Manufacturing process of piston rod for shock absorber of passenger car

Abstract

The invention discloses a piston rod technology, and aims to provide a manufacturing process of a piston rod for a passenger car shock absorber, and the manufacturing process is characterized by comprising the following steps: S1, material selection: selecting a high-strength, high-toughness and corrosion-resistant titanium alloy as a piston rod base material, pretreating the selected titanium alloy base material, removing surface oxide skin, oil stains and impurities, and preparing the piston rod base material; the microstructure of the base material is observed through a metallographic microscope, so that the grain size in the microstructure is uniform, and impurities and pore defects are avoided; s2, carrying out structure topology optimization design; s3, precision forging; s4, ultra-precision machining is carried out; s5, vacuum heat treatment; s6, surface treatment; s7, performing chromium plating and micro-crack treatment; s8, hydrogen removal treatment after plating; s9, deburring treatment is carried out; s10, comprehensive quality inspection; the invention is applicable to the technical field of piston rods.

Description

TECHNICAL FIELD

[0001] The present application relates to a piston rod technology, more particularly, it relates to a manufacturing process of a piston rod for a passenger car shock absorber. BACKGROUND

[0002] In the fields of modern transportation, engineering machinery, industrial equipment, etc., as a core bearing and buffering component, the performance of the shock absorber is directly related to the stability, safety and service life of the equipment operation, and also plays a key role in driving comfort, work efficiency and even environmental impact. With the upgrading of global manufacturing industry to high-end and fine, the performance requirements of the shock absorber continue to improve, not only need to maintain long-term reliable damping effect under complex working conditions, but also need to consider lightweight, corrosion resistance and cost controllability, which is particularly prominent in the automobile, rail transportation, heavy machinery and other industries. The traditional shock absorber often faces problems such as insufficient strength, easy corrosion and aging, and damping efficiency decay, resulting in increased equipment maintenance frequency, increased use cost, and even safety hazards. SUMMARY

[0003] In view of the deficiencies in the prior art, the purpose of the present application is to provide a manufacturing process of a piston rod for a passenger car shock absorber.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a manufacturing process of a piston rod for a passenger car shock absorber, comprising the following steps:

[0005] S1, material selection: selecting high-strength, high-toughness and corrosion-resistant titanium alloy as the piston rod base material, pretreating the selected titanium alloy base material to remove surface oxide scale, oil stains and impurities, observing the microstructure of the base material by metallographic microscope to ensure that the grain size in the microstructure is uniform and there is no impurity and porosity defect;

[0006] S2, structure topology optimization design: based on finite element analysis technology, the length, diameter, wall thickness and thread parameters of the piston rod are optimized and designed, the streamline cross section and micro-rib reinforcement technology are adopted, the three-dimensional model of the piston rod is constructed, the stress distribution state of the piston rod under impact load is simulated by simulation, it is judged whether the stress distribution is uniform and the maximum stress value is not more than the allowable stress of the base material, and whether the lightweight design target is achieved is verified, if both items are satisfied, go to S3, if any one is not satisfied, adjust the design parameters and simulate again;

[0007] S3, precision forging: the pretreated titanium alloy base material is placed into a forging device, the forging temperature, forging pressure and forging speed are controlled, and the base material is subjected to precision forging treatment to form a piston rod blank. After forging, the key dimensions of the blank are measured by a size detection tool to determine whether they meet the design tolerance requirements. At the same time, ultrasonic flaw detection technology is used to detect whether there are cracks, porosity and other defects inside the blank. If the dimensions are qualified and there are no internal defects, proceed to S4. If any of the dimensions are unqualified, the blank is repaired or scrapped;

[0008] S4, ultra-precision machining: turning, milling, grinding and threading are performed on the forged piston rod blank. The cutting speed, cutting depth and feed rate during machining are controlled. After machining, the outer diameter of the piston rod is measured by a laser diameter gauge, and the surface roughness is detected by a surface roughness meter to determine whether the dimensional accuracy and surface quality meet the preset standards. If they do, proceed to S5. If they do not, adjust the machining parameters and re-machine.

[0009] S5, vacuum heat treatment: the machined piston rod is placed in a vacuum heat treatment furnace for quenching and tempering. The quenching temperature, holding time, cooling rate and tempering temperature are controlled. After heat treatment, the hardness of the piston rod is measured by a Rockwell hardness tester, and the microstructure is observed by a metallographic microscope to ensure that the hardness and microstructure meet the requirements, with a hardened layer depth of 0.6-1.0mm and a hardness of 50-57HRC.

[0010] S6, surface treatment: first, the piston rod is subjected to anodic oxidation treatment, with a current density of 1-3A / dm 2 and a treatment time of 20-40min to form a dense oxide film. Then, according to the design requirements, vacuum evaporation treatment is performed, with the selected metals including but not limited to titanium or aluminum or copper, an evaporation temperature of 100-200°C and an evaporation time of 30-60min to form a uniform metal film. After treatment, the film thickness is measured by a coating thickness gauge, and the film adhesion is tested by an adhesion test tool to determine whether the film thickness is uniform and the adhesion meets the standards. If it does, proceed to S7. If it does not, re-surface treatment is performed.

[0011] S7, chrome plating and micro-crack treatment: the surface-treated piston rod is subjected to micro-crack chrome plating treatment, with the chrome plating process parameters controlled to ensure uniform plating layer thickness. After chrome plating, the number of micro-cracks is observed by a microscope, and the plating layer hardness is detected by a hardness tester to determine whether the number of micro-cracks and the plating layer hardness meet the requirements. If they do, proceed to S8. If they do not, re-plating is performed.

