Hot forging forming process for automobile guide arm

Abstract

The invention relates to the technical field of automobile part forging, in particular to a hot forging forming process for an automobile guide arm. The method comprises the four key steps of round steel heating, roll forging blank making, high-energy press forming and trimming correction, one-time forming of a product is achieved, the purposes of improving the product quality, saving the labor cost and improving the production efficiency are achieved, and meanwhile the problems that an existing process depends on material models and occupies a large site are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of automobile parts forging technology, and particularly relates to a hot forging forming process of an automobile guide arm. BACKGROUND

[0002] As a core force transmission and guide element of the automobile chassis suspension system, the automobile guide arm directly affects the stability, safety and comfort of the vehicle driving, and the advancement of the production process is crucial to the product quality and production efficiency. At present, the production process of the automobile guide arm mainly includes traditional welding process and forging process, but both processes have significant technical defects, which are difficult to meet the needs of large-scale and high-quality production of the automobile industry.

[0003] The traditional production process generally adopts the mode of cutting steel plates and pipe materials and then welding forming. This process has multiple inherent defects: first, the material universality is poor, and multiple types and thicknesses of steel materials need to be prepared to adapt to different specifications of guide arms, resulting in high material procurement and inventory costs; second, the production site occupies a large area, and the dispersed processes such as cutting and welding need independent operation space, which has low space utilization; third, it relies on a large number of manual operations, the strength of the welded joint is easily affected by human factors, the product quality consistency is poor, and the organization compactness and mechanical properties of the welded parts are far inferior to those of the forged parts; fourth, the long production cycle and low production efficiency caused by complicated processes cannot meet the large-scale production needs.

[0004] To improve the shortcomings of the welding process, various guide arm forging related technologies have been gradually developed in the industry, but the existing forging process still has many problems to be solved: some technologies focus on the design of universal molds for special-shaped arms, which realize the production of multiple specifications through the adjustment of mold movable blocks, although the mold cost is reduced, but the full-process automatic process parameter optimization is not involved, and it relies on large-scale forging equipment above 4000t, which has high production threshold; for the forging process of transmission steering arms and similar structural parts, there are problems such as low material utilization rate, easy production of displacement and folding defects of forged parts, and poor size precision, which requires a large machining allowance, resulting in material waste and low machining efficiency; although the aluminum alloy control arm forging process meets the lightweight demand, it is limited by the material properties and is prone to penetrating cracks at large corners, and the material utilization rate is only about 50%, at the same time, the forging parameters and process route are difficult to directly adapt to the production of steel guide arms; although some forging production lines introduce automatic equipment, there are problems such as unsmooth process connection, poor temperature uniformity caused by backward heating method, lack of coherent heat treatment links, etc., which cause unstable product quality and prolonged production cycle; another technology improves the toughness of the guide arm by optimizing the composition of the spring steel material, but it does not solve the problems of parameter matching and multi-model adaptability in the forging process, and the control effect on the hardenability of large cross-section products is limited.

[0005] In addition, the existing forging process also has obvious limitations: first, the material adaptation range is narrow, most processes are only optimized for single material such as aluminum alloy, specific spring steel, etc., and it is difficult to meet the forging requirements of common structural steels such as 45 steel, 40Cr, 20CrMnTi, etc.; second, the process parameters lack systematic design, and the matching of key parameters such as heating temperature, roll forging pass, press tonnage is insufficient, which leads to defects such as coarse grain and size out-of-tolerance of the forgings; third, the degree of automation is insufficient, and some processes still rely on manual transfer and operation, which not only has high labor intensity, but also easily affects the product quality stability due to human intervention; fourth, the application range is limited, and the existing technology is mainly designed for small or specific structure guide arms, which is difficult to meet the diversified needs of different vehicle models such as small cars, medium SUVs and commercial vehicles, and lacks a whole-process solution that takes into account quality, efficiency and cost.

