New energy automobile generator shaft wire rod processing technology

Abstract

The invention relates to the technical field of automobile part production, and discloses a new energy automobile generator shaft wire rod processing technology, which comprises the following steps: 1, raw material screening: selecting a master batch specification according to a product specification with an actual drawing area reduction rate of 35-40%; 2, acid pickling, water washing and lime treatment; thirdly, rough drawing is conducted; step 4, spheroidizing annealing; 5, acid pickling, water washing and phosphorus saponification treatment; and 6, finish drawing is carried out, and the bright fine line is obtained. According to the scheme, the tensile strength of the wire rod before cold heading can be improved to 680-720 MPa by combining and optimizing the processes of acid pickling, rough drawing, annealing and finish drawing, so that the subsequent heat treatment process of the wire rod is changed from full-size hardening and tempering to high-frequency treatment only on the tooth part, the heat treatment cost is greatly reduced, the product competitiveness of downstream customers is improved, and the product quality is improved. Meanwhile, compared with the traditional annealing process, the annealing process of the product is shorter in time, so that the restructuring cost of the fine yarn is greatly reduced, and the production benefit is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of automotive parts production, and particularly relates to a processing technology for wire materials used for the shaft of a new energy vehicle generator. Background Art

[0002] The shaft of a new energy vehicle generator is a core transmission component of the drive motor system of a new energy vehicle. Its function is to transmit the rotational power of the motor rotor to the transmission mechanism, and at the same time, it needs to withstand high-frequency alternating loads, high-speed torques, and dynamic stresses under complex working conditions. With the rapid development of new energy vehicles towards high power density, lightweight, and long endurance, this component poses higher requirements for material properties and processing technologies: a hollow or special-shaped cross-section design is adopted to reduce weight, and it is necessary to ensure that the shaft body still has high load-bearing capacity in the thinned state; the hobbing part needs to mesh precisely with the gear, and it is required that the local area has ultra-high tensile strength (≥680 MPa) and fatigue resistance.

[0003] However, the traditional production process for the existing new energy vehicle generator shafts is as follows: raw materials - pickling, water washing, lime - rough drawing - spheroidizing annealing - pickling, water washing, phosphating - finish drawing - cold heading - machining - hobbing - quenching and tempering - finish grinding. On the one hand, the tensile strength of the current products obtained after finish drawing is generally lower than 600 MPa, and it is impossible to meet the local high-strength requirements directly after cold heading, so it is forced to rely on post-treatment, increasing the processes and costs. On the other hand, the existing process improves the strength through "cold heading forming → overall quenching and tempering (quenching + high-temperature tempering)", but there are the following problems: (1) High cost: The energy consumption of the quenching and tempering process accounts for 35% - 40% of the manufacturing cost, and large-scale heat treatment equipment needs to be equipped; (2) Environmental protection pressure: The volatilization of quenching media (such as oil, polymers) and waste heat emissions are difficult to meet the requirements of carbon neutrality; (3) Performance waste: Only the hobbing part requires high strength, and overall quenching and tempering causes excessive redundancy of material properties. Therefore, how to directly increase the strength of the wire material to 680 - 720 MPa through the process before cold heading without relying on quenching and tempering treatment, while maintaining high plasticity and tissue uniformity has become the core contradiction in the current process improvement.

[0004] Specifically, the prior art CN115161545A discloses a high-plasticity and low-strength medium-carbon cold-heading steel fine wire and its production method. The production method includes the following steps: S1, hot-rolling wire rods; S2, pickling and phosphating; S3, rough drawing. During the rough drawing process, the reduction rate of cross-sectional area in rough drawing is controlled at 30-40%; S3, spheroidizing annealing. The spheroidizing annealing process adopts isothermal spheroidizing annealing: first heating to 600-650°C and holding for 1-1.5 h, then heating to 740-750°C at a rate not higher than 100°C / h and holding for 5-7 h, then cooling to 690-710°C at a rate not higher than 25°C / h and holding for 4-6 h, and finally cooling to below 550°C at a rate not higher than 25°C / h and air-cooling; S4, pickling and phosphating; S5, finish drawing. During the finish drawing process, the reduction rate of cross-sectional area in finish drawing is controlled at 3-6%. A medium-carbon cold-heading steel fine wire with low strength and high plasticity is obtained. The tensile strength of the medium-carbon cold-heading steel fine wire is ≤530 MPa, the reduction of area is ≥70%, the hardness is ≤85 HRB, and the spheroidizing grade is ≥5 grades, meeting the dual requirements of customers for quality and cost. However, the prior art still has the following technical problems:

[0005] (1) The prior art sacrifices strength for plasticity, which runs counter to the target requirements; the cold-heading steel fine wire produced by it has a low tensile strength (tensile strength ≤530 MPa) and cannot meet the performance requirements of the tensile strength of 680-720 MPa for the generator shaft of new energy vehicles; moreover, the wire produced by the prior art still needs to rely on quenching and tempering to supplement strength after cold heading, increasing the cost and reducing the cost performance of the overall process.