[0012] S8, hydrogen removal treatment after plating: the piston rod after plating is placed in a hydrogen removal furnace, the hydrogen removal temperature is controlled to be 180-220 DEG C, the holding time is 2-4h, after hydrogen removal is completed, whether the piston rod exists hydrogen embrittlement risk is detected by using eddy current detection technology: the conductivity of the piston rod sigma is detected, the preset conductivity standard value sigma0, if sigma >= sigma0*90%, then it is judged that the hydrogen removal treatment is qualified;If sigma < sigma0*90%, then the holding time is prolonged by 1-2h, sigma is detected again, if it is still not up to standard, then the hydrogen removal treatment is carried out again;

[0013] S9, deburring treatment: the mechanical deburring and the electrochemical deburring are combined, and the edge, thread and the like of the piston rod are subjected to deburring treatment, after the treatment, the surface of the piston rod is observed by using a magnifying glass, whether there is burr and sharp edge is judged, if it is qualified, then S10 is converted, if it is not qualified, then the burr is removed again;

[0014] S10, comprehensive quality inspection: the tensile test is carried out by using a universal material testing machine, the mechanical properties of the piston rod are detected;The non-destructive testing is carried out by using ultrasonic flaw detection and eddy current detection technology, the internal and surface defects are detected;The torque tester is used to detect the outer hexagonal torque of the outer connecting end, whether all indexes meet the industry standard and design requirement is judged, if all meet, then it is judged as qualified product, if there is any unqualified, then it is judged as unqualified product, and the rework or scrap treatment is carried out.

[0015] The application is further provided that: in the S3, the ratio of the forging temperature to the phase transition temperature of the titanium alloy base material is 0.8-0.9:1, and the ratio of the forging pressure to the yield strength of the base material is 1.2-1.5:1.

[0016] The application is further provided that: in the S5, the quenching temperature Ta and the tempering temperature Tb are adjusted by a dynamic compensation model: when the furnace pressure < preset threshold P1, Ta is adjusted up by 5-10 DEG C and Tb is adjusted down by 5-8 DEG C;When the furnace pressure > P1, Ta is adjusted down by 5-10 DEG C and Tb is adjusted up by 5-8 DEG C, after compensation, the temperature curve is monitored again until stable.

[0017] The application is further provided with: in the S4, the control method in the ultra-precision machining process comprises: setting a temperature detection module, a pressure detection module, a cutting parameter acquisition module and a tool wear detection module on the machining equipment, the temperature detection module monitors the machining area temperature T in real time, the pressure detection module monitors the cutting force F in the cutting process in real time, the cutting parameter acquisition module acquires the cutting speed V and the cutting depth A, and the tool wear detection module detects the tool wear W; presetting a temperature danger threshold T1, a temperature early warning threshold T2, and T2 < T1, a cutting force standard range [Fmin, Fmax], and a maximum allowable tool wear Wmax; when T > T1, the machining is immediately stopped and an alarm signal is sent out; when T2 < T ≤ T1, a temperature too high early warning is sent out, the cutting power P = k × V × A is calculated according to V and A acquired by the cutting parameter acquisition module, k is a preset coefficient, the preset cutting power-temperature relationship curve is called, the corresponding standard temperature T0 is inquired based on the current P, if the current T ≤ T0 + ΔT, ΔT is a preset temperature deviation allowable value, only the cutting speed V is adjusted to V1 = V × (T0 / T), and after the adjustment, the monitoring is continuously performed in a t1 time period; if T > T2 or F ∉ [Fmin, Fmax] in the t1 time period, the machining is temporarily stopped, the tool wear W is detected by the tool wear detection module, if W ≤ Wmax, the machining is restarted after a new tool of the same type is replaced, T and F are detected again, if T ≤ T2 and F ∈ [Fmin, Fmax], it is determined that the adjustment is effective, and the monitoring is continuously performed; if T > T2 or F ∉ [Fmin, Fmax] after the tool is replaced, it is determined that the cutting parameter adjustment is invalid, a cooling liquid adjustment system is started, the cooling liquid adjustment system comprises a flow adjustment module and a temperature adjustment module, the cooling liquid flow is adjusted to Q1 = Q0 × (T / T0) by the flow adjustment module, Q0 is an initial cooling liquid flow, the cooling liquid temperature is reduced to Ts = 20℃ + (T0-T) / 2 by the temperature adjustment module, the monitoring is continuously performed in a t2 time period after the adjustment, if T ≤ T2 and F ∈ [Fmin, Fmax] in the t2 time period, it is determined that the cooling liquid adjustment is effective, the machining is continuously performed and monitored; if the requirements are not met in the t2 time period, the machining is stopped and equipment failure is checked; if the current T > T0 + ΔT, the cooling liquid adjustment system is directly started, and the cutting depth A is adjusted to A1 = A × (T0 / T).

[0018] The application is further provided with: in the S7, the control method in the chrome plating and micro-crack treatment process comprises: setting a plating layer thickness detection module, a micro-crack counting module, a hardness detection module, an adhesion detection module and a defect detection module; first, the plating layer thickness d is measured by the plating layer thickness detection module, a standard thickness range [0.015, 0.025] is preset, if then the chromium plating current density and the chromium plating time are adjusted, and after adjustment, the measurement is re-performed until d is in the range of [0.015, 0.025]; when d is in the range of [0.015, 0.025], the number of micro-cracks n in a unit length is detected by a micro-crack counting module, a preset standard number n0 is 400 strips per centimeter, and an allowable deviation is ±5%; if then the cooling speed after chromium plating and the stress release process are adjusted, and after adjustment, the detection is re-performed until n is in the range of [n0*95%, n0*105%]; subsequently, the hardness HV of the plating layer is detected by a hardness detection module, a preset standard hardness range is [800, 1200], and if then the chromium plating process parameters are returned to be adjusted, and the chromium plating treatment is re-performed; when n and HV both meet the requirements, a cross-cut test and a thermal shock test are performed by an adhesion detection module; after the cross-cut test, a magnifying glass is used to observe whether the plating layer falls off; the thermal shock test cycles the piston rod in the range of -40 DEG C to 120 DEG C for 5 times, and each time is kept for 30 min; after the test, it is detected whether the plating layer falls off; meanwhile, an industrial camera and an image processing technology are used to detect, by a defect detection module, whether there are micro spots and damage defects on the surface of the plating layer; a defect area threshold S0 is set; if it is found by image processing that a defect area S is greater than or equal to S0, it is determined that the product is unqualified, and the chromium plating is re-performed; if the adhesion detection has no falling off and S is less than S0, it is determined that the plating layer is qualified; d, n, HV, the adhesion detection result and S are substituted into a preset comprehensive score formula: K=0.3*(d / d0)+0.25*(n / n0)+0.2*(HV / HV0)+0.15*A+0.1*(1-S / S0), wherein d0 is a standard thickness intermediate value, HV0 is a standard hardness intermediate value, A is an adhesion detection coefficient, A=1 when there is no falling off, and A=0 when there is falling off, and a comprehensive score K is calculated; if K is greater than or equal to 0.9, it is determined that the chromium plating and the micro-crack treatment are qualified, and S8 is entered; if 0.8

