CN111375649A - Preparation method of automobile fastener wire - Google Patents

Preparation method of automobile fastener wire Download PDF

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Publication number
CN111375649A
CN111375649A CN201811634655.9A CN201811634655A CN111375649A CN 111375649 A CN111375649 A CN 111375649A CN 201811634655 A CN201811634655 A CN 201811634655A CN 111375649 A CN111375649 A CN 111375649A
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CN
China
Prior art keywords
product
wire rod
spheroidizing annealing
alloy steel
low
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CN201811634655.9A
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Chinese (zh)
Inventor
肖杰
徐福生
罗安武
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Dongguan Kelee Wire & Technologies Co ltd
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Dongguan Kelee Wire & Technologies Co ltd
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Priority to CN201811634655.9A priority Critical patent/CN111375649A/en
Publication of CN111375649A publication Critical patent/CN111375649A/en
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B21MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21CMANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
    • B21C37/00Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
    • B21C37/04Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of bars or wire
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/06Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C21D8/065Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/02Ferrous alloys, e.g. steel alloys containing silicon
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/04Ferrous alloys, e.g. steel alloys containing manganese
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/32Ferrous alloys, e.g. steel alloys containing chromium with boron
    • CCHEMISTRY; METALLURGY
    • C23COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23CCOATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/05Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
    • C23C22/06Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
    • C23C22/07Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing phosphates
    • C23C22/08Orthophosphates
    • C23C22/12Orthophosphates containing zinc cations
    • C23C22/13Orthophosphates containing zinc cations containing also nitrate or nitrite anions

Abstract

The invention belongs to the technical field of automobile manufacturing, and particularly relates to a preparation method of an automobile fastener wire. The preparation method provided by the invention comprises the following steps: providing a low-carbon alloy steel wire rod, wherein the carbon content of the low-carbon alloy steel wire rod is 0.19-0.21 wt%, and the boron content is 0.0005-0.0030 wt%; sequentially carrying out acid pickling and phosphating on the low-carbon alloy steel wire, and then carrying out first drawing treatment to obtain a first drawing product; carrying out spheroidizing annealing treatment on the first drawing product to obtain a spheroidizing annealing product; the spheroidizing annealing treatment comprises the following steps: heating the first drawing product to 710-730 ℃ under the protective atmosphere, and preserving the heat for 5-8 hours; then cooling to 540-560 ℃ at a speed of 20 ℃/hour, then continuously cooling to 390-410 ℃ at a speed of 80 ℃/hour, and then naturally cooling to the normal temperature; when the temperature is above 550 ℃, the protective atmosphere is methanol cracking gas, and when the temperature in the furnace is less than 550 ℃, the protective atmosphere is nitrogen; sequentially carrying out acid washing and phosphorization on the spheroidizing annealing product, and carrying out second drawing treatment; sodium nitrite is used as an accelerating agent in the phosphorization.

Description

Preparation method of automobile fastener wire
Technical Field
The invention belongs to the technical field of automobile manufacturing, and particularly relates to a preparation method of an automobile fastener wire.
Background
The fastener is widely applied to the fields of automobiles, engineering, buildings and the like, and is called as 'industrial rice' and 'screw' of national economy from the development of the whole manufacturing industry. For example, in the structure of an automotive product, although the fastener occupies only a small part of the whole structure, it is one of the indispensable organic components in the structure of an automotive product, and plays an important role. Common fasteners include bolts, screws, studs, nuts, and combinations thereof such as washers, collars, pins, rivets, connection pairs, and the like. The types of automotive fasteners are various and mainly divided into four main categories, including standard fasteners, non-standard fasteners, standard mechanical elements and non-standard mechanical elements, wherein the quality requirement of the non-standard fasteners is the highest. Among non-standard fasteners, such as connecting rod bolts, flywheel bolts, wheel bolts, suspension bolts and the like of automobile engines, the requirements for high quality and good stability of the non-standard fasteners cannot meet the requirements for localization in China at present, and most of the non-standard fasteners depend on imports.