[0006] (2) If the prior art is used to produce the generator shaft of new energy vehicles, starting from the preparation of steelmaking raw materials, not only the existing raw materials of the enterprise cannot be used, but also additional steelmaking-related equipment needs to be equipped, further increasing the production cost and reducing the market competitiveness;

[0007] (3) If S2-S5 in the existing fine wire production method is used to process the existing raw materials, due to the mismatch between the materials and the process, a cold-heading steel fine wire that cannot meet the performance requirements of the tensile strength of 680-720 MPa for the generator shaft of new energy vehicles cannot be obtained.

[0008] In view of this, researching and developing a wire processing process for the generator shaft of new energy vehicles with low cost can not only effectively make up for the deficiencies of the prior art, but also fully reduce the production cost and enhance the market competitiveness of the product on the premise of meeting the high-performance requirements of the wire for the generator shaft of new energy vehicles. Summary of the Invention

[0009] The present invention aims to provide a wire processing process for the generator shaft of new energy vehicles to solve the technical problem that the tensile performance of the wire produced by the prior art cannot meet the requirements of the generator shaft of new energy vehicles, and additional quenching and tempering treatment is required after cold heading, increasing the cost.

[0010] To achieve the above object, the present invention adopts the following technical solution: a wire processing process for a generator shaft of a new energy vehicle, comprising the following steps:

[0011] Step 1: Raw material selection: According to product specifications, select the masterbatch specifications with a drawing reduction rate of 35-40%;

[0012] Step 2, pickling, water washing, lime treatment: the masterbatch is coiled and pickled, water washed and limed;

[0013] Step 3, rough drawing: rough drawing the wire rod obtained in step 2;

[0014] Step 4: Spheroidizing annealing: annealing the rough drawn wire, the tensile strength of the wire after annealing is 530-580 MPa;

[0015] Step 5, pickling, water washing, and phosphorus saponification treatment: the annealed wire is sequentially pickled, water washed, and phosphorus saponified;

[0016] Step 6, fine drawing: fine drawing is performed on the wire obtained in step 5 to obtain a light fine wire, wherein the tensile strength of the light fine wire is 680-720 MPa.

[0017] The principles and advantages of this solution are:

[0018] 1. Compared with the existing technology, the tensile properties of the wire produced cannot meet the requirements of the generator shaft of new energy vehicles and need to be tempered as a whole after cold heading, which increases the cost. This solution combines and optimizes the pickling, rough drawing, annealing and fine drawing processes to increase the tensile strength of the wire before cold heading to 680-720MPa, so that the subsequent heat treatment process is changed from full-size tempering to high-frequency treatment only on the teeth, which greatly reduces the heat treatment cost and improves the product competitiveness of downstream customers. At the same time, because the annealing process of this product is shorter than the traditional annealing process, the cost of remaking the light wire and fine wire is greatly reduced, thereby improving production efficiency.

[0019] 2. Because the cold extrusion effect during cold heading will increase the instantaneous hardness and strength of the wire, when the tensile strength of the light wire is too high, it will lead to excessive resistance in subsequent cold heading and significantly reduce the service life of the mold. This solution effectively controls the tensile strength of the light wire obtained by the reformation between 680 and 720 MPa by optimizing the process at each stage, which ensures the smoothness of the cold heading process and meets the tensile strength performance requirements after subsequent heat treatment.

[0020] 3. By limiting the tensile strength of the wire after annealing in this solution, the deformation resistance during fine drawing is effectively reduced, thereby reducing the drawing force to be applied, lowering energy consumption, and making it easier to meet the product requirements of obtaining a high tensile strength after fine drawing. Moreover, reducing the deformation resistance during fine drawing can effectively increase the area reduction rate during fine drawing while avoiding the risk of wire breakage. Furthermore, the low tensile strength after annealing facilitates the full recrystallization of the wire. The fully recrystallized fine-grained structure provides a basis for uniform deformation, making the gradient distribution of dislocation density after fine drawing smoother, narrowing the strength fluctuation range of the final product, and improving the uniformity of product performance. Through long-term experiments, the applicant found that if the tensile strength of the wire obtained after rough drawing and annealing is too high (such as reaching 600 MPa or above), the subsequent fine drawing will be more difficult due to its too high tensile strength, and more energy consumption will be required to achieve the same area reduction rate during fine drawing. This not only increases production costs but also easily causes wire breakage, reducing the product yield. Moreover, too high strength after annealing indicates incomplete recrystallization and a relatively high residual dislocation density. The increment of new dislocations that can be introduced during fine drawing is limited, resulting in a final strength lower than 650 MPa, making it difficult to meet the product tensile strength requirement of 680 - 720 MPa.