[0019] The application further provides that in S2, when the structural topology optimization design is performed, the ratio of the curvature radius of the streamline section to the piston rod diameter is 0.3-0.4:1, and the ratio of the height of the micro rib to the piston rod wall thickness is 0.1-0.15:1.

[0020] The application further provides that in S9, the mechanical deburring adopts a grinding wheel to grind, the rotating speed of the grinding wheel is 1000-1500 r / min, the grinding time is 5-10 min, the voltage of the electrochemical deburring is 10-20 V, and the processing time is 3-8 min; after the deburring, a magnifying glass is used to observe the surface of the piston rod to ensure that there is no burr and no sharp edge, and the surface roughness Ra is less than or equal to 0.8 microns.

[0021] The application is further provided that: in the S10, the tensile speed of the tensile test is 2-5mm / min, when the tensile strength of the piston rod is greater than or equal to 1000MPa, the yield strength is greater than or equal to 800MPa, and the elongation is greater than or equal to 10%, the mechanical properties are determined to be qualified; when the external hexagonal torque is detected, the torque tester is used to gradually apply torque, and when the torque value is stable and greater than 70N / m, the torque is determined to be qualified, and all detection items are qualified, and the product can be shipped.

[0022] The beneficial effects of the application are:

[0023] 1. Compared with the prior art, the manufacturing process of the piston rod for passenger car shock absorber of the application realizes fine control through the whole process, from substrate selection to comprehensive quality inspection to form a closed loop; titanium alloy substrate ensures high strength and corrosion resistance, structure topology optimization realizes lightweight and uniform stress distribution, precise forging and ultra-precision machining guarantee size accuracy, multi-channel surface treatment and chrome plating process improve wear resistance and adhesion, hydrogen removal treatment avoids hydrogen embrittlement risk, deburring ensures safety in use, and comprehensive quality inspection covers key indicators such as mechanical properties and defect detection; effectively solve the problems of size deviation, surface defects and insufficient mechanical properties in traditional process, the produced piston rod has the characteristics of lightweight, high toughness, corrosion resistance and long service life, and fully meets the harsh working condition requirements of shock absorber, significantly improves the stability and reliability of the damping system.

[0024] 2. In the S3 of the manufacturing process of the piston rod for passenger car shock absorber of the application, the ratio of forging temperature to phase transition temperature is 0.8-0.9:1, if less than 0.8:1, the plasticity of titanium alloy substrate is insufficient, cracks and folding defects are easy to occur during forging, and it is difficult to form uniform grains; if greater than 0.9:1, the substrate is prone to coarse grains, resulting in decreased mechanical properties of the piston rod and weakened impact resistance; and the ratio of forging pressure to yield strength is 1.2-1.5:1, when less than 1.2:1, the substrate is not fully formed, the size accuracy of the blank is insufficient, and there may be porosity inside; when greater than 1.5:1, the substrate is prone to excessive deformation, resulting in residual stress, and deformation cracking is easy to occur during subsequent processing; the above ratio precisely matches the characteristics of titanium alloy, which not only ensures the full formation of the blank, but also avoids abnormal grains and residual stress, thereby ensuring the quality of the piston rod blank and the feasibility of subsequent processing.

[0025] 3. In the present application, the quenching and tempering temperature is adjusted by a dynamic compensation model in S5, and the parameters are optimized in real time according to the pressure fluctuation in the furnace, solving the problem of unstable heat treatment effect caused by pressure change in the fixed temperature process; when the pressure in the furnace is lower than P1, the quenching temperature is raised and the tempering temperature is lowered to avoid insufficient quenching layer depth and low hardness caused by insufficient pressure; when the pressure is higher than P1, the quenching temperature is lowered and the tempering temperature is raised to prevent overheating, which leads to coarse grains and decreased toughness; this dynamic adjustment mechanism ensures that the quenching layer depth of the piston rod is stable at 0.6-1.0mm, the hardness is maintained at 50-57HRC, the microstructure is uniform, the mechanical properties are consistent, and the defects such as unqualified hardness and insufficient toughness caused by pressure fluctuation are effectively avoided, improving the stability of the heat treatment process and the product qualification rate.

[0026] 4. In the present application, the multi-module monitoring and self-adaptive adjustment system of ultra-precision machining in S4 can real-time control key parameters such as machining temperature, cutting force and tool wear; when the temperature exceeds the threshold, it can alarm or adjust the cutting speed and cooling liquid parameters in time to avoid workpiece deformation and poor surface quality caused by high temperature; when the cutting force is abnormal or the tool wear exceeds the limit, the machining precision is ensured by tool replacement or parameter adjustment to prevent size deviation and surface roughness exceeding the standard caused by tool problems; this control method solves the problem of fixed parameters in traditional machining and cannot respond to real-time changes, ensuring the accuracy of the piston rod outer diameter size and the surface roughness, and the thread machining precision meets the requirements, laying a good foundation for subsequent surface treatment and assembly, and significantly improving the machining efficiency and product machining quality stability. BRIEF DESCRIPTION OF DRAWINGS

[0027] Fig. 1 The flowchart of the manufacturing process of the piston rod for passenger car shock absorber of the present application.

[0028] Fig. 2 The structure diagram of the piston rod for passenger car shock absorber of the present application. DETAILED DESCRIPTION

[0029] REFERENCE Figs. 1-2 The manufacturing process of the piston rod for passenger car shock absorber of the present application is further described.

