A valve spring steel wire full supply chain path verification method

Abstract

The application discloses a valve spring steel wire full supply chain path verification method and relates to the technical field of automobile engine part detection. The method moves the verification endpoint to the steel wire raw material stage, selects 9254V material spring steel wire, applies bending normal stress by using a rotary bending testing machine to perform preposition dynamic testing, then takes 0.45-0.55 times of tensile strength as an initial stress limiting interval, and uses a ladder lifting method to perform 2000-2500 million times of alternating stress loading testing, calculates B 50 median fatigue limit by using an extreme likelihood estimation algorithm and other algorithms after the testing, and controls double micro-morphology of depth (0-300 microns) and size (maximum size is less than or equal to 60 microns) of crack inclusions, and the qualified raw material enters a spring finished product bench fatigue (2300-2800 million times) and market tracking verification stage. By high-frequency dynamic testing algorithm and high coordination of subsurface micro-control standards, the application cuts off potential high-cycle fatigue failure hidden dangers at the source, and ensures very low post-sale failure rate of the valve spring assembly.

Description

Technical Field

[0001] This invention relates to the field of quality control and testing technology for automotive engine parts, specifically to a verification method for the entire supply chain path of valve spring steel wire. Background Technology

[0002] Valve springs are core dynamic stress-bearing components in passenger car engines, and their reliability directly affects the engine's operational stability and lifespan. Currently, the domestic market for valve spring raw materials for passenger car engines mainly relies on imports, but some domestic steel mills and spring manufacturers have begun to explore the possibility of domestically produced materials.

[0003] However, existing conventional verification systems suffer from significant "insufficient verification" defects. Traditional raw material testing is time-consuming and cannot establish an accurate mathematical mapping relationship with the lifespan of finished products under extremely high stress. While bench testing relying on the finished product spring stage is intuitive, it often fails to accurately and quantitatively reflect the impact of microscopic defects in the underlying material (especially subsurface micro-inclusions). These subsurface defects are difficult to expose in conventional finished product testing, but when the engine is under extreme operating conditions for a long time, they can cause significant stress concentration, becoming the initiation source of ultra-high cycle fatigue cracks. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a verification method for the entire supply chain of valve spring steel wire, which aims to establish an accurate mathematical mapping from microscopic defect detection to the macroscopic life of finished products. By introducing a collaborative algorithm of stepped stress and microscopic control in the initial screening stage of raw materials, the potential for high-cycle fatigue can be eliminated at the source.

[0005] To address the aforementioned technical problems, this invention provides a supply chain verification method that includes "steel wire raw material screening - finished product bench verification - market data tracking".

[0006] A method for verifying the entire supply chain path of valve spring steel wire includes the following steps: S1 Pre-testing dynamic test of steel wire samples: Samples of valve spring steel wire from the batch to be verified were taken. The valve spring steel wire was made of 9254V material, with a diameter of 3.0 ~ 4.0 mm and a tensile strength rating of 1800 ~ 2100 MPa. A high-cycle fatigue test was performed on a single steel wire sample using a rotary bending tester. The loading method was bending normal stress loading, and the equivalent stress conversion criterion was used to correlate it with the actual torsional shear stress of the spring. The number of test cycles for a single sample was set to 20 million ~ 25 million cycles. S2 Step-by-Step Dynamic Stress Adjustment: The initial test stress σ0 of the first test specimen is set to satisfy the relationship σ0=k × σ b , where σ bThe tensile strength of the steel wire is given by the coefficient k, which ranges from 0.45 to 0.55. In subsequent tests, if the previous sample breaks, the test stress of the current sample is reduced by a preset value; if the previous sample does not break, the test stress of the current sample is increased by the preset value. S3 Dual Control of Macroscopic Statistics and Microscopic Morphology: After testing all samples, the B-value of the batch of samples is calculated based on the test data using the maximum likelihood estimation method or the Dixon-Mood formula. 50 Median fatigue limit stress; when the calculated B 50 If the median fatigue limit stress is greater than or equal to the target reference stress, and the proportion of samples fractured due to inclusions is ≤ 20% of the total number of fractured samples, a microscopic scan is performed on the fracture surface caused by inclusions. If the inclusions causing the fracture are located within a depth range of 0 ~ 300 μm below the surface of the steel wire, and the maximum size of the inclusions is ≤ 60 μm and the average size is ≤ 40 μm, then the batch of steel wire raw materials is deemed to be qualified. S4 Fatigue verification of finished springs: The batch of steel wires that passed the verification in step S3 are used to prepare valve springs, and bench fatigue tests are conducted on the valve springs; the average stress of the bench fatigue test is 600 ~ 650 MPa, and the stress amplitude is 380 ~ 430 MPa.

