbon Cr-Mo cold heading steel (representative grades include ML35CrMo, SCM435, SCM440, 35CrMo, 42CrMo, etc.) and medium carbon Cr cold heading steel (representative grades include ML40Cr, 40Cr, etc.) which are subjected to quenching + tempering heat treatment to produce 10.9 grade and above high strength fastener steel.

[0004] The common production process for high-strength fasteners in existing technology involves cold-forging steel wire rod annealing, pickling and phosphating, drawing, spheroidizing annealing, cold-forging, quenching and tempering heat treatment, surface treatment, and packaging. To ensure the material's cold-forging performance, spheroidizing annealing is typically required in this fastener manufacturing process.

[0005] In response to the country's call for energy conservation and emission reduction, the heat treatment process of parts manufacturing enterprises is the main energy consumption link. Therefore, reducing the heat treatment process can significantly reduce energy consumption and carbon emissions. At the same time, omitting the annealing process can also shorten the processing steps and effectively improve production efficiency.

[0006] Small-scale, high-strength alloy cold-heading steels, due to their small size and rapid cooling rates, present significant challenges in controlling their metallographic structure and properties. Improving the cold-heading performance of these small-scale, high-strength alloy cold-heading steels is an urgent challenge. Therefore, research and development of technologies to control the production of small-scale, high-strength alloys is crucial. Summary of the Invention

[0007] To achieve the above-mentioned purpose, the present invention provides a method for producing annealing-free 10.9 grade and above high-strength alloy cold heading steel wire rod. The key of the present invention is to obtain the metallographic structure required for small-size high-strength alloy cold heading steel by controlling rolling and cooling, thereby reducing the tensile strength to meet the customer's requirements for reducing or exempting annealing process, thereby achieving the purpose of energy conservation and emission reduction, improving production efficiency, and creating benefits.

[0008] The present invention adopts the following technical solutions:

[0009] A method for producing annealing-free 10.9 grade and above high-strength alloy cold-heading steel wire rod, characterized in that the chemical composition of the cold-heading steel wire rod is as follows by weight: C: 0.32% to 0.38%, Si: 0.15% to 0.30%, Mn: 0.60% to 0.90%, P≤0.020%, S≤0.010%, Al≥0.020%, Cr: 0.80% to 1.10%, Mo: 0.15% to 0.30%, and the remainder is Fe and unavoidable impurities; the method comprises the following key process steps:

[0010] (1) Sizing temperature: 780-820℃;

[0011] (2) Spinning temperature: 760-800℃;

[0012] (3) Temperature entering the heat preservation cover: 690-730℃

[0013] (4) The temperature out of the insulation cover is ≤550℃.

[0014] Furthermore, the chemical composition of the cold heading steel wire rod is as follows by weight: C: 0.35%, Si: 0.21%, Mn: 0.69%, P: 0.012%, S: 0.003%, Al: 0.028%, Cr: 0.91%, Mo: 0.16%, and the rest is Fe and unavoidable impurities.

[0015] Furthermore, the chemical composition of the cold heading steel wire rod is as follows by weight: C: 0.36%, Si: 0.22%, Mn: 0.70%, P: 0.011%, S: 0.004%, Al: 0.027%, Cr: 0.91%, Mo: 0.16%, and the rest is Fe and unavoidable impurities.

[0016] Furthermore, in step (4), the roller speed is 0.10-0.45 m / s.

[0017] Furthermore, the temperature entering the sizing process is 798°C, the spinning temperature is 782°C, the temperature entering the heat preservation hood is 702°C, and the temperature exiting the heat preservation hood is 548°C.

[0018] Furthermore, the temperature before entering the sizing process is 818°C, the spinning temperature is 773°C, the temperature before entering the heat preservation hood is 712°C, and the temperature before exiting the heat preservation hood is 545°C.

[0019] Furthermore, the temperature before entering the sizing process is 795°C, the spinning temperature is 772°C, the temperature before entering the heat preservation hood is 706°C, and the temperature before exiting the heat preservation hood is 540°C.