[0030] For ease of description, spatially relative terms, such as "upper", "lower", "left", "right", and the like, can be used herein for the purpose of illustrating one element or feature's relationship to another element or feature, as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation, in addition to the orientation depicted in the figures. For example, if a device in the figures is inverted, elements described as being on the "lower" side of other elements or features would then be oriented on "upper" sides thereof, and vice versa. Thus, the exemplary term "lower" can encompass both an orientation of upper and lower. The devices can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

[0031] Also, the terms "first", "second", and the like, herein do not necessarily have to refer to quantities, but can be used to differentiate one component from another, by the relative name.

[0032] Figs. 1-2 The manufacturing process of a passenger car shock absorber piston rod shown comprises the following steps:

[0033] S1, material selection: selecting high-strength, high-toughness, corrosion-resistant titanium alloy as the piston rod base material, pretreating the selected titanium alloy base material to remove surface oxide scale, oil stains and impurities, observing the microstructure of the base material by metallographic microscope to ensure that the grain size in the microstructure is uniform and there are no impurities and porosity defects;

[0034] S2, structure topology optimization design: based on finite element analysis technology, the length, diameter, wall thickness and thread parameters of the piston rod are optimized and designed, the streamline cross section and micro-rib reinforcement technology are adopted, the three-dimensional model of the piston rod is constructed, the stress distribution state of the piston rod under impact load is simulated, it is judged whether the stress distribution is uniform and the maximum stress value does not exceed the allowable stress of the base material, and it is verified whether the lightweight design target is achieved, if both items are satisfied, go to S3, if any one item is not satisfied, adjust the design parameters and simulate again;

[0035] S3, precision forging: the pretreated titanium alloy base material is put into the forging equipment, the forging temperature, forging pressure and forging speed are controlled, the base material is subjected to precision forging treatment, the piston rod blank is formed, after forging is completed, the key dimensions of the blank are measured by size detection tool to judge whether it meets the design tolerance requirement, at the same time, ultrasonic flaw detection technology is used to detect whether there are cracks, porosity and other defects inside the blank, if the size is qualified and there is no internal defect, go to S4, if there is any unqualified item, the blank is repaired or scrapped;

[0036] S4, ultra-precision machining: turning, milling, grinding and threading processing are performed on the forged piston rod blank, the cutting speed, cutting depth and feed rate in the machining process are controlled, after the machining is completed, the outer diameter size of the piston rod is measured by using a laser diameter measuring instrument, the surface roughness is detected by using a surface roughness instrument, whether the size precision and surface quality meet the preset standard is judged, if yes, S5 is turned to, if not, the machining parameters are adjusted and the machining is re-performed;

[0037] S5, vacuum heat treatment: the machined piston rod is put into a vacuum heat treatment furnace, quenching and tempering treatment is performed, the quenching temperature, holding time, cooling speed and tempering temperature are controlled, after the heat treatment is completed, the hardness of the piston rod is detected by using a Rockwell hardness tester, the microstructure is observed by using a metallographic microscope, it is ensured that the hardness and microstructure meet the requirements, wherein the hardened layer depth is 0.6-1.0mm, the hardness is 50-57HRC;

[0038] S6, surface treatment: first, the piston rod is subjected to anodic oxidation treatment, wherein the current density is 1-3A / dm 2 , the treatment time is 20-40min, a dense oxide film is formed, then vacuum evaporation treatment is performed according to the design requirements, wherein the metals selected in the vacuum evaporation treatment include but are not limited to titanium or aluminum or copper, the evaporation temperature is 100-200℃, the evaporation time is 30-60min, a uniform metal film is formed, after the treatment is completed, the film thickness is measured by using a coating thickness gauge, the film adhesion is detected by using an adhesion testing tool, whether the film thickness is uniform and the adhesion meets the standard is judged, if yes, S7 is turned to, if not, the surface treatment is re-performed;

[0039] S7, chrome plating and micro-crack treatment: the piston rod after the surface treatment is subjected to micro-crack chrome plating treatment, the chrome plating process parameters are controlled, it is ensured that the plating layer thickness is uniform, after the chrome plating is completed, the number of micro-cracks is observed by using a microscope, the plating layer hardness is detected by using a hardness tester, whether the number of micro-cracks and the plating layer hardness meet the requirements is judged, if yes, S8 is turned to, if not, the chrome plating is re-performed;

[0040] S8, hydrogen removal treatment after plating: the piston rod after the chrome plating is put into a hydrogen removal furnace, the hydrogen removal temperature is controlled to be 180-220℃, the holding time is 2-4h, after the hydrogen removal is completed, whether the piston rod has hydrogen embrittlement risk is detected by using eddy current detection technology: the conductivity σ of the piston rod is detected, a preset conductivity standard value σ0 is set, if σ≥σ0×90%, it is determined that the hydrogen removal treatment is qualified; if σ<σ0×90%, the holding time is extended by 1-2h, σ is detected again, if it is still not up to the standard, the hydrogen removal treatment is re-performed;

[0041] S9, deburring treatment: adopt the mechanical deburring and electrochemical deburring to combine the way, to the edge and corner, thread and so on of the piston rod deburring treatment, after the treatment, adopt the magnifying glass to observe the piston rod surface, judge whether no burr, no sharp edge, if meet, then turn S10, if not meet, then re-deburring;

[0042] S10, comprehensive quality inspection: adopt the universal material testing machine to carry out the tensile test, detect the mechanical properties of the piston rod; adopt the ultrasonic flaw detection and eddy current detection technology to carry out the non-destructive testing, detect the internal and surface defects; adopt the torque tester to detect the outer hexagonal torque of the external connection end, judge whether all indexes meet the industry standard and design requirement, if all meet, judge as qualified product, if any one is unqualified, judge as unqualified product, carry out the rework or scrap treatment;

[0043] The manufacturing process forms a closed loop through the fine control of the whole process from the selection of the base material to the comprehensive quality inspection; the titanium alloy base material ensures high strength and corrosion resistance, the structure topology optimization realizes lightweight and uniform stress distribution, the precision forging and ultra-precision machining guarantee the dimensional accuracy, the multi-channel surface treatment and chrome plating process improve the wear resistance and adhesion, the hydrogen removal treatment avoids the risk of hydrogen embrittlement, the deburring guarantees the safety in use, and the comprehensive quality inspection covers the key indicators such as mechanical properties and defect detection; effectively solve the problems such as size deviation, surface defects and insufficient mechanical properties in traditional process, the produced piston rod has the characteristics of lightweight, high toughness, corrosion resistance and long service life, fully meets the harsh working condition requirements of shock absorber, and significantly improves the stability and reliability of the shock absorption system.