[0007] Furthermore, in step S1, before the valve spring steel wire is drawn and formed, the wire rod undergoes a surface peeling treatment to remove the outer layer of material of 200~400 μm.

[0008] Furthermore, in step S1, the number of steel wire samples to be verified is 25 to 35, and the length of a single steel wire sample is 60 to 120 cm.

[0009] Furthermore, in step S2, the preset amplitude is set according to the standard deviation σ of the prior test estimate, so that it meets the range of 0.5σ to 1.5σ.

[0010] Furthermore, in step S3, the definition criterion for the depth of the inclusion is the vertical distance from the outer surface of the steel wire to the core of the inclusion; the size of the inclusion is obtained by measuring the maximum radial length of the inclusion on the fracture surface.

[0011] Furthermore, the microstructure control standard further preferred in step S3 is as follows: the inclusions that cause fracture are located at a depth of 0 to 150 μm below the surface of the steel wire, and the maximum size of the inclusions is ≤ 48 μm and the average size is ≤ 32 μm.

[0012] Furthermore, the dimensional parameters of the valve spring in step S4 are: inner diameter 11 ~ 18 mm, pitch 5.0 ~ 10.0 mm, and number of turns 4 ~ 10.

[0013] Furthermore, in the bench fatigue test of step S4, the testing equipment uses an eccentric wheel or servo mechanism to cause relative displacement vibration at both ends of the spring for loading; the total test frequency is 23 million to 28 million times, and the pass / fail criterion is: the spring does not break or fail after the test, and the spring force reduction at the fully open valve height does not exceed 5%.

[0014] Furthermore, the verification method for the entire supply chain path of the valve spring steel wire mentioned above also includes the following step: S5 Market Installation Tracking Verification: The corresponding batch of valve springs that passed the verification in step S4 are installed in the engine. The qualification criterion is: within 12 months after sale, the valve spring breakage failure rate is less than 1 × 10 -6 .

[0015] In the steel wire raw material screening stage, the raw material was identified as 9254V high-strength steel. A rotary bending tester was introduced to apply bending normal stress. The initial test stress of the first test sample was set to 0.45~0.55 times the tensile strength. A step-up / step-down method based on a preset amplitude set according to the prior standard deviation was used to perform 20-25 million cycles. Subsequently, the maximum likelihood estimation method or the Dixon-Mood algorithm was introduced to obtain B. 50 The median fatigue limit stress was determined, and the fracture origin was strictly controlled with a depth of 0 ~ 300 μm (high stress sensitive zone) and a maximum size of 60 μm.

[0016] Compared with the prior art, the present invention has the following advantages: Improved stress sensitivity and hazard detection rate: By introducing a 0.5×σ-based method at the steel wire raw material stage. b The initial setting and preset amplitude step dynamic algorithm, combined with maximum likelihood estimation or Dixon-Mood algorithm, yields B. 50 The median fatigue limit accurately captures the true fatigue limit of the material. This dynamic test fully stimulates the stress concentration effect of subsurface micro-defects, enabling hidden brittle inclusion defects to emerge more quickly.

[0017] Reduced Trial and Error and Manufacturing Costs: Overcoming the limitations of traditional methods that heavily rely on the lagging testing of finished springs, a stringent quantitative standard for judging microscopic failure tolerance has been established (i.e., within the high-stress-sensitive 0~300 μm depth layer, the average size ≤ 40 μm, and the maximum size ≤ 60 μm). This standard, combined with pre-stripping treatment of wire rods, can accurately intercept inferior steel wires with inherent defects before spring winding, significantly reducing the scrap rate of substandard raw materials flowing into subsequent processing stages.