[0021] Preferably, as an improvement, in step three, the area reduction rate during rough drawing is 18 - 20%; the drum diameter of the wire drawing machine used for rough drawing is 1000 - 1200 mm.

[0022] Technical effect: With the above settings in this solution, using a lower area reduction rate in the preliminary drawing can retain the initial plasticity of the material and avoid premature embrittlement, thereby reducing the product yield. Specifically, by limiting the low deformation amount (18 - 20%) in the rough drawing stage in this solution, the degree of work hardening can be reduced, and the original ductility of the material can be retained (such as the initial elongation rate of 15% → still remaining above 12% after processing), providing a plastic reserve for the large deformation during subsequent fine drawing. Moreover, the slightly lower area reduction rate in the rough drawing stage can make the wire have a lower dislocation density. On the one hand, it facilitates the full recrystallization during the annealing process and improves the grain size uniformity; on the other hand, it can effectively shorten the annealing time and reduce energy consumption. Furthermore, the low area reduction rate in rough drawing can effectively reduce the die friction heat, inhibit the formation of oxide scale, and reduce the material loss rate.

[0023] Preferably, as an improvement, in step six, the area reduction rate during fine drawing is 22 - 24%; the drum diameter of the wire drawing machine used for fine drawing is 1200 - 1400 mm.

[0024] Technical effect: With the above settings in this solution, setting a higher area reduction rate during fine drawing can apply concentrated pressure through a large deformation amount to generate a high density of dislocation tangles, directly driving a jump in the tensile strength; combined with the gradient deformation strategy, the final tensile strength can exceed 690 MPa while maintaining an elongation rate ≥ 12%, thereby improving the product performance. In addition, using high-precision dies in the fine drawing stage in combination with a large area reduction rate can simultaneously achieve high strength and high surface finish, improving the overall performance of the product.

[0025] Preferably, as an improvement, in step four, the highest temperature of the annealing is 665 - 680 °C, and the total annealing time is 20 - 24 h.

[0026] Technical effect: With the above settings in this solution, it is convenient to effectively reduce the tensile strength of the wire after annealing, and it is convenient for the wire to significantly improve the tensile strength of the product after precision drawing, breaking through 680 MPa, fully meeting the product requirements.

[0027] Preferably, as an improvement, the temperature control method during annealing is as follows: Heat up with the furnace to the first temperature of 550 - 580 °C and isotherm for 1.5 - 2 h; then heat up with the furnace to the second temperature of 630 - 650 °C and isotherm for 0.8 - 1 h, and then heat up to the third temperature of 665 - 680 °C in 0.8 - 1 h and isotherm for 5 - 6 h; then cool down to the fourth temperature of 630 - 650 °C in 1.5 - 2 h and then cool down with the furnace to 570 - 580 °C and take out of the furnace.

[0028] Technical effect: With the above settings in this solution, it is convenient to reduce the material hardness through globular pearlite structure, improve plasticity, and reduce the cracking risk during cold drawing; it can also inhibit the precipitation of carbide network, homogenize the structure, and effectively refine the grains; during the process, it can effectively eliminate the processing stress, reduce the subsequent heat treatment deformation, and stabilize the dimensions.

[0029] Specifically, at the first temperature gradient, the material starts to austenitize partially at the first temperature, reducing the subsequent heating thermal stress, and the isothermal treatment dissolves part of the carbides; then at the second temperature, the pearlite is transformed into austenite, and the isothermal treatment promotes the formation of the spheroidization core of carbides; then at the third temperature, uniform austenite is formed, and the isothermal treatment dissolves the carbides fully. During this process, if the third temperature is too high, it will cause the austenite grains to be coarse, resulting in the coarsening of the final carbide particles; and if the isothermal time at the third temperature is too short, it will lead to insufficient dissolution of the carbides, and local stress concentration is likely to occur during cold drawing. During the subsequent cooling to the fourth temperature, by controlling the cooling rate, the precipitation of globular carbides is effectively promoted, and the isothermal treatment makes the pearlite lamellar spacing more refined. If the cooling rate is too fast in this stage, lamellar pearlite will be formed, causing the work hardening index of the material to increase sharply by 50% during cold drawing, reducing its processing plasticity; and if the isothermal time at the fourth temperature is too long, the strength and toughness matching of the material will be reduced due to excessive aggregation of carbides.

