High-carbon steel wire rod for nail shooting and production method

Abstract

The invention relates to the technical field of wire rod production, in particular to a high-carbon steel wire rod for shooting nails, which comprises the following chemical components in percentage by mass: 0.69 to 0.75 percent of C, 0.15 to 0.35 percent of Si, 0.60 to 0.75 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.020 percent of S, less than or equal to 0.020 percent of Cr, less than or equal to 0.010 percent of Ni, less than or equal to 0.010 percent of Cu, less than or equal to 0.040 percent of Mo, 0.020 to 0.050 percent of Al, 0.020 to 0.050 percent of N, less than or equal to 0.0002 percent of H and the balance of Fe and inevitable impurities. The production process comprises the steps of steelmaking, continuous casting, continuous rolling cogging, billet coping and wire rolling. The tensile strength of the finished wire rod is larger than 1000 MPa, the ductility is larger than 12%, the area reduction rate is larger than 30%, the wire rod is not prone to cracking in the stretching and forging process, and meanwhile good toughness is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of wire rod production, and particularly relates to a high-carbon steel wire rod for nail guns and a production method thereof. Background Art

[0002] Nail guns have relatively high strength and toughness, and are generally made of high-carbon steel wire rods. After heat treatment, the core hardness of the finished product is HRC52 - 57, and it can penetrate a Q235 steel plate with a thickness of 0.8 - 1.2 mm. The principle is to use a nail gun to activate a nail gun cartridge, causing the gunpowder in the cartridge to burn and release energy, and directly driving the nail into a hard substrate such as metal, concrete, rock, masonry, etc., for fixing structural fittings such as pipe clamps, pipe brackets, brackets, and eyebolts, solving the situation that nails could not be directly driven into hard substrates in engineering practice for a long time, and having a wide range of applications. The existing wire rods for nail guns have poor plasticity and drawing performance, and it is found that there are reticular cracks on the side of the head during the heading process. This defect not only affects the appearance of the nail gun, but also seriously affects the service life of the nail gun.

[0003] The existing patent CN202210280315.0 is a wire rod for nail guns, a drawn wire for nail guns, a nail gun and a preparation method thereof. The chemical composition of the wire rod for nail guns by mass percentage includes: C: 0.65 - 0.69%, Si: 0.15 - 0.35%, Mn: 0.70 - 0.85%, P: 0.020% and below, S: 0.020% and below, Als: 0.02 - 0.04%, N: 0.006 - 0.01%, Cr: 0.15 - 0.25%, Ti: 0.10% and below, As: 0.02% and below, Sn: 0.028% and below, and the balance is Fe and unavoidable impurities. This patent regulates the contents of Als and N in the chemical composition of the wire rod for nail guns to be 0.02 - 0.04% and 0.006 - 0.01% respectively to improve the plasticity and drawing performance of the wire rod. This wire rod product has problems such as a high cracking rate during cold heading, large fluctuations in the strength of the finished product, and easy fracture of the finished screw during bending. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a production method for a high-carbon steel wire rod for nail guns, in which the wire rod is not easily cracked during stretching and heading, and at the same time has good toughness.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A high-carbon steel wire rod for nail shooting, with the chemical composition by mass percentage as follows: C: 0.69% - 0.75%, Si: 0.15% - 0.35%, Mn: 0.60% - 0.75%, P ≤ 0.020%, S ≤ 0.020%, Cr ≤ 0.020%, Ni ≤ 0.010%, Cu ≤ 0.010%, Mo ≤ 0.040%, Al: 0.020 - 0.050%, N: 0.020 - 0.050%, H ≤ 0.0002%, and the rest being Fe and unavoidable impurities.

[0007] The reasons for setting the ranges of the components are as follows:

[0008] C: C is the element with the most obvious solid-solution strengthening effect in steel, enabling the wire rod and the finished nail for shooting to have sufficient strength. A certain amount of carbon element must be retained in the steel. To improve the strength stability of the finished nail for shooting, the range of C is 0.69 - 0.75%;

[0009] Si: Si is a ferrite solid-solution strengthening element. At the same time, it also causes a sharp increase in the cold heading deformation resistance, significantly increasing the consumption of the die and being unfavorable for cold working plastic deformation. Therefore, the range of Si is 0.15 - 0.35%;