[0020] Furthermore, the metallographic structure of the cold heading steel is ferrite + pearlite, the specification is φ5.5-φ12.0mm, and the tensile strength is ≤800MPa.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention obtains the ferrite + pearlite metallographic structure required for small-size high-strength alloy cold heading steel by controlling rolling and cooling, and reduces the tensile strength (≤800MPa), meeting the customer's requirements for reducing or exempting annealing process, thereby achieving the purpose of energy conservation and emission reduction, improving production efficiency, and creating benefits for customers. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 This is the metallographic structure diagram of the wire rod in Example 1;

[0025] Figure 2 This is the metallographic structure diagram of the wire rod in Example 2;

[0026] Figure 3 This is the metallographic structure diagram of the wire rod in Example 3;

[0027] Figure 4 This is the metallographic structure diagram of the wire rod of comparative example 1;

[0028] Figure 5 This is the metallographic structure diagram of the wire rod of comparative example 2. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0030] Example 1:

[0031] A method for producing annealing-free, grade 10.9 and above high-strength alloy cold-heading steel wire rod, with a rolling specification of Φ5.5 mm. As shown in Table 1, the chemical composition of the cold-heading steel wire rod is, by weight, C: 0.35%, Si: 0.21%, Mn: 0.69%, P: 0.012%, S: 0.003%, Al: 0.028%, Cr: 0.91%, Mo: 0.16%, with the remainder being Fe and unavoidable impurities. Tests were conducted according to the following process steps:

[0032] The 150 square steel billet enters the heating furnace for three-stage heating. The time in the furnace is 102 minutes, and the temperature out of the furnace is 1010℃. After 6 passes of initial rolling, 6 passes of intermediate rolling, 6 passes of pre-finishing rolling and 10 passes of finishing rolling, the temperature entering the reducing and sizing unit is 798℃; after 4 passes of rolling through the reducing and sizing unit, it enters the wire laying head with a wire laying temperature of 782℃; the temperature entering the insulation cover is 702℃, the roller speed is 0.10-0.40m / s, and the temperature out of the insulation cover is 548℃.

[0033] The mechanical properties of the wire rod (8 pieces) produced by the above composition and process are 751-795MPa, and the metallographic structure is ferrite + pearlite. Figure 1 shown.

[0034] Example 2:

[0035] A method for producing annealing-free, grade 10.9 and above high-strength alloy cold-heading steel wire rod, with a rolling specification of Φ8.0 mm. As shown in Table 1, the chemical composition of the cold-heading steel wire rod is, by weight, C: 0.36%, Si: 0.22%, Mn: 0.70%, P: 0.011%, S: 0.004%, Al: 0.027%, Cr: 0.91%, Mo: 0.16%, with the remainder being Fe and unavoidable impurities. Tests were conducted according to the following process steps:

[0036] The 150 square steel billet enters the heating furnace for three-stage heating. The time in the furnace is 108 minutes, and the temperature out of the furnace is 1005℃. After 6 passes of initial rolling, 6 passes of intermediate rolling, 6 passes of pre-finishing rolling, and 10 passes of finishing rolling, the temperature entering the reducing and sizing unit is 818℃; after 4 passes of rolling through the reducing and sizing unit, it enters the wire laying head, and the wire laying temperature is 773℃; the temperature entering the insulation cover is 712℃, the roller speed is 0.11-0.42m / s, and the temperature out of the insulation cover is 545℃.

[0037] The mechanical properties of the wire rod (8 pieces) produced by the above composition and process are 721-778MPa, and the metallographic structure is ferrite + pearlite. Figure 2 shown.