[0030] Preferably, as an improvement, the control method of the atmosphere during annealing is as follows: Open a small flow of nitrogen of 2 m 3 / h throughout the annealing stage, and simultaneously open a large flow of nitrogen of 10 m 3 / h. After the furnace temperature reaches the first temperature, start methanol at 25 ml / min and shut off the large nitrogen flow. When half of the holding time at the third temperature has elapsed, the methanol flow rate changes to 20 ml / min, and methanol is shut off after the holding at the third temperature ends. When the temperature drops to the fourth temperature, start the large nitrogen flow at 10 m 3 / h until the furnace is out of the oven, and the small nitrogen flow remains unchanged.

[0031] Technical effect: With the above settings in this solution, it is convenient to achieve the comprehensive goals of anti-oxidation, carbon potential control, and microstructure refinement. Specifically, the small nitrogen flow throughout the process maintains a basic inert environment to prevent trace oxygen from invading and causing surface oxidation. Starting the large nitrogen flow at a low temperature can quickly replace the residual air in the furnace to ensure that the oxygen content is <50 ppm before the high-temperature stage, avoiding the oxidation of ferrite to generate Fe 3 O 4 . And switching to methanol at 25 ml / min (cracking into CO + H 2 ) at high temperature is convenient to maintain a reducing atmosphere with CO / H2 at high temperature and inhibit oxidation; at the same time, CO provides a carbon potential (C% ≈ 0.3 - 0.4%), preventing surface decarburization; as half of the holding time at the highest temperature has elapsed, the carbon potential is reduced to 0.2% - 0.25% to avoid carbide coarsening at grain boundaries due to overcarburization and ensure the spheroidization uniformity. Finally, restarting the large nitrogen flow after the temperature drops to a lower temperature is convenient to inhibit the carbon black deposition caused by the residual CO during the cooling process and prevent secondary oxidation caused by the infiltration of oxygen. The applicant found through long-term experiments that if there is no continuous small nitrogen flow protection, the local oxygen concentration in the furnace will increase, and Fe and O 2 easily react to generate FeO / Fe 3 O 4 , and the surface oxide scale thickens; decarburization will also intensify, resulting in insufficient strength at the hobbing part after cold heading. And if the methanol flow rate is not reduced when half of the holding time has elapsed, due to the high carbon potential maintained, overcarburization will cause carbides to accumulate at grain boundaries, forming chain-like carbides after spheroidizing annealing; the plasticity of the material will also decrease, making cold heading prone to cracking. And if methanol is directly shut off when half of the holding time has elapsed, due to the sudden drop of the carbon potential to 0% (only relying on the small nitrogen flow), the surface decarburization will accelerate, resulting in a tensile strength <650 MPa; and the H 2 content in the furnace is insufficient, and the residual oxygen causes local oxidation, increasing the surface roughness Ra to more than 1.0 μm. And if there is no large nitrogen flow, the oxygen removal in the heating stage is not complete, resulting in severe initial oxidation, forming coarse oxide particles on the surface, and causing microcracks during drawing; local decarburization will also cause strength fluctuations (±50 MPa). And if there is no methanol protection, there is no CO / H 2 reducing atmosphere at high temperature, and the carbon potential approaches 0, which will lead to significant surface decarburization and a reduction in tensile strength to below 600 MPa; in addition, grain boundary oxidation (Fe-Cr oxides at grain boundaries) causes brittle fracture.

[0032] Preferably, as an improvement, in Step 2 and Step 5, the pickling treatment is as follows: After soaking the material in warm water at 50 - 65°C, first pickle it in pickling solution with a concentration of 5 - 10% for 10 - 20 minutes, then pickle it in pickling solution with a temperature of 35 - 40°C and a concentration of 10 - 15% for 5 - 15 minutes, and finally pickle it in pickling solution with a temperature of 35 - 40°C and a concentration of 15 - 20% for 3 - 10 minutes.

[0033] Technical effect: With the above settings in this solution, soaking the material in warm water at 50 - 65°C before pickling facilitates more thorough removal of the oxide scale on the surface of the wire rod, and at the same time can effectively remove dirt such as surface oxide shells and ash, improving the cleanliness of the wire rod. The staged gradient pickling is adopted to facilitate efficient rust removal and improve the surface cleanliness of the material. Specifically, through the concentration gradient design (5 - 10% → 10 - 15% → 15 - 20%), a three - stage process of "pre - reaction - main reaction - fine treatment" is formed, ensuring efficient pickling while effectively reducing the amount of hydrogen penetration and reducing the risk of hydrogen embrittlement. Moreover, in the actual process of multi - gradient pickling, it can effectively avoid over - corrosion caused by a single high - concentration pickling solution and also avoid incomplete rust removal caused by a single low - concentration pickling solution.