[0010] Mn: Mn plays the roles of solid-solution strengthening and fine-grain strengthening, and delays the transformation of pearlite and ferrite, improving the strength and work-hardening performance of the steel. Therefore, the content of Mn is controlled to be 0.60 - 0.75%;

[0011] P, S: They are harmful elements in steel and should be controlled as low as possible;

[0012] Cr: Cr can improve the strength and toughness of the steel, improve the atmospheric corrosion resistance, and effectively improve the hardenability, ensuring the strength and hardness of the material after quenching. However, as a material for small-sized high-carbon steel nails for shooting, the addition of Cr element will cause the hardenability of the material to increase too much, easily generating harmful structures such as martensite. Therefore, the Cr component is controlled as a residual element, with the range ≤ 0.20%;

[0013] Ni, Cu, Mo are residual elements, which affect the hardenability of this product and cause fluctuations in the performance of the finished product. Therefore, they should all be controlled within a relatively low range, Ni ≤ 0.010%, Cu ≤ 0.010%, Mo ≤ 0.040%;

[0014] Al: Adding a certain content of Al (0.020% - 0.050%) for grain refinement and deoxidation enables the steel to obtain a very low oxygen content, reducing the number and size of non-metallic inclusions in the steel;

[0015] N: It can improve the grain boundary strength, and at the same time combine with Al to form nucleation particles AlN, which has the effects of solution strengthening, improving hardenability, refining grains, and increasing the creep strength of steel; however, if the content of N is too high, it will increase the brittleness of steel, so the content of N is controlled below 0.012%.

[0016] H: During the iron and steel metallurgy process, element H is regarded as one of the extremely harmful elements. The main influence of element H on the properties of steel is to cause hydrogen embrittlement, make the steel become brittle, significantly reduce its ductility and toughness, increase the fracture risk, and at the same time, the diffusion and aggregation of H may also weaken the fatigue performance of the steel, leading to premature failure. Therefore, H should be controlled within a lower range, controlled as H≤0.0002%.

[0017] A production method of high-carbon steel wire rod for nail shooting, the production process includes steelmaking, continuous casting, continuous rolling and blooming, billet grinding, and wire rod rolling; specifically includes:

[0018] 1) Steelmaking: including converter smelting and secondary refining;

[0019] 2) Bloom continuous casting: control the target superheat ≤30°C; the electromagnetic stirring current of the mold ≥400A;

[0020] 3) Continuous rolling and blooming: the heating temperature of the bloom is 1200±100°C, the rolling start temperature is 1150±50°C, and it is rolled into small billets by the blooming mill and transported to the cooling bed for cooling;

[0021] 4) Wire rod rolling:

[0022] ① Billet heating: the billet out-of-furnace temperature is 920±25°C, and the through-strip temperature difference ≤30°C;

[0023] ② Rolling: the finishing mill entry temperature is 925±25°C, the double-module entry temperature is 905±25°C, and the laying head temperature is 910±10°C;

[0024] ③ Use the Stelmor air-cooling line to cool the above-mentioned wire rod. The cooling rate of the wire rod before it cools to 620°C is 10-15°C / s, and the cooling rate of the wire rod after its temperature drops to 620°C ≤10°C / s.

[0025] In step 1), low-sulfur hot metal is used during the smelting process or the hot metal is desulfurized and slagged; slag is blocked during tapping, and the thickness of the slag layer after tapping ≤100mm; a reducing slag is made in the refining LF furnace.

[0026] In step 2), the size of the continuous-cast bloom is 320×410mm.

[0027] In step 3), the size of the small billet is 160×160mm or 140×140mm.

[0028] Compared with the existing technologies, the beneficial effects of the present invention are as follows:

[0029] 1. By regulating the contents of Al and N in the chemical composition of the wire rod for nail shooting to be 0.02 - 0.04% and 0.020 - 0.050% respectively, the present invention improves the plasticity and drawing performance of the wire rod. However, the wire rod products have problems such as high cracking rate during cold heading, large fluctuations in the strength of finished products, and easy fracture of bent finished screws. By increasing the C content and reducing the contents of residual elements such as Cr, Ni, and Mo, the performance stability of the wire rod after heat treatment during user use is improved. At the same time, the risk of generating harmful structures such as martensite during the heat treatment process of the wire rod is reduced, and the plasticity of the final product is improved.