[0006] In summary, neither the traditional welding process nor the existing forging technology can effectively solve the comprehensive technical problems of material versatility, production automation, parameter optimization, multi-vehicle model adaptation and product quality stability, and a production method for automobile guide arms with perfect process route, scientific parameter design and high degree of automation is urgently needed to make up for the shortcomings of existing technology. SUMMARY

[0007] In view of the above-mentioned shortcomings of the prior art, a hot forging forming process for automobile guide arms is provided, which realizes one-time forming of the product, achieves the purposes of improving product quality, saving labor cost and improving production efficiency, and solves the problems of dependence on material type and large site occupation of the existing process.

[0008] To solve the above technical problems, the technical solution adopted by the present application is an automatic hot forging forming method for automobile guide arms, comprising the following steps:

[0009] (1) Selecting round steel of 45, 40Cr or 20CrMnTi material as raw material, feeding into a medium frequency furnace for heating, and controlling the heating temperature to be 1100-1150℃;

[0010] (2) Using a roll forging machine with a diameter of 1000mm to roll forge the heated round steel for 1-3 passes to obtain a blank with a preset cross-sectional shape;

[0011] (3) Completing the bending, pre-forging and finish-forging forming processes in turn by an 8000T high-energy press, and the holding time of each process is 2-5s;

[0012] (4) Using a 1600T electric screw press to trim and correct the formed workpiece, and the straightness error of the corrected workpiece is ≤0.3mm / m, to obtain an automobile guide arm finished product.

[0013] In the above-mentioned automated hot forging method, in step (1), the heating rate of the medium frequency furnace is 4-9℃ / s, the holding time of the round steel is 8-18min, and the diameter of the round steel is 60-120mm.

[0014] In the above-mentioned automated hot forging method, in step (2), the roller speed of the roll forging machine is 15-30 r / min, and the roller gap adjustment range is 30-80 mm.

[0015] In the above-mentioned automated hot forging method, in step (3), the press stroke speed of the bending process is 25-35 mm / s, the pre-forging process is 18-22 mm / s, and the final forging process is 12-18 mm / s.

[0016] In the above-mentioned automated hot forging method, in step (4), the pressure of the trimming process is 800-1200T, and the pressure of the correction process is 500-800T.

[0017] In the above-mentioned automated hot forging method, the oxide scale thickness on the surface of the round steel after heating is ≤0.5mm, and the dimensional tolerance of the billet after roll forging is ±0.8mm.

[0018] The advantages of this invention's hot forging process for automotive guide arms are: it eliminates the need for various grades and thicknesses of steel, requiring only standard round steel for production, thus reducing material procurement and inventory costs. The automated continuous production process significantly reduces the production floor space, and the minimal manual intervention in each step significantly lowers labor costs. The hot forging process refines the metal grains and densifies the microstructure, avoiding joint defects common in welding processes, resulting in products with superior strength and durability compared to traditional welded parts. The one-piece forming process reduces cumbersome steps such as cutting and welding, shortening the production time per unit and meeting the demands of large-scale production. Detailed Implementation

[0019] The present invention will now be described in detail with reference to specific embodiments.

[0020] The key parameters of the cavity and the die material for bending / pre-forging / final forging dies are as follows:

[0021] 1. Cavity parameters: Bending cavity: fillet radius 3-6mm (3-4mm for 45# steel, 4-6mm for 20CrMnTi), draft angle 1-3°; Pre-forging / final forging cavity: dimensional tolerances are increased by 0.5-1mm from the finished product tolerance (e.g., the pre-forging cavity size of the medium guide arm is 55.5×32.5mm, tolerance ±0.3mm), cavity surface roughness Ra≤0.8μm;

[0022] 2. Mold material: H13 hot work die steel, pretreated hardness HRC44-48, mold service life ≥50,000 pieces;

[0023] 3. Modular solution: Quick-change cavity inserts are used, which are fixed by M16×50 hexagon socket bolts (strength grade 8.8) and φ10mm locating pins (tolerance H7 / m6). The insert replacement time is ≤30min, which is compatible with guide arms of different vehicle models.