In the automobile industry, the quantity of the required quantity of cars is the largest, the quantity of the required quantity of fastening pieces in the cars is increased, the quality requirement of the fastening pieces of the cars is very strict, the strength requirements of the fastening pieces of the rods and the fastening pieces of the nuts are mostly more than 8 grades, the product structure is greatly changed, according to statistics, the quantity of the fastening pieces used by one medium-sized commercial vehicle reaches more than two thousand, and the total material consumption quantity of the medium-sized commercial vehicle reaches up to 100kg by adding other connecting accessories. The strength of the fasteners used for the automobile engine of the commercial vehicle is required to reach more than 10 grades, and the strength of the fasteners at other parts is required to reach more than 8 grades. By taking passenger cars as an example, the high-grade brands of cars introduced in China account for over 80 percent, and although the high-grade brands of cars are assembled on the production line in China, most of fasteners used on the cars are directly introduced from abroad. Therefore, the production level of the domestic automobile fasteners is far from the advanced level abroad.
At present, automobile fasteners produced in China have various problems, such as low strength and low toughness, easy cracking during cold heading forming and the like, and the production requirements of high-end automobile fasteners on high strength and high toughness cannot be met.
Disclosure of Invention
The invention mainly aims to provide a preparation method of an automobile fastener wire rod, and aims to provide an automobile fastener with high strength, high toughness and high yield.
In order to achieve the above object, the invention provides a method for preparing an automotive fastener wire, comprising the following steps:
providing a low carbon alloy steel wire having a carbon content of 0.19 wt% to 0.21 wt%, a boron content of 0.0005 wt% to 0.0030 wt%, a sulfur content of 0.025 wt% or less, and a phosphorus content of 0.025 wt% or less;
sequentially carrying out acid pickling and phosphating on the low-carbon alloy steel wire rod, and then carrying out first drawing treatment to obtain a first drawing product;
carrying out spheroidizing annealing treatment on the first drawing product to obtain a spheroidizing annealing product; the spheroidizing annealing treatment comprises the following steps: under the protective atmosphere, heating the first drawing product to 710-730 ℃, and preserving heat for 5-8 hours; then cooling to 540-560 ℃ at a speed of 15-25 ℃/h, then continuously cooling to 390-410 ℃ at a speed of 75-85 ℃/h, and then naturally cooling to normal temperature; when the temperature is above 550 ℃, the protective atmosphere is methanol cracking gas, and when the temperature is less than 550 ℃, the protective atmosphere is nitrogen;
sequentially carrying out acid washing and phosphorization on the spheroidizing annealing product, and then carrying out second drawing treatment to obtain the spheroidizing annealing product;
wherein, sodium nitrite is adopted as an accelerating agent in the phosphorization.
Compared with the prior art, on one hand, the low-carbon alloy steel wire with the boron content of 0.0005 wt% -0.0030 wt% is selected as the raw material, the hardenability and the plastic deformation capacity of the product are improved, the heat treatment performance of the wire is improved to a greater extent, and the product is prevented from brittle fracture under the 8.8-level strength by controlling the content of the boron element and having good toughness and strength; on the other hand, by further process optimization of spheroidizing annealing treatment, a good spheroidized structure is ensured to be obtained after heat treatment, the plastic deformation capacity of the wire rod is further improved, the product is easy to cold heading and form, the yield of the product is improved, meanwhile, a good structure is provided for heat treatment of subsequent products, and the performance of the final product is stable; in the invention, sodium nitrite is used as an accelerating agent in the phosphating process, so that the film forming speed is improved, the formation of a phosphating film with thin and compact film thickness and fine and compact crystal grains is promoted, and the surface quality of a product is ensured.
Detailed Description
In order to provide an automobile fastener with high strength, high toughness and high yield so as to meet the production requirement of domestic high-grade brands of automobiles, the embodiment of the invention provides a preparation method of an automobile fastener wire.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
On one hand, the embodiment of the invention provides a preparation method of an automobile fastener wire, which comprises the following steps:
s01, providing a low-carbon alloy steel wire, wherein the low-carbon alloy steel wire has a carbon content of 0.19 wt% -0.21 wt%, a boron content of 0.0005 wt% -0.0030 wt%, a sulfur content of 0.025 wt% or less, and a phosphorus content of 0.025 wt% or less;
s02, sequentially carrying out acid washing and phosphating on the low-carbon alloy steel wire rod, and then carrying out first drawing treatment to obtain a first drawing product;
s03, performing spheroidizing annealing treatment on the first drawing product to obtain a spheroidizing annealing product; the spheroidizing annealing treatment comprises the following steps: under the protective atmosphere, heating the first drawing product to 710-730 ℃, and preserving heat for 5-8 hours; then cooling to 540-560 ℃ at a speed of 15-25 ℃/h, then continuously cooling to 390-410 ℃ at a speed of 75-85 ℃/h, and then naturally cooling to normal temperature; when the temperature is above 550 ℃, the protective atmosphere is methanol cracking gas, and when the temperature is less than 550 ℃, the protective atmosphere is nitrogen;
s04, sequentially carrying out acid washing and phosphorization on the spheroidized annealing product, and then carrying out second drawing treatment to obtain the spheroidized annealing product;
wherein, sodium nitrite is adopted as an accelerating agent in the phosphorization.