[0034] Preferably, as an improvement, in Step 2 and Step 5, the water washing treatment is carried out in four - stage water washing in a soup washing pool with pH 5 - 7, a soup washing pool with pH 5.5 - 7, a soup washing pool with pH 5 - 7, and a soup washing pool with pH 5.5 - 7 in sequence.

[0035] Technical effect: With the above settings in this solution, it is convenient to remove the influence of residual pickling solution, improve the surface cleanliness, and can also prevent the pickling solution from entering the subsequent phosphating tank and polluting the phosphating solution. And through pH gradient control, different pH values in the four - stage water washing pool form a dynamic neutralization gradient, avoiding precipitation (such as CaCO 3 precipitation) caused by local over - neutralization. Moreover, compared with single - stage water washing, four - stage counter - current rinsing can significantly reduce the residual acid concentration. The applicant found through long - term experiments that if the number of water washing times is insufficient, hydrogen embrittlement will be caused during cold processing of the material due to the residual pickling solution, reducing the material strength; and the residual pickling solution will also increase the porosity of the phosphating film, thereby reducing its corrosion resistance. If the pH is too high, white flocculent precipitates (Ca(OH) 2 ) are likely to form on the surface of the workpiece, making the phosphating film locally thinner, resulting in "crater" defects after coating baking and a decrease in corrosion resistance. If the pH is too low, the material will rust back (Fe 2 O 3 ·nH 2 O) after water washing, reducing the bonding force between the phosphating film and the substrate, and then reducing the film adhesion during saponification treatment and causing cold - working lubrication failure.

[0036] Preferably, as an improvement, in step two, the lime treatment is carried out in a lime pool with a mass fraction of 30-40% for 2-3 minutes.

[0037] Technical effect: With the above settings in this solution, it is convenient to neutralize the acid liquid remaining on the surface of the material after water washing, avoiding the continuous reaction of the remaining acid liquid with the steel, which affects the quality and performance of the steel. In addition, the lime coating can also form a dense alkaline film on the surface of the wire rod, isolating air and moisture, and preventing the wire rod from rusting during transportation or storage. Furthermore, during the drawing process, the lime layer can also reduce the friction coefficient between the die and the wire rod, reduce surface scratches and heat accumulation, and prevent drawing cracking.

[0038] Preferably, as an improvement, in step five, the phosphating and saponifying treatment includes oxalic acid treatment, phosphating treatment, and saponifying treatment in sequence; the oxalic acid treatment is carried out at an oxalic acid concentration of 10-15 Pt for 3-5 minutes; the phosphating treatment is carried out in a phosphating pool at a temperature of 74-78 °C, free acid of 7-9 Pt, total acidity of 49-52 Pt, acid ratio of 6-6.5, acceleration of 1-3 Pt, and phosphate root ratio of 0.4-0.5 for 4-6 minutes; the saponifying treatment is carried out in a saponifying solution at a temperature of 80-85 °C, pH of 8-9, oil content of 0.8-1.3 Pt, and sugar content of 1-2 Pt for 5-8 minutes.

[0039] Technical effect: With the above settings in this solution, it is convenient to form protective films such as phosphating films and saponifying films on the surface of the wire rod, reduce the friction coefficient during cold processing, and reduce wear; the saponifying layer can seal the pores of the phosphating film and improve the corrosion resistance. Among them, oxalic acid forms stable complexes with Fe2+, Fe3+, Cu2+ etc., removes the metal salts remaining after pickling, and deeply purifies the surface; it can also effectively dissolve the remaining Cr 2 O 3 , improves the surface activity; it can also cause selective corrosion on the metal surface, provides more active sites for the phosphating reaction through the micro-pit structure, and improves the subsequent phosphating film effect. It is convenient to form a saponifying layer on the surface of the phosphating film.