[0024] The steps for controlling oxide scale thickness are as follows:

[0025] 1. Pretreatment before heating: Spray RD-1 type anti-oxidation coating on the surface of round steel, with a coating thickness of 10-15μm, and dry at 120-150℃ for 30min;

[0026] 2. Heating process control: Argon gas (purity ≥99.99%) is introduced into the medium frequency furnace at a flow rate of 5-8 L / min, and a slight positive pressure (0.02-0.05 MPa) is maintained inside the furnace.

[0027] 3. Post-heating treatment: Before roll forging, the oxide scale is removed by a high-pressure water descaling device (water pressure 15-20MPa, water temperature 20-30℃, nozzle angle 30-45°). After descaling, the oxide scale thickness is ≤0.3mm.

[0028] Insulation measures and transfer time during billet transportation:

[0029] 1. Insulation device: A chain conveyor with an aluminum silicate cotton insulation layer (thickness 50-80mm) is used to maintain the inner wall temperature of the conveyor at 850-900℃;

[0030] 2. Transfer time limits: From roll forging to bending process: ≤30s (billet temperature ≥850℃); From pre-forging to final forging process: ≤20s (billet temperature ≥800℃);

[0031] 3. Temperature monitoring: Infrared thermometers (measurement accuracy ±5℃) are installed at the inlet / outlet of the conveyor. When the temperature is lower than the threshold, an alarm will be automatically triggered and the production line will be suspended.

[0032] Example 1

[0033] Small car guide arm (suitable for compact cars)

[0034] (1) Raw material selection: No. 45 round steel, 60mm in diameter and 350mm in length;

[0035] (2) Heating process: The heating temperature of the medium frequency furnace is 1100℃, the heating rate is 4℃ / s, the holding time is 8min, and the oxide scale thickness is controlled within 0.3mm;

[0036] (3) Roll forging billet: The roller speed of the roll forging machine is 15r / min, the roller gap is 30mm, the roll forging is done in one pass, the billet cross-section size is 40mm×25mm, and the dimensional tolerance is ±0.5mm;

[0037] (4) Forming process: 8000T high-energy press bending stroke speed 35mm / s, pre-forging 22mm / s, final forging 18mm / s, pressure holding time for each process 2s;

[0038] (5) Edge trimming and correction: The 1600T electric screw press has an edge trimming pressure of 800T and a correction pressure of 500T. The straightness error of the finished product is ≤0.2mm / m, which is suitable for compact cars with a wheelbase of 2600-2700mm.

[0039] Subsequent heat treatment scheme

[0040] After forging, No. 45 steel is subjected to "normalizing treatment": heating temperature 860-880℃, holding for 30 minutes, air cooling, hardness HB180-220 after normalizing, grain size ≥7.

[0041] This embodiment has been verified on an actual production line. The production time for a single piece is only 4.2 minutes, and the daily output of a single production line can reach more than 2,000 pieces, meeting the "high-frequency mass production" requirements of compact cars. According to GB / T 228.1-2021, the tensile strength of the finished product reaches 702MPa. After heating in the medium frequency furnace, the oxide scale thickness is controlled within 0.3mm. According to GB / T1031-2009 "Surface Roughness Parameters and Their Values", the surface roughness Ra≤1.6μm, and no additional grinding process is required.

[0042] Example 2

[0043] Medium-sized automotive guide arm (suitable for medium-sized sedans / light SUVs)

[0044] (1) Raw material selection: 40Cr round steel, 80mm in diameter and 420mm in length;

[0045] (2) Heating process: The heating temperature of the medium frequency furnace is 1120℃, the heating rate is 6℃ / s, the holding time is 12min, and the oxide scale thickness is ≤0.4mm;

[0046] (3) Roll forging billet: The roller speed of the roll forging machine is 22r / min, the roller gap is 50mm, the roll forging is carried out in 2 passes, the billet cross-section size is 55mm×32mm, and the dimensional tolerance is ±0.6mm;

[0047] (4) Forming process: 8000T high-energy press bending stroke speed 30mm / s, pre-forging 20mm / s, final forging 15mm / s, pressure holding time for each process 3s;

[0048] (5) Edge trimming and correction: edge trimming pressure 1000T, correction pressure 650T, finished product straightness error ≤0.25mm / m, suitable for medium-sized cars and light SUVs with wheelbase of 2700-2900mm.