Specifically, in step S01, the low carbon alloy steel wire rod has a carbon content of 0.19 wt% to 0.21 wt% and a boron content of 0.0005 wt% to 0.0030 wt%. The boron element with the weight percentage of 0.0005 to 0.0030 percent is added into the material with the carbon content of 0.19 to 0.21 percent, so that the heat treatment performance of the product can be improved to a great extent, and the requirement of 8.8 grade can be met.
In the practical research process, the strength of the wire rod is lower after heat treatment when the carbon content is lower than 0.19 wt%, and the strength of the wire rod cannot reach 8.8 grade; when the carbon content is higher than 0.21 wt%, the wire rod has higher hardness and poor shaping after heat treatment, is easy to crack after cold heading forming, and has low forming rate.
The addition of boron element in the material with carbon content of 0.19-0.21 wt% can raise the hardenability and plastic deformation capacity of the product and improve the heat treatment performance of the wire rod to a great extent. The content of the boron element is controlled to be 0.0005 wt% -0.0030 wt%, so that the wire rod has good toughness and strength after heat treatment, and the product is ensured not to be brittle under 8.8-grade strength.
The addition of 0.0005 to 0.0030 wt% of boron element corresponds to the addition of 0.6 wt% of manganese, 0.7 wt% of chromium, 0.5 wt% of molybdenum and 1.5 wt% of nickel, respectively, and the hardenability of boron element is several times or several tens times higher than that of the above-mentioned alloy elements. According to the scheme of the invention, only a very small amount of boron is added into the wire rod with the carbon content, so that a large amount of precious metal alloy elements can be saved, and the production cost is greatly reduced.
In general, the content of boron added to the wire rod is controlled to be 0.0005 wt% to 0.0030 wt%, and it is disadvantageous to increase hardenability because of excessive or insufficient boron. In the content range, parts with larger sections can be fully quenched, and uniform low-carbon martensite with excellent comprehensive mechanical properties can be obtained in a quenched and tempered state.
Preferably, the content of the boron element is 0.0020 wt% to 0.0025 wt%. Within the content range, the quenched and tempered alloy steel can obtain better matching of strength and toughness, and the brittle fracture of the product is avoided under the strength of 8.8 grade.
In the embodiment of the invention, the sulfur content of the low-carbon alloy steel wire is less than or equal to 0.025 wt%, and the phosphorus content of the low-carbon alloy steel wire is less than or equal to 0.025 wt%. The presence of S, P elements in the material can cause segregation along grain boundaries, resulting in embrittlement of the grain boundaries and impairment of the mechanical properties of the steel. The content of S, P is controlled to be less than or equal to 0.025 wt%, so that the purity of steel can be effectively ensured, nonmetallic inclusions are reduced, and the product is ensured not to crack during cold heading forming. The weight content range of the sulfur and phosphorus elements is matched with the weight content range of the carbon and the boron, so that the cracking probability of the wire rod after heating treatment can be further reduced, and the yield of the wire rod can be synergistically improved.
The mechanical properties of the wire are closely related to the chemical composition, and the microstructure of the wire has a great influence on the mechanical properties, so that the microstructure of the wire needs to be considered when selecting raw materials. The martensite form of the product after heat treatment can be directly influenced by factors such as the grain size of the wire rod, non-metallic inclusions, the existence of widmannstatten structures and the like, and the adverse phenomena of reduction of the mechanical property of the wire rod, cracking of the product and the like are caused.
Preferably, the grain size of the low-carbon alloy steel wire rod is 9-10 grades, the non-metallic inclusion is less than or equal to 1 grade, and the low-carbon alloy steel wire rod does not contain Widmannstatten structures.
Preferably, the ovality of the low-carbon alloy steel wire rod is less than or equal to 0.20 mm. The ovality of the wire is too large, so that the stress is not uniform during drawing deformation, the deformation degree of the internal structure of the material is inconsistent, the performance structure of the drawn material is not uniform, different internal stresses exist, and the subsequent product is easy to crack during heat treatment.