[0040] The applicant has found through long-term experiments that if oxalic acid treatment is not adopted, the problem of mottling of the phosphating film caused by residual metal ion pollution will also lead to a decrease in the nucleation density of the phosphating film due to insufficient surface activity, resulting in poor film layer continuity and affecting the material properties. If the phosphating temperature is too high, the film layer will be too thick, leading to an increase in brittleness and easy cracking after painting; it will also cause the evaporation of the bath solution to intensify and the free acid to rise faster, affecting the phosphating effect. If the phosphating temperature is too low, the film formation rate will be significantly reduced, the film weight will be reduced, and the corrosion resistance of the film will be insufficient, and "yellow rust" (FeOOH) is likely to appear, especially causing batch defects in continuous production lines. If the free acid is too high, "over-corrosion" will occur due to excessive dissolution of the substrate, resulting in a decrease in the adhesion of the film layer; it will also cause the acid ratio to be <6, resulting in coarse crystallization, easy adsorption of oil stains, and reduction of the phosphating film performance effect. If the free acid is too low, the film layer will be incomplete due to the difficulty in starting the phosphating reaction, and the bath solution stability will be reduced, and zinc phosphate precipitation is likely to occur (the slag amount increases by 2-3 times). If the total acidity is too high, the film layer will be too dense due to the acid ratio >6.5, resulting in a decrease in adhesion, and the phosphating slag amount will also increase by 15%-20%, blocking the spray system. If the acceleration degree is too low, the phosphating film may be too thin and the corrosion resistance may be insufficient; if the acceleration degree is too high, the film layer may be rough and the phosphating slag may increase. In the saponification stage, if the pH is too high, the corrosiveness of the solution will increase, damaging the bottom layer of the phosphating film and causing the coating to blister; if the pH is too low, the saponification reaction will be incomplete, resulting in a decrease in the hot water resistance of the film layer. If the oil content is too high, the viscosity of the solution will increase, and oil spots will remain on the surface of the workpiece, affecting the appearance of the coating (such as gloss). If the oil content is too low, the film layer will be insufficient in thickness, the friction will increase during cold processing, and the die life will be shortened. If the sugar content is too high, microorganisms are likely to grow in the solution, leading to spoilage and a soaring COD value. If the sugar content is too low, the solution stability will decrease, stratification or precipitation will occur, affecting the film layer uniformity. If the treatment time is too long, the film layer will be too thick, resulting in an increase in brittleness, an increase in the consumption of the solution, and an increase in production costs; and long-term treatment at high temperatures may cause recrystallization of the film layer. If the treatment time is too short, the film layer will be incomplete, and dry friction will occur locally during cold processing, generating scratches. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 FIG. is a numerical control chart adopted in the annealing stage of the wire processing process for the generator shaft of a new energy vehicle in Embodiment 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0042] The present invention will be further described in detail below with reference to the embodiments, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the technical means used in the following embodiments and experimental examples are conventional means well known to those skilled in the art, and the materials, reagents, etc. used can be obtained from commercial channels.

[0043] Example 1

[0044] This solution provides a processing technology for the wire material used in the generator shaft of new energy vehicles, including the following steps:

[0045] Step 1. Raw material screening: According to the product specifications, select the mother material specifications with an actual drawing area reduction rate of 35 - 40%; specifically, for the product with a specific production specification of Φ18.87mm and a tensile strength requirement of 680 - 720MPa in this example, the coil with a material of SWRCH45K, a specification of Φ24mm, and a tensile strength of 450 - 570MPa can be selected.

[0046] Step 2. Pickling, water washing, and lime treatment: Perform pickling treatment, water washing treatment, and lime treatment on the mother material coil in sequence; specifically, the pickling treatment is as follows: After soaking the material in warm water at 50 - 65°C, first pickle it in acid solution with a concentration of 5 - 10% for 10 - 20min, then pickle it in acid solution with a temperature of 35 - 40°C and a concentration of 10 - 15% for 5 - 15min, and finally pickle it in acid solution with a temperature of 35 - 40°C and a concentration of 15 - 20% for 3 - 10min.

[0047] The water washing treatment is carried out in four - stage water washing in a hot water washing pool with pH5 - 7, a hot water washing pool with pH5.5 - 7, a hot water washing pool with pH5 - 7, and a hot water washing pool with pH5.5 - 7 in sequence.

[0048] The lime treatment is carried out in a lime pool with a mass fraction of 30 - 40% for 2 - 3min.

[0049] Step 3. Rough drawing: Use a wire drawing machine with a drum diameter of 1000mm (as a reference, the rough drawing equipment is the Zheng Yi wire drawing machine from Taiwan, China) to perform rough drawing on the wire rod obtained in Step 2, and the rough drawing area reduction rate is 19.75%.

[0050] Step 4. Spheroidizing annealing: Anneal the wire rod after rough drawing, and the tensile strength of the wire rod after annealing is 555MPa; the highest annealing temperature is 680°C, and the total annealing time is 20 - 24h; specifically, Figure 1 as shown, the temperature control method during annealing is as follows: Heat up in the furnace to the first temperature of 580°C and isotherm for 2h; heat up in the furnace to the second temperature of 650°C and isotherm for 1h, then raise the temperature to the third temperature of 680°C in 1h and isotherm for 6h; then cool down to the fourth temperature of 650°C in 2h and then cool down to 580°C with the furnace and take out of the furnace (it should be noted that Figure 1 all the stages showing "1min" are heating up or cooling down with the furnace, not limited to 1min). The atmosphere control method during annealing is as follows: Open the small - flow nitrogen at 2m 3 / h throughout the annealing stage, and open the large - flow nitrogen at 10m 3 / h. After the furnace temperature reaches the first temperature of 580°C, start methanol at 25 ml / min and close the large nitrogen flow; when half of the holding time at the third temperature has passed (i.e., after holding at 680°C for 3 h), the methanol flow rate becomes 20 ml / min, and after the holding at the third temperature ends (i.e., after holding at 680°C for another 3 h), turn off the methanol; when the temperature drops to the fourth temperature of 650°C, start the large nitrogen flow at 10 m 3 / h until the furnace is out. The small nitrogen flow remains open and unchanged throughout the annealing process.