[0030] 2. The tensile strength of the finished wire rod of the present invention is greater than 1000 MPa, the elongation is greater than 12%, and the reduction of area is greater than 30%. The wire rod is not easy to crack during the stretching and forging processes and has good toughness at the same time. The fluctuation of the tensile strength of the nails produced by the wire rod of the present invention is limited within 20 MPa.

[0031] 3. The requirement for the H content is proposed. The H element affects the brittleness of the product. The finished product of this product has a relatively high strength, and the presence of the residual element H increases the risk of brittle fracture of the finished product. This application controls the H content and greatly reduces the risk of brittle fracture of the finished product. The brittle fracture ratio of the nails produced by the wire rod of the present invention is <0.05%;

[0032] 4. The steel billet grinding process improves the surface quality stability of the finished wire rod and reduces the cracking ratio of the nails during user use. The cracking rate of the nails produced by the wire rod of the present invention is reduced to less than 0.5%. Specific Embodiments

[0033] It should be noted that unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field of this patent; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this patent. The mention of "embodiment" in this article means that the specific features, structures or characteristics described in connection with the embodiment may be included in at least one embodiment of this patent. The appearance of this phrase in various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0034] A kind of high-carbon steel wire rod for nail shooting, the mass percentage of chemical components is: C: 0.69% - 0.75%, Si: 0.15% - 0.35%, Mn: 0.60% - 0.75%, P ≤ 0.020%, S ≤ 0.020%, Cr ≤ 0.020%, Ni ≤ 0.010%, Cu ≤ 0.010%, Mo ≤ 0.040%, Al: 0.020 - 0.050%, N: 0.020 - 0.050%, H ≤ 0.0002%, and the rest is Fe and inevitable impurities.

[0035] A production method of high-carbon steel wire rod for nail shooting, the processes include steelmaking, continuous casting, continuous rolling and blooming, billet grinding, and wire rod rolling; specifically including:

[0036] 1) Steelmaking includes converter smelting and LF refining outside the furnace; use low-sulfur hot metal or desulfurize and skim the hot metal; the alloy materials and scrap steel should be kept dry and clean; slagging-off during tapping, and the thickness of the slag layer after tapping ≤ 100mm; the refining LF furnace makes a reducing slag;

[0037] 2) Bloom continuous casting: control the target superheat ≤ 30°C; the electromagnetic stirring current of the mold ≥ 400A; the size of the continuous casting bloom is 320×410mm;

[0038] 3) Continuous rolling and blooming: Check the equipment of each process before production to ensure the quality of the billet; before rolling, check the surface of the rolls, roller table, roll gap, etc. to avoid defects such as ears and scratches in the continuous rolling process; the heating temperature of the bloom is 1200 ± 100°C, the starting rolling temperature is 1150 ± 50°C, and it is rolled into a small square billet of 160mm×160mm by the blooming mill and transported to the cooling bed for cooling; continuous rolling billet identification: apply the melting number with white oil at one end of the billet and the identification at the other end;

[0039] 4) Billet grinding: Detect and locally grind the billet; improve the surface quality stability of the finished wire rod and reduce the cracking ratio of the nails made by users during use;

[0040] 5) Wire rod rolling:

[0041] Billet heating: The billet furnace outlet temperature and the through-strip temperature difference comply with the regulations in Table 1.

[0042] Table 1:

[0043] Billet tapping temperature / °C Temperature difference along the whole length / °C 920±25 ≤30

[0044] The inlet temperature of the wire rod finish rolling, the inlet temperature of the double module, and the spinning temperature should comply with the regulations in Table 2.

[0045] Table 2:

[0046] Temperature at the entrance of finish rolling / °C Temperature at the entrance of double modules / °C Spinning temperature / °C 925±25 905±25 910±10

[0047] The wire rod is cooled by a Stelmor air-cooling line. The roller table speed adopts the fast roller table process, with an initial speed of 0.80 m / s. The cooling speed of the wire rod is controlled by controlling the fan speed. The first 8 fans adopt a large air volume, and the fan speed is 900 - 1000 revolutions, ensuring that the wire rod is cooled to 620 °C before entering the 9th fan. The cooling speed of the wire rod is 10 - 15 °C / s. After the 9th fan and subsequent fans, the fan speed is reduced to control the cooling speed of the wire rod ≤ 10 °C / s. That is, the cooling speed before the wire rod is cooled to 620 °C is 10 - 15 °C / s, and the cooling speed after the temperature of the wire rod drops to 620 °C is ≤ 10 °C / s.