In step S02, the low-carbon alloy steel wire rod is sequentially subjected to acid pickling and phosphating, and surface treatment is performed on the wire rod before drawing treatment, so that a good lubricating effect and good rust-proof performance can be achieved.
Too high or too low concentration of the hydrochloric acid aqueous solution and too long or too short pickling time can affect the surface quality of the product. In one embodiment, the acid washing is performed by using a hydrochloric acid aqueous solution, and the mass concentration of the hydrochloric acid aqueous solution is 10-15%. In another embodiment of the present invention, the pickling time is 15 to 20 min.
And (2) phosphating, namely forming a phosphating film on the surface of the product, wherein the phosphating film can make the surface of the wire more wear-resistant, increase the drawing lubricity and improve the corrosion resistance of the wire. The porous structure of the phosphating film can increase the storage capacity of lubricating grease on the surface of the wire rod, reduce friction factors to promote drawing, delay the occurrence of fretting damage on the surface of the wire rod and inhibit the initiation of fatigue microcracks, thereby greatly prolonging the service life of the wire rod. And phosphating is carried out after acid cleaning, so that the corrosion of the acid liquor to the surface of the wire rod can be prevented, and the surface quality and the quality stability of the wire rod are ensured.
In the embodiment of the invention, sodium nitrite is used as an accelerating agent in the phosphorization. In the prior art, phosphating solution is adopted for phosphating, and the phosphating solution contains an accelerant, and the accelerant is generally more than one. According to the embodiment of the invention, sodium nitrite is selected as the accelerator, so that the growth kinetic condition of a phosphating film manager can be changed, the phosphating film forming speed is accelerated, and meanwhile, a phosphating film with finer and more compact crystal grains is generated, the binding force is stronger, and the phosphating film is not easy to fall off during drawing.
In one embodiment, the phosphating solution used comprises zinc oxide, phosphoric acid and an accelerator, and the accelerator is sodium nitrite. The thickness of the phosphorized film formed after phosphorization is 5-8 mu m.
In another embodiment, the phosphating is followed by saponification. Specifically, the saponification process comprises the following steps: and (3) soaking the phosphatized wire in a sodium stearate solution at the saponification temperature of 80-85 ℃ for 2-3 min. The saponification process forms a composite structure with a film layer of a phosphating film and a saponification film, and the layers are mutually permeated and have good binding force so as to further improve the surface quality of the wire rod, improve the surface lubrication degree of the wire rod and promote the drawing treatment.
Preferably, the temperature of the phosphorization is 70-80 ℃, and the time is 8-10 minutes.
Preferably, the total acidity of the phosphorization is 20-30.
At least any one of low total acidity, low phosphating temperature and short phosphating time can cause a formed phosphating film to be thin and cannot play roles of rust prevention and lubrication; at least any one of high full acidity, high temperature and long phosphating time can cause coarse grains of a phosphating film formed by the phosphating film, the thickness of the phosphating film is poor, the bonding force with the surface layer of a wire rod is poor, the wire rod is easy to fall off in the drawing and forming processes, the lubricating effect cannot be realized, the service life of a die is short, and the surface of a product is damaged by pulling.
Through the optimized phosphating process, phosphating temperature and phosphating time, the automobile fastener wire rod disclosed by the embodiment of the invention has the advantages of high surface smoothness, complete, compact and firm coverage of a phosphating film coating, good lubricating effect, short phosphating treatment time in the production process, energy conservation, no phosphate slag and environmental friendliness, and meets the requirements of a high-speed drawing process and high-deformation product forming.
And carrying out first drawing treatment for carrying out rough drawing on the wire rod, providing preparation for subsequent spheroidizing annealing treatment and obtaining the wire rod with uniform tissue. In one embodiment, the total compression ratio of the first drawing process is equal to or greater than 50%, and the partial compression ratio is equal to or less than 15%.
In step S03, the first drawn product is subjected to spheroidizing annealing. The main purpose of spheroidizing annealing is to spheroidize carbide in the microstructure of the steel material, reduce the hardness of the material, improve the plasticity of the material, reduce the deformation resistance of the material and make the material easy to be plastically processed and formed.
In an embodiment of the present invention, the spheroidizing annealing treatment includes: under the protective atmosphere, heating the first drawing product to 710-730 ℃, and preserving heat for 5-8 hours; then cooling to 540-560 ℃ at the speed of 20 ℃/hour, then continuously cooling to 390-410 ℃ at the speed of 80 ℃/hour, and then naturally cooling to the normal temperature outside the furnace. In the whole spheroidizing annealing process, the key point is the control of the temperature, and the spheroidizing rate of the wire rod is influenced by over-high or over-low temperature.