[0051] Step Five: Pickling, Water Washing, and Phosphating Treatment: The wire rods obtained from annealing are successively subjected to pickling treatment, water washing treatment, and phosphating treatment; specifically, the pickling treatment is as follows: After soaking the material in warm water at 50 - 65°C, first pickle in acid solution with a concentration of 5 - 10% for 10 - 20 min, then pickle in acid solution with a temperature of 35 - 40°C and a concentration of 10 - 15% for 5 - 15 min, and finally pickle in acid solution with a temperature of 35 - 40°C and a concentration of 15 - 20% for 3 - 10 min.

[0052] The water washing treatment is carried out in four - stage water washing in a soup - washing pool with pH 5 - 7, a soup - washing pool with pH 5.5 - 7, a soup - washing pool with pH 5 - 7, and a soup - washing pool with pH 5.5 - 7 in sequence.

[0053] The content of the phosphating treatment includes oxalic acid treatment, phosphating treatment, and saponification treatment carried out in sequence; the oxalic acid treatment is carried out for 3 - 5 min under the condition that the oxalic acid concentration is 10 - 15 Pt; the phosphating treatment is carried out in a phosphating bath with a temperature of 74 - 78°C, free acid of 7 - 9 Pt, total acidity of 49 - 52 Pt, acid ratio of 6 - 6.5, promotion degree of 1 - 3 Pt, and phosphate root ratio of 0.4 - 0.5 for 4 - 6 min; the saponification treatment is carried out in a saponification solution with a temperature of 80 - 85°C, pH 8 - 9, oil content of 0.8 - 1.3 Pt, and sugar content of 1 - 2 Pt for 5 - 8 min.

[0054] Step Six: Fine Drawing: Use a wire drawing machine with a drum diameter of 1200 mm (as a reference, the rough drawing equipment is Anhui Litian wire drawing machine) to carry out fine drawing on the wire rods obtained in Step Five. The designed reduction ratio of the fine drawing is 22.97%, and the obtained bright wire fine line has a tensile strength of 698 MPa, a hardness of 95 HRB, an elongation of 12 - 14%, a spheroidization grade of 2.5 - 4 levels, and decarburization ≤ 0.03 mm, fully meeting the performance requirements of the wire rods for the generator shaft of new energy vehicles.

[0055] For the differences in the steps and parameters of the processing technology of the wire rods for the generator shaft of new energy vehicles in Examples 1 - 3 and Comparative Example 1, see Table 1 in detail.

[0056] Table 1 Differences in the steps and parameters of the processing technology of the wire rods for the generator shaft of new energy vehicles in Examples 1 - 3 and Comparative Example 1

[0057]

[0058] Experimental Example 1: Quality Inspection of Finished Products

[0059] The performance of the wire rods produced by the processes in Examples 1 to 3 and Comparative Example 1 was tested, and the results are shown in Table 2.

[0060] Table 2 Performance of Wire Rods Produced by the Processes in Examples 1 to 3 and Comparative Example 1

[0061]

[0062] Experimental data show that by combining and defining the reduction ratio of rough drawing, the maximum annealing temperature, and the reduction ratio of finish drawing, the tensile strength of the wire rods of the product line is effectively increased to 680 - 720 MPa, fully meeting the performance requirements of the wire rods for the generator shafts of new energy vehicles, enabling the subsequent heat treatment process to be changed from full-size quenching and tempering to only high-frequency treatment at the tooth part, greatly reducing the heat treatment cost, improving the product competitiveness of downstream customers. At the same time, because the annealing process of this product is shorter than the traditional annealing process, the cost of reforming bright wire into precision wire is greatly reduced.

[0063] The above are only the embodiments of the present invention. Specific technical solutions and / or common knowledge such as characteristics well known in the art are not described in detail herein. It should be noted that for those skilled in the art, without departing from the technical solution of the present invention, several deformations and improvements can still be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicality of the patent. The protection scope required by this application should be based on the content of its claims, and the specific implementation manners described in the specification can be used to interpret the content of the claims.