[0048] The air-cooling roller table speed conforms to the provisions of Table 3.

[0049] Table 3:

[0050]

[0051] The air-cooling fan speed conforms to the provisions of Table 4.

[0052] Table 4:

[0053]

[0054] The surface of the wire rod after rolling is inspected, and it is ensured that the defects at the head and tail are trimmed clean.

[0055] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0056] Embodiment:

[0057] The production method of high-carbon steel wire rod A72B-LD with a specification of Φ6.5mm includes the following chemical components by weight percentage, as shown in Table 5.

[0058] Table 5: Chemical Composition (%)

[0059]

[0060]

[0061] The continuous rolling and blooming process is shown in Table 6.

[0062] Table 6: Continuous Rolling and Blooming Process

[0063] Serial number Heating temperature of bloom, °C Rolling start temperature, °C Example 1 1250 1160 Example 2 1210 1180 Example 3 1220 1150 Example 4 1260 1170 Example 5 1240 1150

[0064] The wire rod rolling process is shown in Table 7.

[0065] Table 7: Wire Rod Rolling Process

[0066] Serial number Tapping temperature, °C Temperature at the entrance of finish rolling, °C Temperature at the entrance of double modules, °C Spinning temperature, °C Example 1 933 935 913 912 Example 2 925 932 909 913 Example 3 927 936 912 908 Example 4 930 933 913 915 Example 5 933 929 910 910

[0067] The performance inspection results of the finished wire rod are shown in Table 8.

[0068] Table 8: Performance inspection results

[0069] Serial number Tensile strength, MPa Elongation, % Reduction of area, % Example 1 1033 13 33 Example 2 1045 14 35 Example 3 1021 12.5 32 Example 4 1020 13 33 Example 5 1016 13.5 32

[0070] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high-carbon steel wire rod for nail shooting, characterized in that, The mass percentages of chemical components are as follows: C: 0.69% - 0.75%, Si: 0.15% - 0.35%, Mn: 0.60% - 0.75%, P ≤ 0.020%, S ≤ 0.020%, Cr ≤ 0.020%, Ni ≤ 0.010%, Cu ≤ 0.010%, Mo ≤ 0.040%, Al: 0.020 - 0.050%, N: 0.020 - 0.050%, H ≤ 0.0002%, and the balance is Fe and inevitable impurities.

2. The production method of a high-carbon steel wire rod for nail shooting according to claim 1, characterized in that, The production process includes steelmaking, continuous casting, continuous rolling blooming, bloom grinding, and wire rod rolling; specifically including: 1) Steelmaking includes converter smelting and secondary refining. 2) Bloom continuous casting: The controlled target superheat degree ≤ 30°C; the mold electromagnetic stirring current ≥ 400 A. 3) Continuous rolling blooming: The heating temperature of the bloom is 1200 ± 100°C, the rolling start temperature is 1150 ± 50°C, and it is rolled into small blooms by the blooming mill and then transported to the cooling bed for cooling. 4) Wire rod rolling: ① Bloom heating: The bloom discharging temperature is 920 ± 25°C, and the through-strip temperature difference ≤ 30°C. ② Rolling: The finishing mill inlet temperature is 925 ± 25°C, the double-module inlet temperature is 905 ± 25°C, and the laying head temperature is 910 ± 10°C. ③ The above-mentioned wire rod is cooled by a Stelmor air-cooling line. The cooling rate of the wire rod before it cools to 620°C is 10 - 15°C / s, and the cooling rate of the wire rod after its temperature drops to 620°C ≤ 10°C / s.

3. A method for producing high-carbon steel wire rods for nail shooting according to claim 2, characterized in that, In step 1), low-sulfur hot metal is used during the smelting process or the hot metal is desulfurized and slagged; slag is blocked during tapping, and the thickness of the slag layer after tapping ≤ 100 mm; a reducing slag is made in the refining LF furnace.

4. A production method of high-carbon steel wire rod for nail shooting according to claim 2, characterized in that, In step 2), the size of the continuous-cast bloom is 320 × 410 mm.

5. A production method of high-carbon steel wire rod for nail shooting according to claim 2, characterized in that, In step 3), the size of the small bloom is 160 × 160 mm or 140 × 140 mm.

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