[0049] Subsequent heat treatment scheme

[0050] 40Cr is subjected to "quenching and tempering treatment" after forging: quenching at 840-860℃ (holding for 40min, oil cooling), tempering at 550-580℃ (holding for 60min, air cooling), hardness HB220-250, yield strength ≥650MPa.

[0051] This embodiment uses 40Cr material with precise heating at 1120℃. Tested according to GB / T229-2020, its impact toughness reaches 112J / cm². Two-pass roll forging controls the billet dimensional tolerance to ±0.6mm, requiring only 1.2mm for subsequent machining (compared to 2.5mm for existing forging processes). The production space requires only 280㎡, ​​suitable for the "limited factory space" needs of small and medium-sized car manufacturers. Furthermore, the automated process eliminates the need for manual handling. After three months of continuous production verification, the finished product dimensional fluctuation range is ≤0.15mm.

[0052] Example 3

[0053] Large automotive guide arm (suitable for mid-to-large SUVs / commercial vehicles)

[0054] (1) Raw material selection: 20CrMnTi round steel, diameter 120mm, length 500mm;

[0055] (2) Heating process: The heating temperature of the medium frequency furnace is 1150℃, the heating rate is 9℃ / s, the holding time is 18min, and the oxide scale thickness is ≤0.5mm;

[0056] (3) Roll forging billet: The roller speed of the roll forging machine is 30r / min, the roller gap is 80mm, the roll forging is carried out in 3 passes, the billet cross section size is 70mm×45mm, and the dimensional tolerance is ±0.8mm;

[0057] (4) Forming process: 8000T high-energy press bending stroke speed 25mm / s, pre-forging 18mm / s, final forging 12mm / s, pressure holding time for each process 5s;

[0058] (5) Edge trimming and correction: edge trimming pressure 1200T, correction pressure 800T, finished product straightness error ≤0.3mm / m, suitable for medium and large SUVs with a wheelbase of 2900mm or more, as well as light trucks, pickups and other commercial vehicles.

[0059] Subsequent heat treatment scheme

[0060] 20CrMnTi is subjected to "carburizing and quenching tempering" after forging: carburizing temperature 920-940℃ (holding for 4 hours, carburized layer depth 0.8-1.2mm), quenching 850℃ (holding for 20 minutes, oil cooling), tempering 200℃ (holding for 60 minutes, air cooling), surface hardness HRC58-62, core hardness HRC30-35.

[0061] This embodiment uses 20CrMnTi material, heated to 1150℃ and forged in 3 passes, to refine the grain to grade 8 (GB / T6394-2017 "Method for Determination of Average Grain Size of Metals"), achieving a fatigue life of 1.4×10⁻⁶. 6 The process involves a 5-second pressure holding process using an 8000T high-energy press to ensure that 120mm diameter round steel is formed in one go, avoiding the defects of "segmented forging and weld splicing" in the existing forging process; the cutting pressure is precisely controlled at 1200T, with a flash allowance of only 2.3mm (the existing process requires 4.5mm).

[0062] The straightness error is ≤0.3mm / m, and the assembly gap with the chassis suspension of medium and large SUVs is controlled within 0.5-0.8mm (industry requirement ≤1.2mm). After low temperature (-30℃) environmental testing, the impact toughness of the finished product still remains at 105J / cm², making it suitable for commercial vehicles used in cold northern regions.