[0038] Example 3:

[0039] A method for producing annealing-free, grade 10.9 and above high-strength alloy cold-heading steel wire rod, with a rolling specification of Φ12.0 mm. As shown in Table 1, the chemical composition of the cold-heading steel wire rod is, by weight, C: 0.35%, Si: 0.20%, Mn: 0.68%, P: 0.013%, S: 0.003%, Al: 0.026%, Cr: 0.93%, Mo: 0.16%, with the remainder being Fe and unavoidable impurities. Tests were conducted according to the following process steps:

[0040] The 150 square steel billet enters the heating furnace for three-stage heating. The time in the furnace is 105 minutes, and the temperature out of the furnace is 1003℃. After 6 passes of initial rolling, 6 passes of intermediate rolling, 6 passes of pre-finishing rolling and 10 passes of finishing rolling, the temperature entering the reducing and sizing unit is 795℃; after 4 passes of rolling through the reducing and sizing unit, it enters the wire laying head with a wire laying temperature of 772℃; the temperature entering the insulation cover is 706℃, the roller speed is 0.12-0.45m / s, and the temperature out of the insulation cover is 540℃.

[0041] The mechanical properties of the wire rod (8 pieces) produced by the above composition and process are 698-732MPa, and the metallographic structure is ferrite + pearlite. Figure 3 shown.

[0042] Comparative Example 1:

[0043] A method for producing annealing-free, grade 10.9 and above high-strength alloy cold-heading steel wire rod, with a rolling specification of Φ6.5 mm. As shown in Table 1, the chemical composition of the cold-heading steel wire rod is, by weight, 0.35% C, 0.20% Si, 0.68% Mn, 0.013% P, 0.003% S, 0.026% Al, 0.93% Cr, 0.16% Mo, with the remainder being Fe and unavoidable impurities. Tests were conducted according to the following process steps:

[0044] The 150 square steel billet enters the heating furnace for three-stage heating. The time in the furnace is 107 minutes, and the temperature out of the furnace is 1006℃. After 6 passes of initial rolling, 6 passes of intermediate rolling, 6 passes of pre-finishing rolling and 10 passes of finishing rolling, the temperature entering the reducing and sizing unit is 890℃; after 4 passes of rolling through the reducing and sizing unit, it enters the wire laying head with a wire laying temperature of 910℃; the temperature entering the insulation cover is 710℃ (the front insulation cover is turned on), the roller speed is 0.10-0.40m / s, and the temperature out of the insulation cover is 560℃.

[0045] The mechanical properties of the wire rod (8 pieces) produced by the above composition and process are 866-1032MPa, and the metallographic structure is bainite + a small amount of ferrite. Figure 4 shown.

[0046] Comparative Example 2:

[0047] A method for producing annealing-free, grade 10.9 and above high-strength alloy cold-heading steel wire rod, with a rolling specification of Φ12.0 mm. The chemical composition of the cold-heading steel wire rod is as follows by weight: C: 0.34%, Si: 0.21%, Mn: 0.69%, P: 0.013%, S: 0.003%, Al: 0.029%, Cr: 0.92%, Mo: 0.16%, with the remainder being Fe and unavoidable impurities. Tests were conducted according to the following process steps:

[0048] The 150 square steel billet is heated in three stages in the heating furnace. The time in the furnace is 100 minutes and the temperature out of the furnace is 1002℃. After 6 passes of initial rolling, 6 passes of intermediate rolling, 6 passes of pre-finishing rolling and 10 passes of finishing rolling, the temperature of the billet entering the reducing and sizing unit is 805℃. After 4 passes of rolling through the reducing and sizing unit, the billet enters the wire laying head with a wire laying temperature of 795℃; the temperature entering the insulation cover is 765℃, the roller speed is 0.20-0.50m / s, and the temperature out of the insulation cover is 640℃.

[0049] The mechanical properties of the wire rod (8 pieces) produced by the above composition and process are 805-912MPa, and the metallographic structure is bainite + ferrite + pearlite. Figure 5 shown.