[0018] Ensuring ultra-high cycle fatigue life and extremely low after-sales failure rate: By intercepting at the source, the geometric dimensions of critical inclusions that cause high-cycle fatigue crack initiation are strictly controlled within a safe threshold. This objectively ensures that the manufactured valve springs can withstand 23-28 million ultra-high cycle fatigue tests under an average stress of 600-650 MPa without fracture. Ultimately, this keeps the market after-sales failure rate of the assembled engine extremely low at 1 × 10⁻⁶. -6 the following. Detailed Implementation

[0019] The present invention will be further illustrated by way of embodiments below, but the present invention is not limited to the scope of the embodiments described herein.

[0020] A method for verifying the entire supply chain path of valve spring steel wire includes the following steps: S1 Pre-testing dynamic test of steel wire samples: Samples of valve spring steel wire from the batch to be verified were taken. The valve spring steel wire was made of 9254V material, with a diameter of 3.0 ~ 4.0 mm and a tensile strength rating of 1800 ~ 2100 MPa. A high-cycle fatigue test was performed on a single steel wire sample using a rotary bending tester. The loading method was bending normal stress loading, and the equivalent stress conversion criterion was used to correlate it with the actual torsional shear stress of the spring. The number of test cycles for a single sample was set to 20 million ~ 25 million cycles. S2 Step-by-Step Dynamic Stress Adjustment: The initial test stress σ0 of the first test specimen is set to satisfy the relationship σ0=k × σ b , where σ b The tensile strength of the steel wire is given by the coefficient k, which ranges from 0.45 to 0.55. In subsequent tests, if the previous sample breaks, the test stress of the current sample is reduced by a preset value; if the previous sample does not break, the test stress of the current sample is increased by the preset value. S3 Dual Control of Macroscopic Statistics and Microscopic Morphology: After testing all samples, the B-value of the batch of samples is calculated based on the test data using the maximum likelihood estimation method or the Dixon-Mood formula. 50 Median fatigue limit stress; when the calculated B50 If the median fatigue limit stress is greater than or equal to the target reference stress, and the proportion of samples fractured due to inclusions is ≤ 20% of the total number of fractured samples, a microscopic scan is performed on the fracture surface caused by inclusions. If the inclusions causing the fracture are located within a depth range of 0 ~ 300 μm below the surface of the steel wire, and the maximum size of the inclusions is ≤ 60 μm and the average size is ≤ 40 μm, then the batch of steel wire raw materials is deemed to be qualified. S4 Fatigue verification of finished springs: The batch of steel wires that passed the verification in step S3 are used to prepare valve springs, and bench fatigue tests are conducted on the valve springs; the average stress of the bench fatigue test is 600 ~ 650 MPa, and the stress amplitude is 380 ~ 430 MPa.

[0021] Tests and Preconditions Disclosure Raw material disclosure: The wire rod raw material is 9254V, with a diameter of 5.0 ~ 7.0 mm. The valve spring steel wire prepared after drawing has a diameter of 3.0 ~ 4.0 mm, and its tensile strength σ... b The calibrated range is 1800 ~ 2100 MPa.

[0022] The specifications and fatigue verification conditions for the finished valve springs are disclosed: the dimensions of the prepared valve springs must meet the following requirements: inner diameter 11 ~ 18 mm, pitch 5.0 ~ 10.0 mm, number of coils 4 ~ 10. The average stress in bench testing should be controlled between 600 ~ 650 MPa, and the stress amplitude between 380 ~ 430 MPa.

[0023] The testing methods and instruments are disclosed: a CNC rotary bending tester is used, the loading method is bending normal stress loading, and the stress is converted into actual torsional shear stress for evaluation through the equivalent stress conversion criterion.

[0024] Example 1 S1 steel wire sample pre-test dynamic test: 9254V wire rod was selected, and after surface peeling treatment (removing the outer layer of 300 μm), it was drawn into valve spring steel wire with a diameter of 3.5 mm. The tensile strength σ was measured. b The stress was 1940 MPa. Thirty samples, each 80 cm long, were placed on a rotary bending tester and subjected to bending normal stress loading. The number of cycles was set to 23 million.

[0025] S2 Step-by-Step Dynamic Stress Adjustment: The initial test stress coefficient of the first test sample is set to k=0.50, i.e., σ0= 0.50 × 1940 = 970 MPa. The preset amplitude is 25 MPa, which is set according to the prior test, and the test stress is dynamically adjusted according to whether the previous sample breaks, using a step-by-step method.