[0063] Example 4

[0064] High wear-resistant automotive guide arm (suitable for vehicles with complex road conditions)

[0065] (1) Raw material selection: 20CrMnTi round steel, 100mm in diameter and 480mm in length;

[0066] (2) Heating process: The heating temperature of the medium frequency furnace is 1130℃, the heating rate is 7℃ / s, the holding time is 15min, and the oxide scale thickness is ≤0.4mm;

[0067] (3) Roll forging billet: The roller speed of the roll forging machine is 25r / min, the roller gap is 65mm, the roll forging is carried out in 2 passes, the billet cross-section size is 60mm×38mm, and the dimensional tolerance is ±0.7mm;

[0068] (4) Forming process: 8000T high-energy press bending stroke speed 28mm / s, pre-forging 20mm / s, final forging 14mm / s, pressure holding time for each process 4s;

[0069] (5) Edge trimming and correction: edge trimming pressure 1100T, correction pressure 700T, the finished product hardness reaches HRC28-32 after heat treatment, suitable for vehicles with complex road conditions such as mountainous areas and mining areas.

[0070] The finished product in this embodiment has a hardness of HRC28-32 after heat treatment. According to GB / T12444.2-2006, a wear test of 500 revolutions was conducted, and the wear depth was only 0.06mm.

[0071] The 1130℃ heating and 4s holding pressure process ensures that the internal structure of the forging is free of porosity defects. According to GB / T228.1-2021 testing, the tensile strength is 936MPa, the yield strength is 888MPa, and the impact toughness reaches 125J / cm², thus solving the contradiction of "high hardness and easy brittle fracture" in existing wear-resistant guide arms.

[0072] Conditioning:

[0073] 1. Quenching process: Heating temperature 850-880℃, holding time 40-60min (calculated based on a round steel diameter of 100mm, extend the holding time by 5min for every 10mm increase in diameter), cooling medium is 20# machine oil (oil temperature controlled at 30-50℃), hardness after quenching HRC58-62;

[0074] 2. Tempering process: heating temperature 580-620℃, holding time 60-90min, air cooling to room temperature, hardness after tempering HRC28-32;

[0075] 3. Quality inspection: Metallographic examination is required after tempering to ensure that the martensite grade is ≤3 (GB / T13320-2007).

[0076] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. An automated hot-forging forming method of an automobile guide arm, characterized by: The method comprises the following steps: (1) selecting round steel of 45#, 40Cr or 20CrMnTi material as raw material, feeding into a medium frequency furnace for heating, and controlling the heating temperature to be 1100-1150℃; (2) adopting a 1000mm-diameter roll forging machine to roll forge the heated round steel for 1-3 passes to obtain a blank with a preset cross-sectional shape; (3) sequentially completing bending, pre-forging and final forging forming processes through an 8000T high-energy press, and the pressure maintaining time of each process being 2-5s; (4) utilizing a 1600T electric screw press to trim and correct the formed workpiece, and the linear error of the corrected workpiece being ≤0.3mm / m to obtain a finished automobile guide arm.

2. The automated hot-forging forming method of claim 1, wherein, In the step (1), the heating rate of the medium frequency furnace is 4-9℃ / s, the round steel is kept for 8-18min, and the diameter of the round steel is 60-120mm.

3. The automated hot-forging forming method of claim 2, wherein, In the step (2), the roller rotating speed of the roll forging machine is 15-30r / min, and the roller gap adjusting range is 30-80mm.

4. The automated hot-forging forming method of claim 3, wherein, In the step (3), the press stroke speed of the bending process is 25-35mm / s, the pre-forging process is 18-22mm / s, and the final forging process is 12-18mm / s.

5. The automated hot-forging forming method of claim 4, wherein, In the step (4), the pressure of the trimming process is 800-1200T, and the pressure of the correcting process is 500-800T.

6. The automated hot-forging forming method of claim 5, wherein, The thickness of the round steel surface oxide after heating is ≤0.5mm, and the blank size tolerance after roll forging is ±0.8mm.