[0044] In the S3, the ratio of the forging temperature to the phase transition temperature of the titanium alloy base material is 0.8-0.9:1, and the ratio of the forging pressure to the yield strength of the base material is 1.2-1.5:1;

[0045] The ratio of the forging temperature to the phase transition temperature in S3 is set to 0.8-0.9:1, if less than 0.8:1, the titanium alloy base material is insufficient in plasticity, cracks and folding defects are easy to occur during forging, and it is difficult to form uniform grains; if greater than 0.9:1, the base material is easy to have coarse grains, resulting in the decrease of the mechanical properties of the piston rod and the weakening of the impact resistance; and the ratio of the forging pressure to the yield strength is 1.2-1.5:1, when less than 1.2:1, the base material is not fully formed, the size precision of the blank is insufficient, and there are loose inside; when greater than 1.5:1, the base material is easy to be deformed excessively, resulting in residual stress, and deformation and cracking are easy to occur in subsequent processing; the above ratio is preferably selected because it accurately matches the characteristics of titanium alloy, ensures the full formation of the blank, avoids abnormal grains and residual stress, and guarantees the quality of the piston rod blank and the feasibility of subsequent processing.

[0046] In S5, the quenching temperature Ta and the tempering temperature Tb are adjusted by a dynamic compensation model: when the furnace pressure < a preset threshold P1, Ta is adjusted up by 5-10℃ and Tb is adjusted down by 5-8℃; when the furnace pressure > P1, Ta is adjusted down by 5-10℃ and Tb is adjusted up by 5-8℃, and the temperature curve is monitored again until stable after compensation;

[0047] In S5, the quenching and tempering temperatures are adjusted by a dynamic compensation model, which optimizes the parameters in real time according to the furnace pressure fluctuation, solving the problem of unstable heat treatment effect caused by pressure changes in the fixed temperature process; when the furnace pressure is lower than P1, the quenching temperature is adjusted up and the tempering temperature is adjusted down to avoid insufficient quenching layer depth and low hardness caused by insufficient pressure; when the pressure is higher than P1, the quenching temperature is adjusted down and the tempering temperature is adjusted up to prevent grain coarsening and toughness decline caused by overheating; this dynamic adjustment mechanism ensures that the piston rod quenching layer depth is stable at 0.6-1.0mm, the hardness is maintained at 50-57HRC, the microstructure is uniform, and the mechanical properties are consistent, effectively avoiding defects such as hardness unqualified and insufficient toughness caused by pressure fluctuation, and improving the stability of the heat treatment process and the product qualification rate.

[0048] In S4, the control method in the ultra-precision machining process includes: setting a temperature detection module, a pressure detection module, a cutting parameter acquisition module and a tool wear detection module on the machining equipment, the temperature detection module monitors the machining area temperature T in real time, the pressure detection module monitors the cutting force F in the cutting process in real time, the cutting parameter acquisition module acquires the cutting speed V and the cutting depth A, and the tool wear detection module detects the tool wear W; preset a temperature danger threshold T1, a temperature warning threshold T2, and T2 < T1, a cutting force standard range [Fmin, Fmax], and a maximum allowable tool wear Wmax; when T > T1, stop machining immediately and send an alarm signal; when T2 < T ≤ T1, send a temperature too high warning, calculate the cutting power P = k × V × A according to the V and A acquired by the cutting parameter acquisition module, k is a preset coefficient, and query the corresponding standard temperature T0 based on the current P by calling the preset cutting power-temperature relationship curve; if the current T ≤ T0 + ΔT, ΔT is a preset temperature deviation allowance, only adjust the cutting speed V to V1 = V × (T0 / T), and continuously monitor for a period of t1 after adjustment, if T ≤ T2 and F ∈ [Fmin, Fmax] within the period of t1, it is determined that the adjustment is effective, the current cutting parameters are maintained, and each index is continuously monitored; if T > T2 or within the period of t1, stop machining, detect the tool wear W by the tool wear detection module, if W ≤ Wmax, replace the new tool of the same type and restart machining, detect T and F again, if T ≤ T2 and F ∈ [Fmin, Fmax], it is determined that the adjustment is effective, and continuous monitoring is performed; if T > T2 or If the determination result is invalid, the cooling liquid adjusting system is started, the cooling liquid adjusting system comprises a flow adjusting module and a temperature adjusting module, the flow adjusting module adjusts the cooling liquid flow to Q1=Q0×(T / T0), Q0 is the initial cooling liquid flow, the temperature adjusting module reduces the cooling liquid temperature to Ts=20℃+(T0-T) / 2, the monitoring in the t2 period is continued after the adjustment, if T≤T2 and F∈[Fmin,Fmax] in the t2 period, it is determined that the cooling liquid adjustment is effective, the machining is continued and the monitoring is continued; if the requirements are not met in the t2 period, the machining is stopped and the equipment failure is checked; if the current T>T0+ΔT, the cooling liquid adjusting system is directly started, and the cutting depth A is adjusted to A1=A×(T0 / T);

[0049] The multi-module monitoring and self-adaptive adjusting system of the super-precision machining in S4 can control key parameters such as machining temperature, cutting force and tool wear in real time; when the temperature exceeds the threshold, the cutting speed and the cooling liquid parameter are adjusted in time to avoid workpiece deformation and surface quality deterioration caused by high temperature; when the cutting force is abnormal or the tool wear exceeds the limit, the machining precision is ensured by tool replacement or parameter adjustment to prevent size deviation and surface roughness exceeding the standard caused by tool problems; the control method solves the disadvantages of fixed parameters in traditional machining and cannot respond to real-time changes, ensures the accurate size of the outer diameter of the piston rod and the standard surface roughness, and meets the requirements of thread machining precision, thereby laying a good foundation for subsequent surface treatment and assembly and significantly improving the machining efficiency and product machining quality stability.