[0026] The distribution of the test sequences for the 30 samples is shown in the table below:

[0027] S3 Dual Control of Macroscopic Statistics and Microscopic Morphology: Based on the Dixon-Mood Formula Calculate, where X0 = 970 MPa, d = 25 MPa, effective fracture number N = 14, weighted value 0×3+1×7+2×4=15, substituting into the equation, we get the median fatigue limit μ=970+25×(15 / 14-0.5)≈984.3MPa, rounded down to B. 50 The median fatigue limit stress was 985 MPa (greater than the set target reference stress of 950 MPa), meeting the standard. Macroscopic statistics revealed that inclusions caused fractures in 14.3% of the total fractures (i.e., 2 out of 14 fractured samples were induced by inclusions). SEM scanning showed that the fracture-inducing inclusions were located at a depth of approximately 150 μm below the surface, with a maximum size of 48 μm and an average size of 32 μm. Therefore, this batch of steel wire raw materials was deemed to have passed the verification.

[0028] S4 Finished Spring Fatigue Verification: The qualified batch of steel wire was used to prepare valve springs (inner diameter 17 mm, pitch 5.5 mm, 9 coils) and subjected to 23-28 million bench tests on testing equipment (average stress 630 MPa, stress amplitude 410 MPa). No fracture failure occurred after the test, and the spring force reduction at the fully open valve height was only 1.8%.

[0029] S5 Market Installation Tracking Verification: After assembling the corresponding batch of valve springs into engines, market data tracking within 12 months of after-sales service confirmed that the breakage failure rate was consistently less than 1 × 10⁻⁶. -6 .

[0030] Example 2 S1 steel wire sample pre-test dynamic test: 9254V wire rod was selected, and after surface peeling treatment (removing the outer layer of 200 μm), it was drawn into valve spring steel wire with a diameter of 4.0 mm, and the tensile strength σ was measured. b The pressure was 1800 MPa. 25 samples, each 60 cm in length, were cut and tested 20 million times.

[0031] S2 Step-by-step dynamic stress adjustment: Set the lower limit of the initial test stress coefficient k=0.45, that is, σ0=0.45 × 1800 = 810 MPa, and set the preset amplitude to 20 MPa. Perform dynamic stress loading according to the step method.

[0032] The distribution of the test sequences for the 25 samples is shown in the table below:

[0033] S3 Dual Control of Macroscopic Statistics and Microscopic Morphology: Following the technical method of Example 1, where X0=810 MPa, d=20 MPa, effective number of sample fractures N=12, weighted value 0×0+1×0+2×7+3×3+4×2=31, substituting this into the equation, we get the median fatigue limit μ=810+20×(31 / 12-0.5)≈851.6MPa, rounded down to B. 50 The median fatigue limit stress was 852 MPa (greater than the lower limit target reference stress of 850 MPa), meeting the standard. Macroscopic statistics revealed that inclusions caused fractures in 16.7% of the total fractures (i.e., 2 out of 12 fractured samples were induced by inclusions). SEM scanning showed that the fracture-inducing inclusions were located at a depth of approximately 100 μm, with a maximum size of 55 μm and an average size of 38 μm, thus determining that this batch of raw materials passed the verification.

[0034] S4 Finished Spring Fatigue Verification: Steel wire was formed into a valve spring (dimensions at the lower limit: inner diameter 16 mm, pitch 5.0 mm, number of coils 8). A bench fatigue test of 23 million cycles was conducted, with an average stress of 600 MPa and a stress amplitude of 380 MPa. No fracture failure occurred after the test, and the spring force decreased by 1.5%.

[0035] S5 Market Installation Tracking Verification: When the corresponding batch of valve springs is installed in the engine, the breakage failure rate within 12 months after sale is less than 1 × 10⁻⁶. -6 .

[0036] Example 3 S1 steel wire sample pre-test dynamic test: 9254V wire rod was selected, and after surface peeling treatment (removing the outer layer of 400 μm), it was drawn into valve spring steel wire with a diameter of 3.0 mm, and the tensile strength σ was measured. b The pressure was 2100 MPa. 35 samples, each 120 cm in length, were cut and tested 25 million times.

[0037] S2 Step-by-step dynamic stress adjustment: Set the initial test stress coefficient of the first piece to k=0.55, that is, σ0= 0.55 ×2100 = 1155 MPa, and set the preset amplitude to 30 MPa. Perform dynamic stress loading according to the step method.