Further, in the spheroidizing annealing process, if oxygen is contained in the reaction system, the wire rod is easy to react with the oxygen at a high temperature to generate decarburization behavior. When the wire rod is decarburized, the hardness and strength thereof are lowered. In order to protect the wire rod from decarburization, the spheroidizing annealing treatment of the embodiment of the present invention is performed in an oxygen-free environment as much as possible. In one embodiment, the protective atmosphere is methanol cracking gas when the temperature is above 550 ℃, and the protective atmosphere is nitrogen when the temperature in the furnace is less than 550 ℃. Specifically, before the temperature is increased to 550 ℃, nitrogen is filled into the furnace, a large amount of oxygen is discharged and treated, and when the temperature is increased to 550 ℃, for example, the methanol cracking gas is switched into the methanol cracking gas through pipeline filling and valve control, so that a trace amount of oxygen in the furnace and the methanol cracking gas generate chemical reaction, and finally, the atmosphere in the heat treatment furnace is reduced, and the wire is ensured not to be decarburized.
In another embodiment, the flow rate of the nitrogen is 5-10L/min, and the flow rate of the methanol cracking gas is 3-5L/min. The protective atmosphere setting mode of the embodiment of the invention can ensure that the wire rod does not generate decarburization reaction in the spheroidizing annealing treatment process under the gas flow range, and ensure the wire rod processing quality.
Through the optimized spheroidizing annealing temperature and time and the optimized protective atmosphere condition, the automobile fastener wire rod provided by the embodiment of the invention has the advantages of optimal spheroidizing effect, high toughness and high strength, and is suitable for preparing high-grade automobile fasteners.
Through experimental detection, the spheroidization grade of the spheroidization annealing product obtained in the step S03 is more than or equal to grade 5, the grain size is more than or equal to grade 11, the crystal grains are uniformly distributed, the spheroidization rate is high, abnormal structures such as coarse crystal grains and Widmannstatten structures are avoided, the depth of a decarburized layer is less than or equal to 1 percent of the diameter of the automobile fastener wire, the elongation at break is 25 to 30 percent, and the reduction of area is 75 to 80 percent.
In step S04, the spheroidizing annealing product is sequentially subjected to acid washing and phosphating, an oxide layer on the wire rod surface after spheroidizing annealing treatment is removed by the acid washing, and the corrosion resistance of the wire rod is improved by the phosphating, so that the surface quality of the product is ensured, and the stability of the product is ensured.
And performing second drawing treatment for fine drawing of the wire rod to maintain the mechanical stability and dimensional stability of the product. Specifically, the drawing process employs a wire-drawing die. The embodiment of the present invention does not specifically limit the specific structure type of the die, and the die may be a commercially available die, or a die modified by a person skilled in the art by a conventional technique, and the die may have a specific sizing band length and a specific working cone angle, and a specific die hole type.
Through the optimized process, the automobile fastener wire rod provided by the embodiment of the invention has excellent hardenability and good plastic deformation capacity, is suitable for subsequent plastic processing and forming, reaches 8.8-grade standard after heat treatment, ensures that the product is not cracked during cold heading forming, and has high yield.
The automotive fastener wire is subjected to plastic working molding such as: the automobile fastener with high strength and high toughness can be obtained by heating treatment and cold heading forming. The detection result shows that the standard reaches 8.8 grades. Therefore, the automobile fastener wire rod provided by the embodiment of the invention has various performances obviously superior to those of similar products in the current market, can be better applied to the automobile fastener processing industry, improves the service performance and service life of products produced in the fastener industry, has a good market prospect, and creates considerable economic benefits for companies.
In order that the details of the above-described practice and operation of the invention will be clearly understood by those skilled in the art, and the improved performance of the method of making an automotive fastener wire of the present invention embodiment will be apparent, the practice of the invention will now be exemplified by the following examples.
Example 1
The embodiment provides a preparation method of an automobile fastener wire, which comprises the following steps:
s11, providing a low carbon alloy steel wire rod, the composition of which is shown in table 1:
TABLE 1
Content (wt%)
Carbon (C) 0.20
Boron 0.0010
Silicon ≤0.10
Manganese oxide 0.89
Sulfur ≤0.025
Phosphorus (P) ≤0.025
Through metallographic microscopic examination, the grain size of the low-carbon alloy steel wire rod is 9-10 grades, nonmetallic inclusions are less than or equal to 1 grade, widmannstatten structures are not contained, and the ovality of the low-carbon alloy steel wire rod is less than or equal to 0.20 mm.