[0050] In S7, the control method in the chromium plating and micro-crack treatment process comprises a plating layer thickness detection module, a micro-crack counting module, a hardness detection module, an adhesion detection module and a defect detection module; first, the plating layer thickness d is measured by the plating layer thickness detection module, the preset standard thickness range is [0.015, 0.025], and if the chromium plating current density and the chromium plating time are adjusted, and after the adjustment, the measurement is restarted until d∈[0.015, 0.025]; when d∈[0.015, 0.025], the number of micro-cracks n in a unit length is detected by the micro-crack counting module, the preset standard number n0 is 400 lines / cm, the allowable deviation is ±5%, and if the cooling speed and the stress release process after chromium plating are adjusted, and after the adjustment, the detection is restarted until n∈[n0×95%, n0×105%]; then, the plating layer hardness HV is detected by the hardness detection module, the preset standard hardness range is [800, 1200], and if If the n and HV are both qualified, the cross-cut test and thermal shock test are carried out through the adhesion detection module. After the cross-cut test, the coating is observed by a magnifying glass to determine whether it falls off. In the thermal shock test, the piston rod is cycled in the range of -40 DEG C to 120 DEG C for 5 times, and each time is kept for 30 min. After the test, it is detected whether the coating falls off. At the same time, the industrial camera and image processing technology are used to detect whether there are small spots and damage defects on the surface of the coating through the defect detection module. A defect area threshold S0 is set. If the defect area S is greater than or equal to S0 after image processing, it is determined that the coating is unqualified and needs to be plated again. If there is no falling off in the adhesion detection and S is less than S0, it is determined that the coating is qualified. The d, n, HV, adhesion detection results and S are substituted into the preset comprehensive score formula: K = 0.3 x (d / d0) + 0.25 x (n / n0) + 0.2 x (HV / HV0) + 0.15 x A + 0.1 x (1-S / S0), wherein d0 is a standard thickness intermediate value, HV0 is a standard hardness intermediate value, A is an adhesion detection coefficient, A = 1 when there is no falling off, and A = 0 when there is falling off. The comprehensive score K is calculated. If K is greater than or equal to 0.9, it is determined that the plating and micro-crack treatment are qualified, and S8 is entered. If 0.8 ≤ K < 0.9, the coating is repaired and K is detected again. If K is greater than or equal to 0.9 after the repair, S8 is entered. If K is less than 0.9 after the repair, the coating is plated again. If K is less than 0.8, the coating is plated again directly.

[0051] The multi-index control and comprehensive score system of the plating and micro-crack treatment in S7 precisely controls the key parameters such as the coating thickness, the number of micro-cracks, the hardness and the adhesion. The coating thickness is controlled in the range of 0.015-0.025 mm, the number of micro-cracks meets the standard of 400 strips per centimeter ± 5%, the hardness is 800-1200 HV, and the quality of the coating is comprehensively ensured by combining the adhesion test and the defect detection. The comprehensive score formula quantifies the weight of each index, avoiding the problem that a single index is qualified but the overall performance is poor. The process solves the defects such as uneven coating thickness, uncontrollable number of micro-cracks and insufficient adhesion in the plating, the micro-crack plating layer formed has high hardness and good lubricity, the wear resistance and fatigue resistance of the piston rod are improved, the service life of the shock absorber is prolonged, the unqualified rate is reduced through the repair mechanism, and the production efficiency is improved.

[0052] In S2, when the structural topology optimization design is performed, the ratio of the curvature radius of the streamline section to the diameter of the piston rod is 0.3-0.4:1, and the ratio of the height of the micro-rib to the wall thickness of the piston rod is 0.1-0.15:1.

[0053] The ratio of the curvature radius of the streamlined section to the diameter of the piston rod in S2 is 0.3-0.4:1, if less than 0.3:1, the streamlined effect of the section is poor, the fluid resistance is large, and turbulence is easy to occur in the damping process, affecting the damping efficiency; if greater than 0.4:1, the effective bearing area of the piston rod is reduced, the mechanical strength is insufficient, and the impact load cannot be borne; and the ratio of the micro-rib height to the wall thickness is 0.1-0.15:1, when less than 0.1:1, the micro-rib strengthening effect is not obvious, and the piston rod is weak in deformation resistance; when greater than 0.15:1, the weight of the piston rod is increased, which violates the lightweight design goal, and stress concentration is easy to occur at the root of the micro-rib; the ratio design takes into account the fluid dynamics performance and structural strength, balances the lightweight and high rigidity, and improves the stability and response speed of the piston rod in the damping process.

[0054] In S9, the mechanical deburring adopts a grinding wheel to grind, the rotating speed of the grinding wheel is 1000-1500 r / min, the grinding time is 5-10 min, the voltage of the electrochemical deburring is 10-20 V, and the processing time is 3-8 min; after deburring, the piston rod surface is observed by using a magnifying glass to ensure that there is no burr, no sharp edge, and the surface roughness Ra is less than or equal to 0.8 μm;

[0055] In S9, the mechanical and electrochemical deburring are combined, the rotating speed of the grinding wheel is 1000-1500 r / min, the time is 5-10 min, the electrochemical voltage is 10-20 V, and the time is 3-8 min; the combination can completely remove the burrs at the corners and threads, and control the surface roughness Ra to be less than or equal to 0.8 μm, so as to ensure the assembly compatibility and use safety of the piston rod, avoid the sealing failure and abnormal sound of the shock absorber caused by the burr problem, and improve the overall quality of the product.