[0038] The distribution of the test sequences for the 35 samples is shown in the table below:

[0039] S3 Dual Control of Macroscopic Statistics and Microscopic Morphology: Following the calculation method of Example 1, where X0=1155 MPa, d=30 MPa, effective number of sample breaks N=17, weighted value 0×2+1×10+2×4+3×1=21, substituting into the equation, we get the median fatigue limit μ=1155+30×(21 / 17-0.5)≈1177.1MPa, which is B. 50 The median fatigue limit stress was 1177 MPa (greater than the target reference stress of 1150 MPa), meeting the standard; the inclusion fracture rate was 17.6% (3 out of 17 fractured samples). SEM scanning showed that the fracture-causing inclusions were located at a depth of approximately 220 μm below the surface, with a maximum size of 58 μm and an average size of 35 μm, which was deemed acceptable.

[0040] S4 Finished Spring Fatigue Verification: Steel wire was formed into valve springs (sizes at the upper limit: inner diameter 18 mm, pitch 5.8 mm, number of coils 10). 28 million bench fatigue tests were conducted, with an average stress of 650 MPa and a stress amplitude of 430 MPa. No fracture failure occurred after the test, and the spring force decreased by 2.1%.

[0041] S5 Market Installation Tracking Verification: When the corresponding batch of valve springs is installed in the engine, the breakage failure rate within 12 months after sale is less than 1 × 10⁻⁶. -6 .

[0042] Comparative Example 1 S1 steel wire sample pre-test dynamic test: 9254V wire rod was selected, and after surface peeling treatment (removing the outer layer of 300 μm), it was drawn into valve spring steel wire with a diameter of 3.5 mm. The tensile strength σ was measured. b The pressure was 1900 MPa. A sample of 30 roots, each 80 cm in length, was taken and tested for 22 million cycles.

[0043] S2 Step-type dynamic stress adjustment: Using an intermediate coefficient k=0.50, the initial test stress σ0= 0.50 ×1900 = 950 MPa, and the preset amplitude set to 25 MPa, dynamic adjustment is performed.

[0044] The distribution of the test sequences for the 30 samples is shown in the table below:

[0045] S3 Dual Control of Macroscopic Statistics and Microscopic Morphology: Following the calculation method of Example 1, where X0=950 MPa, d=25 MPa, effective number of sample breaks N=14, weighted value 0×3+1×8+2×3=14, substituting into the formula μ=950+25×(14 / 14-0.5)=962.5MPa, that is, B 50 The median fatigue limit stress was 963 MPa (greater than the target reference stress of 950 MPa), and the macroscopic stress indicators met the standards. The inclusion fracture rate was 21.4% (3 out of 14 fracture samples), but microscopic features were found to exceed the standards: SEM scanning showed that the depth of the fracture-inducing inclusions was 180 μm, but the maximum size reached 85 μm. Therefore, this batch of raw materials was deemed unqualified.

[0046] S4 Finished Spring Fatigue Verification: The substandard batch of steel wire was forcibly manufactured into valve springs and subjected to bench testing (average stress 630 MPa, stress amplitude 410 MPa). Early fracture failure occurred after 11 million cycles.

[0047] Summary and comparative analysis of experimental results: Comparing the experimental data of Comparative Example 1 with Examples 1-3 reveals that, while maintaining consistent wire rod surface processing, if the secondary surface of the steel wire contains microscopic inclusions exceeding the size limits of this invention (maximum size greater than 60 μm), the valve springs prepared from them experience early high-cycle fatigue fracture failure during finished product bench testing. Conversely, the results of Examples 1-3 demonstrate that within the parameter range defined by this invention (initial test stress coefficient 0.45-0.55, test cycle count 20-25 million cycles), this pre-test dynamic verification method can stably and fully expose secondary surface defects. Qualified raw materials selected through this mechanism, after being molded into finished valve springs at various dimensional extremes, can successfully pass ultra-high-cycle fatigue tests under extremely high average stress, objectively verifying the technical effectiveness of this invention in eliminating potential failures at the source and ensuring an extremely low market failure rate.