S12, sequentially carrying out acid washing and phosphating on the low-carbon alloy steel wire rod, and then carrying out first drawing treatment to obtain a first drawing product;
during acid washing, a 15% hydrochloric acid aqueous solution is adopted for acid washing for 20 min.
During phosphorization, sodium nitrite is used as an accelerating agent;
the first drawing treatment adopts a wire drawing machine, the total compression ratio is more than or equal to 50 percent, and the partial compression ratio is less than or equal to 15 percent.
S13, performing spheroidizing annealing treatment on the first drawing product to obtain a spheroidizing annealing product; the spheroidizing annealing treatment comprises the following steps: under the protective atmosphere, heating the first drawing product to 720 ℃, and preserving heat for 6 hours; then cooling to 550 ℃ at the speed of 20 ℃/h, then continuously cooling to 400 ℃ at the speed of 80 ℃/h, and then naturally cooling to the normal temperature outside the furnace; when the temperature is above 550 ℃, the protective atmosphere is methanol cracking gas, and when the temperature in the furnace is less than 550 ℃, the protective atmosphere is nitrogen;
wherein, the flow rate of the nitrogen is 6L/min, and the flow rate of the methanol cracking gas is 4L/min.
S14, sequentially carrying out acid washing and phosphorization on the spheroidized annealing product, and then carrying out second drawing treatment to obtain the spheroidized annealing product;
during acid washing, a hydrochloric acid aqueous solution with the mass concentration of 10% is adopted for acid washing for 15 min.
During phosphorization, sodium nitrite is used as an accelerating agent;
the second drawing process employs a wire-drawing die.
The automotive fastener wire prepared in this example was tested and the test results are shown in table 2:
TABLE 2
Grade of spheroidisation Grade not less than 5
Grain size Grade not less than 11
Depth of decarburized layer Less than or equal to 1 percent of the diameter of the automobile fastener wire
Thickness of phosphating film 7μm
Cold heading deformation multiple 4
Product grade Grade not less than 8.8
Hardness of product (HV) 220-320
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (7)

1. A preparation method of an automobile fastener wire is characterized by comprising the following steps:
providing a low carbon alloy steel wire having a carbon content of 0.19 wt% to 0.21 wt%, a boron content of 0.0005 wt% to 0.0030 wt%, a sulfur content of 0.025 wt% or less, and a phosphorus content of 0.025 wt% or less;
sequentially carrying out acid pickling and phosphating on the low-carbon alloy steel wire rod, and then carrying out first drawing treatment to obtain a first drawing product;
carrying out spheroidizing annealing treatment on the first drawing product to obtain a spheroidizing annealing product; the spheroidizing annealing treatment comprises the following steps: under the protective atmosphere, heating the first drawing product to 710-730 ℃, and preserving heat for 5-8 hours; then cooling to 540-560 ℃ at a speed of 15-25 ℃/h, then continuously cooling to 390-410 ℃ at a speed of 75-85 ℃/h, and then naturally cooling to normal temperature;
sequentially carrying out acid washing and phosphorization on the spheroidizing annealing product, and then carrying out second drawing treatment to obtain the spheroidizing annealing product;
wherein, sodium nitrite is adopted as an accelerating agent in the phosphorization.
2. The method according to claim 1, wherein the grain size of the low-carbon alloy steel wire rod is 9-10 grades, the non-metallic inclusions are less than or equal to 1 grade, and the low-carbon alloy steel wire rod does not contain Widmannstatten structures.
3. The method of claim 1, wherein the ovality of the low carbon alloy steel wire rod is 0.20mm or less.
4. The preparation method according to claim 1, wherein the temperature of the phosphating is 70-80 ℃ and the time is 8-10 minutes.
5. The method according to claim 1, wherein the total acidity of the phosphating is 20 to 30.
6. The production method according to any one of claims 1 to 5, wherein the acid washing is performed with an aqueous hydrochloric acid solution having a mass concentration of 10% to 15%.
7. The method according to any one of claims 1 to 5, wherein the acid washing time is 15 to 20 min.
CN201811634655.9A 2018-12-29 2018-12-29 Preparation method of automobile fastener wire Pending CN111375649A (en)

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