[0056] In S10, the tensile speed of the tensile test is 2-5 mm / min; when the tensile strength of the piston rod is greater than or equal to 1000 MPa, the yield strength is greater than or equal to 800 MPa, and the elongation is greater than or equal to 10%, the mechanical properties are determined to be qualified; when the torque value of the torque tester is greater than 70 N / m, the torque is determined to be qualified; and the product can be shipped out only when all the detection items are qualified.

[0057] These indexes ensure that the piston rod has sufficient bearing capacity and reliable connection; the detection standard strictly meets the working condition requirements of the shock absorber, and comprehensively verifies the mechanical properties and assembly stability of the product, so as to avoid the safety hazards such as piston rod fracture and loose connection caused by insufficient mechanical properties, and ensure the safe operation of the damping system.

[0058] The above only describes the preferred embodiments of the present application, and is not used to limit the present application, and the skilled in the art can make common changes and replacements within the technical scheme range of the present application, which should be included in the protection range of the present application.

Claims

1. A manufacturing process for a piston rod for a passenger car shock absorber, characterized in that: Comprise the following steps: S1, material selection: select high strength, high toughness, corrosion resistance titanium alloy as the piston rod base material, the selected titanium alloy base material is pretreated, the surface oxide, dirt and impurities are removed, the microstructure of the base material is observed by metallographic microscope, the grain size in the microstructure is ensured to be uniform, and there is no impurity and pore defect; S2, structure topology optimization design: based on finite element analysis technology, the length, diameter, wall thickness and thread parameters of the piston rod are optimized and designed, the streamline section and micro-rib reinforcement technology are adopted, the three-dimensional model of the piston rod is constructed, the stress distribution state of the piston rod under impact load is simulated, whether the stress distribution is uniform and the maximum stress value is not more than the allowable stress of the base material is judged, whether the lightweight design target is achieved is verified, if both items are satisfied, turn to S3, if any one is not satisfied, adjust the design parameters and simulate again; S3, precision forging: the pretreated titanium alloy base material is put into the forging equipment, the forging temperature, forging pressure and forging speed are controlled, the base material is treated by precision forging, the piston rod blank is formed, after forging, the key size of the blank is measured by size detection tool, whether it meets the design tolerance requirement is judged, at the same time, whether there is crack, looseness and other defects in the blank is detected by ultrasonic flaw detection technology, if the size is qualified and there is no internal defect, turn to S4, if there is any unqualified item, the blank is repaired or scrapped; S4, ultra-precision machining: turning, milling, grinding and thread processing are carried out on the forged piston rod blank, the cutting speed, cutting depth and feed rate in the machining process are controlled, after machining, the outer diameter size of the piston rod is measured by laser diameter measuring instrument, the surface roughness is detected by surface roughness meter, whether the size precision and surface quality meet the preset standard is judged, if it meets, turn to S5, if it does not meet, adjust the machining parameters and reprocess; S5, vacuum heat treatment: the machined piston rod is put into the vacuum heat treatment furnace, quenching and tempering treatment is carried out, the quenching temperature, holding time, cooling speed and tempering temperature are controlled, after heat treatment, the hardness of the piston rod is detected by Rockwell hardness tester, the microstructure is observed by metallographic microscope, it is ensured that the hardness and microstructure meet the requirements, the depth of hardened layer is 0.6-1.0mm, the hardness is 50-57HRC; S6, surface treatment: first, the piston rod is subjected to anodic oxidation treatment, wherein the current density is 1-3 A / dm 2 , the treatment time is 20-40 min, a dense oxide film is formed, and then vacuum evaporation treatment is performed according to design requirements, wherein the metal selected in the vacuum evaporation treatment includes but is not limited to titanium or aluminum or copper, the evaporation temperature is 100-200 DEG C, the evaporation time is 30-60 min, a uniform metal film is formed, after the treatment is completed, a coating thickness gauge is used to measure the film thickness, an adhesion testing tool is used to detect the film adhesion, whether the film thickness is uniform and the adhesion meets the standard is judged, if it meets, it is transferred to S7, if it does not meet, the surface treatment is performed again; S7, chrome plating and micro crack treatment: the surface treated piston rod is treated by micro crack chrome plating, the chrome plating process parameters are controlled, it is ensured that the plating layer thickness is uniform, after chrome plating, the number of micro cracks is observed by microscope, the plating layer hardness is detected by hardness tester, whether the number of micro cracks and the plating layer hardness meet the requirements is judged, if it meets, turn to S8, if it does not meet, replate chrome; S8, hydrogen removal treatment after plating: the piston rod after plating is put into a hydrogen removal furnace, the hydrogen removal temperature is controlled to be 180-220 DEG C, the holding time is 2-4h, after the hydrogen removal is completed, the vortex detection technology is used to detect whether the piston rod exists hydrogen embrittlement risk: the conductivity of the piston rod is detected, the preset conductivity standard value is sigma 0, if sigma >= sigma 0 * 90%, it is determined that the hydrogen removal treatment is qualified; if sigma < sigma 0 * 90%, the holding time is extended by 1-2h, sigma is detected again, if it is still not up to standard, the hydrogen removal treatment is re-performed; S9, deburring treatment: a combination of mechanical deburring and electrochemical deburring is used to deburr the corners, threads and the like of the piston rod, after the treatment is completed, the surface of the piston rod is observed by using a magnifying glass to determine whether there is no burr and no sharp edge, if it is qualified, it is transferred to S10, if it is not qualified, it is re-deburred; S10, comprehensive quality inspection: the universal material testing machine is used for tensile test to detect the mechanical properties of the piston rod; the ultrasonic flaw detection and vortex detection technology are used for non-destructive testing to detect internal and surface defects; the torque tester is used to detect the inner hexagon torque of the outer connecting end to determine whether all indexes meet the industry standards and design requirements, if all meet the requirements, it is determined to be a qualified product, if any one is unqualified, it is determined to be an unqualified product, and the rework or scrap treatment is performed.

2. A manufacturing process of a piston rod for a passenger vehicle shock absorber according to claim 1, characterized in that, In the S3, the ratio of the forging temperature to the phase transition temperature of the titanium alloy base material is 0.8-0.9:1, and the ratio of the forging pressure to the yield strength of the base material is 1.2-1.5:

1.