[0048] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for verifying the entire supply chain path of valve spring steel wire, characterized in that, Includes the following steps: S1 Pre-testing dynamic test of steel wire samples: Samples of valve spring steel wire from the batch to be verified were taken. The valve spring steel wire was made of 9254V material, with a diameter of 3.0 ~ 4.0 mm and a tensile strength rating of 1800 ~ 2100 MPa. A high-cycle fatigue test was performed on a single steel wire sample using a rotary bending tester. The loading method was bending normal stress loading, and the equivalent stress conversion criterion was used to correlate it with the actual torsional shear stress of the spring. The number of test cycles for a single sample was set to 20 million ~ 25 million cycles. S2 Stepped Stress Dynamic Adjustment: The initial test stress σ0 of the first test sample is set to satisfy the relationship σ0 = k × σ b , where σ b The tensile strength of the steel wire is given by the coefficient k, which ranges from 0.45 to 0.

55. In subsequent tests, if the previous sample breaks, the test stress of the current sample is reduced by a preset value; if the previous sample does not break, the test stress of the current sample is increased by the preset value. S3 Dual Control of Macroscopic Statistics and Microscopic Morphology: After testing all samples, the B-value of the batch of samples is calculated based on the test data using the maximum likelihood estimation method or the Dixon-Mood formula. 50 Median fatigue limit stress; when the calculated B 50 If the median fatigue limit stress is greater than or equal to the target reference stress, and the proportion of samples fractured due to inclusions is ≤ 20% of the total number of fractured samples, a microscopic scan is performed on the fracture surface caused by inclusions. If the inclusions causing the fracture are located within a depth range of 0 ~ 300 μm below the surface of the steel wire, and the maximum size of the inclusions is ≤ 60 μm and the average size is ≤ 40 μm, then the batch of steel wire raw materials is deemed to be qualified. S4 Fatigue verification of finished springs: The batch of steel wires that passed the verification in step S3 are used to prepare valve springs, and bench fatigue tests are conducted on the valve springs; the average stress of the bench fatigue test is 600 ~ 650 MPa, and the stress amplitude is 380 ~ 430 MPa.

2. The verification method for the entire supply chain path of valve spring steel wire according to claim 1, characterized in that, Before being drawn into shape, the valve spring steel wire in step S1 undergoes a surface peeling process to remove the outer 200~400 μm of material.

3. The verification method for the entire supply chain path of valve spring steel wire according to claim 1, characterized in that, In step S1, the number of steel wire samples to be verified is 25 to 35, and the length of a single steel wire sample is 60 to 120 cm.

4. The verification method for the entire supply chain path of valve spring steel wire according to claim 1, characterized in that, In step S2, the preset amplitude is set according to the standard deviation σ of the prior test estimate, so that it meets the range of 0.5σ to 1.5σ.

5. The verification method for the entire supply chain path of valve spring steel wire according to claim 1, characterized in that, In step S3, the definition criterion for the depth of the inclusion is the vertical distance from the outer surface of the steel wire to the core of the inclusion; the size of the inclusion is obtained by measuring the maximum radial length of the inclusion on the fracture surface.

6. The verification method for the entire supply chain path of valve spring steel wire according to claim 1, characterized in that, The further preferred microstructure control standard in step S3 is as follows: the inclusions that cause fracture are located within a depth range of 0 to 150 μm below the surface of the steel wire, and the maximum size of the inclusions is ≤ 48 μm and the average size is ≤ 32 μm.

7. The verification method for the entire supply chain path of valve spring steel wire according to claim 1, characterized in that, In step S4, the valve spring dimensions are: inner diameter 11 ~ 18 mm, pitch 5.0 ~ 10.0 mm, and number of turns 4 ~ 10.

8. The verification method for the entire supply chain path of valve spring steel wire according to claim 1, characterized in that, In the bench fatigue test in step S4, the testing equipment loads the spring by causing relative displacement vibration at both ends through an eccentric wheel or servo mechanism; the total test frequency is 23-28 million cycles, and the pass / fail criterion is: the spring does not break or fail after the test, and the spring force reduction at the fully open valve height does not exceed 5%.

9. The verification method for the entire supply chain path of valve spring steel wire according to claim 1, characterized in that, The process also includes step S5: Market Installation Tracking Verification. This involves assembling the corresponding batch of valve springs that passed verification in step S4 into the engine. The pass / fail criterion is: within 12 months of sale, the valve spring breakage failure rate is less than 1 × 10⁻⁶. -6 .

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