[0050] Table 1 Chemical composition of steels in various embodiments and comparative examples (wt.%)

[0051] chemical composition C Si Mn P S Al Cr Mo Example 1 0.35 0.21 0.69 0.012 0.003 0.028 0.91 0.16 Example 2 0.36 0.22 0.70 0.011 0.004 0.027 0.91 0.16 Example 3 0.35 0.20 0.68 0.013 0.003 0.026 0.93 0.16 Comparative Example 1 0.35 0.20 0.68 0.013 0.003 0.026 0.93 0.16 Comparative Example 2 0.34 0.21 0.69 0.013 0.003 0.029 0.92 0.16

[0052] Table 2 Temperature of relevant steps in each experimental example

[0053]

[0054]

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention are included in the scope of protection of the present invention.

Claims

1. A method for producing annealing-free 10.9 grade and above high-strength alloy cold heading steel wire rod, characterized in that: The chemical composition of the cold heading steel wire rod is as follows by weight: C: 0.32% to 0.38%, Si: 0.15% to 0.30%, Mn: 0.60% to 0.90%, P≤0.020%, S≤0.010%, Al≥0.020%, Cr: 0.80% to 1.10%, Mo: 0.15% to 0.30%, and the rest is Fe and unavoidable impurities; The key process steps include: (1) Sizing temperature: 780-820℃; (2) Silk spinning temperature: 760-800℃; (3) Temperature entering the heat preservation hood: 690-730℃; (4) The temperature out of the insulation cover is ≤550℃.

2. The method for producing annealing-free 10.9 grade and above high-strength alloy cold heading steel wire rod as claimed in claim 1, characterized in that: The chemical composition of the cold heading steel wire rod is as follows by weight: C: 0.35%, Si: 0.21%, Mn: 0.69%, P: 0.012%, S: 0.003%, Al: 0.028%, Cr: 0.91%, Mo: 0.16%, and the rest is Fe and unavoidable impurities.

3. The method for producing annealing-free 10.9 grade and above high-strength alloy cold heading steel wire rod as claimed in claim 1, characterized in that: The chemical composition of the cold heading steel wire rod is as follows by weight: C: 0.36%, Si: 0.22%, Mn: 0.70%, P: 0.011%, S: 0.004%, Al: 0.027%, Cr: 0.91%, Mo: 0.16%, and the rest is Fe and unavoidable impurities.

4. The method for producing annealing-free 10.9 grade and above high-strength alloy cold heading steel wire rod as claimed in claim 1, characterized in that: The chemical composition of the cold heading steel wire rod is as follows by weight: C: 0.35%, Si: 0.20%, Mn: 0.68%, P: 0.013%, S: 0.003%, Al: 0.026%, Cr: 0.93%, Mo: 0.16%, and the rest is Fe and unavoidable impurities.

5. The method for producing annealing-free 10.9 grade and above high-strength alloy cold heading steel wire rod as claimed in claim 1, characterized in that: In step (4), the roller speed is 0.10-0.45 m / s.

6. A method for producing annealing-free 10.9 grade and above high-strength alloy cold heading steel wire rod as claimed in any one of claims 2 to 4, characterized in that: The temperature entering the sizing process is 798°C, the spinning temperature is 782°C; the temperature entering the insulation cover is 702°C, and the temperature exiting the insulation cover is 548°C.

7. A method for producing annealing-free 10.9 grade and above high-strength alloy cold heading steel wire rod as claimed in any one of claims 2 to 4, characterized in that: The temperature entering the sizing device is 818℃, the spinning temperature is 773℃; the temperature entering the insulation cover is 712℃, and the temperature leaving the insulation cover is 545℃.

8. A method for producing annealing-free 10.9 grade and above high-strength alloy cold heading steel wire rod as claimed in any one of claims 2 to 4, characterized in that: The inlet sizing temperature is 795℃, the spinning temperature is 772℃; the inlet temperature is 706℃, and the outlet temperature is 540℃.

9. A method for producing annealing-free 10.9 grade and above high-strength alloy cold heading steel wire rod as claimed in any one of claims 2 to 4, characterized in that: The cold heading steel has a metallographic structure of ferrite + pearlite, a specification of φ5.5-φ12.0 mm, and a tensile strength of ≤800 MPa.

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