Claims

1. Wire processing technology for generator shaft of new energy vehicle, characterized by: The steps include: Step 1: Raw material selection: According to product specifications, select the masterbatch specifications with an actual drawing reduction rate of 35-40%; Step 2, pickling, water washing, lime treatment: the masterbatch is coiled and pickled, water washed and limed; Step 3, rough drawing: rough drawing the wire rod obtained in step 2; Step 4: Spheroidizing annealing: annealing the rough drawn wire, the tensile strength of the wire after annealing is 530-580 MPa; Step 5, pickling, water washing, and phosphorus saponification treatment: the annealed wire is sequentially pickled, water washed, and phosphorus saponified; Step 6, fine drawing: fine drawing is performed on the wire obtained in step 5 to obtain a light fine wire, wherein the tensile strength of the light fine wire is 680-720 MPa.

2. The wire material processing process for the generator shaft of a new energy vehicle according to claim 1 is characterized in that: In step three, the rough drawing reduction ratio is 18-20%; the drum diameter of the wire drawing machine used for the rough drawing is 1000-1200 mm.

3. The wire material processing process for the generator shaft of a new energy vehicle according to claim 1 is characterized in that: In step six, the surface reduction ratio of fine drawing is 22-24%; the drum diameter of the wire drawing machine used for fine drawing is 1200-1400 mm.

4. The wire material processing process for the generator shaft of a new energy vehicle according to claim 1 is characterized in that: In step 4, the maximum annealing temperature is 665-680° C., and the total annealing time is 20-24 hours.

5. The wire material processing process for the generator shaft of a new energy vehicle according to claim 4 is characterized in that: The temperature control method during annealing is as follows: heating to a first temperature of 565-580°C and isothermal for 1.5-2h; heating to a second temperature of 640-650°C and isothermal for 0.8-1h; then heating to a third temperature of 665-680°C and isothermal for 5-6h after 0.8-1h; then cooling to a fourth temperature of 640-650°C after 1.5-2h, and then cooling to 570-580°C before being taken out of the furnace.

6. The wire material processing process for the generator shaft of a new energy vehicle according to claim 5 is characterized in that: The method for controlling the atmosphere during annealing is as follows: a small flow rate of 2m nitrogen is opened during the entire annealing stage. 3 / h, before the furnace temperature reaches the first temperature, turn on the nitrogen gas with a large flow rate of 10m 3 / h, when the furnace temperature reaches the first temperature, turn on 25ml / min methanol and turn off the large flow of nitrogen; when the third temperature insulation time is halfway, the methanol flow rate becomes 20ml / min, and the methanol is turned off after the third temperature insulation ends; when the temperature drops to the fourth temperature, turn on the large flow of nitrogen 10m 3 / h until it comes out of the furnace, and the small flow rate of nitrogen remains unchanged.

7. The wire material processing process for the generator shaft of a new energy vehicle according to claim 1 is characterized in that: In step 2 and step 5, the pickling treatment is: after soaking the material in warm water at 50-65°C, first pickle in an acid solution with a concentration of 5-10% for 10-20 minutes, then pickle in an acid solution with a temperature of 35-40°C and a concentration of 10-15% for 5-15 minutes, and finally pickle in an acid solution with a temperature of 35-40°C and a concentration of 15-20% for 3-10 minutes.

8. The wire material processing process for the generator shaft of a new energy vehicle according to claim 1 is characterized in that: In step 2 and step 5, the water washing treatment is carried out in four stages in a water washing pool with a pH value of 5 to 7, a water washing pool with a pH value of 5.5 to 7, a water washing pool with a pH value of 5 to 7 and a water washing pool with a pH value of 5.5 to 7.

9. The wire material processing process for the generator shaft of a new energy vehicle according to claim 8 is characterized in that: In step 2, the lime treatment is carried out in a lime pool with a mass fraction of 30-40% for 2-3 minutes.

10. The wire material processing process for the generator shaft of a new energy vehicle according to claim 9, characterized in that: In step five, the phosphosaponification treatment includes oxalic acid treatment, phosphating treatment and saponification treatment in sequence; the oxalic acid treatment is a treatment for 3 to 5 minutes under the condition of an oxalic acid concentration of 10 to 15Pt; the phosphating treatment is a treatment for 4 to 6 minutes in a phosphating tank with a temperature of 74 to 78°C, a free acid of 7 to 9Pt, a total acidity of 49 to 52Pt, an acid ratio of 6 to 6.5, a promotion degree of 1 to 3Pt, and a phosphate ratio of 0.4 to 0.5; the saponification treatment is a treatment for 5 to 8 minutes in a saponification solution with a temperature of 80 to 85°C, a pH of 8 to 9, a fat content of 0.8 to 1.3Pt, and a sugar content of 1 to 2Pt.

Images