3. A manufacturing process of a piston rod for a passenger vehicle shock absorber according to claim 1, characterized in that, In the S5, the quenching temperature Ta and the tempering temperature Tb are adjusted by a dynamic compensation model: when the furnace pressure < a preset threshold P1, Ta is adjusted up by 5-10 DEG C and Tb is adjusted down by 5-8 DEG C; when the furnace pressure > P1, Ta is adjusted down by 5-10 DEG C and Tb is adjusted up by 5-8 DEG C, and the temperature curve is monitored again until it is stable after compensation.

4. The manufacturing process of a piston rod for a passenger vehicle shock absorber according to claim 1, characterized in that, The control method in the S4 includes: setting a temperature detection module, a pressure detection module, a cutting parameter acquisition module and a tool wear detection module on the machining equipment, the temperature detection module monitors the processing area temperature T in real time, the pressure detection module monitors the cutting force F in the cutting process in real time, the cutting parameter acquisition module acquires the cutting speed V and the cutting depth A, and the tool wear detection module detects the wear amount W of the tool; presetting a temperature danger threshold T1, a temperature warning threshold T2, and T2 T1, a cutting force standard range [Fmin, Fmax], and a maximum allowable tool wear amount Wmax; when T>T1, the machining is immediately stopped and an alarm signal is sent out; when T2 T1, a cutting force standard range [Fmin, Fmax], and a maximum allowable tool wear amount Wmax; when T>T1, the machining is immediately stopped and an alarm signal is sent out; when T2 T1, a cutting force standard range [Fmin, Fmax], and a maximum allowable tool wear amount Wmax; when T>T1, the machining is immediately stopped and an alarm signal is sent out; when T2 T1, a cutting force standard range [Fmin, Fmax], and a maximum allowable tool wear amount Wmax; when T>T1, the machining is immediately stopped and an alarm signal is sent out; when T2 T1, a cutting force standard range [Fmin, Fmax], and a maximum allowable tool wear amount Wmax; when T>T1, the machining is immediately stopped and an alarm signal is sent out; when T2 T1, a cutting force standard range [Fmin, Fmax], and a maximum allowable tool wear amount Wmax; when T>T1, the machining is immediately stopped and an alarm signal is sent out; when T2 5. The manufacturing process of a piston rod for a passenger vehicle shock absorber according to claim 1, characterized in that, The control method in the S7 includes: setting a plating layer thickness detection module, a micro-crack counting module, a hardness detection module, an adhesion detection module and a defect detection module; first, measuring the plating layer thickness d by the plating layer thickness detection module, presetting the standard thickness range [0.015, 0.025], if adjusting the chromium plating current density and the chromium plating time, re-measuring after adjustment, until d∈[0.015, 0.025]; when d∈[0.015, 0.025], detecting the number of micro-cracks n in unit length by the micro-crack counting module, presetting the standard number n0=400 strips / cm, allowing a deviation of ±5%, if adjusting the cooling speed after chromium plating and the stress release process, re-detecting after adjustment, until n∈[n0×95%, n0×105%]; then detecting the plating layer hardness HV by the hardness detection module, presetting the standard hardness range [800, 1200], if returning to adjust the chromium plating process parameters and re-performing the chromium plating treatment; when n and HV both meet the requirements, performing the cross-hatch test and the thermal shock test by the adhesion detection module, observing whether the plating layer falls off by using a magnifying glass after the cross-hatch test, performing the thermal shock test by circulating the piston rod in the range of -40℃ to 120℃ for 5 times, each time for 30 min, detecting whether the plating layer falls off after the test; at the same time, detecting whether there are small spots and damage defects on the surface of the plating layer by using the industrial camera and the image processing technology, setting a defect area threshold S0, if the defect area S after image processing is S≥S0, determining that it is unqualified and re-plating; if there is no falling off in the adhesion detection and S<S0, determining that the plating layer is qualified; substituting d, n, HV, the adhesion detection result and S into the preset comprehensive score formula: K=0.3×(d / d0)+0.25×(n / n0)+0.2×(HV / HV0)+0.15×A+0.1×(1-S / S0), wherein d0 is the standard thickness intermediate value, HV0 is the standard hardness intermediate value, A is the adhesion detection coefficient, A=1 when there is no falling off and A=0 when there is falling off, calculating the comprehensive score K; if K≥0.9, determining that the chromium plating and micro-crack treatment are qualified and entering S8; if 0.8≤K<0.9, re-detecting K after repairing the plating layer, if K≥0.9 after repairing, entering S8, if K<0.9 after repairing, re-plating; if K<0.8, directly re-plating.

6. A manufacturing process of a piston rod for a passenger vehicle shock absorber according to claim 1, characterized by, In the S2, when the structural topology optimization design is performed, the ratio of the curvature radius of the streamline section to the diameter of the piston rod is 0.3-0.4:1, and the ratio of the height of the micro-rib to the wall thickness of the piston rod is 0.1-0.15:

1.

7. The manufacturing process of a piston rod for a passenger vehicle shock absorber according to claim 1, characterized in that, In the S9, the mechanical deburring uses a grinding wheel to grind, the rotating speed of the grinding wheel is 1000-1500 r / min, the grinding time is 5-10 min, the voltage of the electrochemical deburring is 10-20 V, and the treatment time is 3-8 min, after the deburring, the surface of the piston rod is observed by using a magnifying glass to ensure that there is no burr, no sharp edge, and the surface roughness Ra is ≤0.8 μm.

8. The manufacturing process of a piston rod for a passenger vehicle shock absorber according to claim 1, characterized in that, In the S10, the tensile speed of the tensile test is 2-5 mm / min, when the tensile strength of the piston rod >= 1000 MPa, the yield strength >= 800 MPa, and the elongation rate >= 10%, it is determined that the mechanical properties are qualified; when the inner hexagon torque of the outer connecting end is detected, the torque tester is used to gradually apply the torque, when the torque value is stable and greater than 70 N / m, it is determined that the torque is qualified, and all detection items are qualified before the product can be shipped.

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