Analysis of Screw Fracture of Car Shock Absorber

Analysis of Screw Fractures in Automobile Process and Material Car Shock Absorber Ren Xueliang, Kang Xiang, Dong Kefa Shanxi Aluminum Plant Equipment and Energy Department, Shanxi Hejin 043300 Metallographic Fracture Analysis. As a result, the screw fracture is due to the hardness being lower than the design requirements. It is recommended that the manufacturer strictly implement the heat treatment process, and the tempering temperature is controlled at 500, 笥 shaking T诎沧 concave 跽衿髀荻な, lemon, quality , 馐郑, ü, 匝檠≡袷实钡牧, 刂 ,, 琅 琅 琅 琅 蟆, 蟆, the Alto car travel more than 100,000 kilometers need to be overhauled, during the overhaul process, the assembly of the damper, in the mechanical force Under the action of the screw, the screw is pressed into the damper, but during the tightening process with the torque wrench, the screw is twisted, then replaced and then twisted, and the fracture surface is located at the 23rd buckle of the root of the thread. The technical management department tested and compared the two products due to the break and the purchase of new screws.

1 test analysis The car damper positioning screw material is 40 steel, the treatment process is tempered surface galvanized, the design hardness is 12836.

1.1 Chemical composition analysis The chemical composition of the screw was analyzed by the carbon-sulfur combination tester produced by Like Division of the United States and the radiation spectrometer of Siemens, and compared with the standard value of 40Cr steel. The analysis result 1 As can be seen from the data values ​​in 1, the chemical composition of the fractured screw meets the requirements of 40 steel.

40. Determination of the chemical composition of the steel screw 1.2 Hardness analysis For the convenience of analysis, the hardness of the broken screw and the hardness of the newly purchased screw were measured. The results are as follows: The newly purchased screw is the result of the hardness analysis. The hardness value is significantly lower than the design requirements.

1.3 Metallographic analysis A section of the sample was taken from the fractured screw and the normal screw to prepare a metallographic sample, which was observed and analyzed under a metallographic microscope. 1 The fracture screw is slightly thicker than the normal screw.

The fractured screw was observed and analyzed by scanning electron microscopy. 3 is the low-fold shape of the section. From the above, most of the sections have been worked.

38 The automobile process and materials were severely scratched, and there were obvious scribes and extrusion blocks on the section, 4 pieces. This shows that after the screw is broken, the two sections have relative sliding. Due to the low hardness of the screw, the section is scratched and squeezed during the relative sliding process. 5 is the appearance of the fracture surface after the enlargement. It can be seen from 5 that the fracture mode of the screw is plastic fracture. The final fracture zone is fibrous, with a microscopic morphology of 6, which is a dimple-like shape with spherical inclusions in the dimple. 03 Analysis shows that the composition of the spherical inclusions is observed and analyzed on the galvanized layer of the screw surface. The coating is dense and uniform, and its morphology is 7.

2 Conclusion 401 steel quenching and tempering treatment has good comprehensive mechanical properties, good low temperature impact, and low notch sensitivity, suitable for manufacturing parts such as connecting rod shaft crankshaft connecting rod bolts and gears. After the steel is quenched by 840 ,, different tempering temperatures are used, and the hardness is only a ruler, and the strength is significantly different. 400 tempering 1 hardness this is 35, = 02.5 cubits, 3, if the tempering temperature is increased to 600 弋, the hardness is 23, only the hardness of the 823.2 control broken screw, indicating that the tempering temperature of the screw is biased High, the hardness of the screw after tempering is much lower than the hardness required by the design, and the corresponding tensile strength is much lower. The screw is low during the tightening process, and its strength is not enough. Under the same tightening torque, the screw is easily deformed and broken. When the two sections of the fracture move relative to each other, they also cause scratches and crushing of the block. The conclusion of the fracture analysis proves this.

Through the above tests and analysis, the following is summarized.

3. After replacing the new screw with the car's damping screw, there is no breakage, indicating that the original purchased parts are unqualified products.

1. Screw breakage is due to the design requirements of hardness lower than the design requirements. Strict heat treatment system, tempering temperature should be controlled at 4. When installing the car damper screw, it is recommended to use a digital torque wrench to select the appropriate torque value through the test. In case of excessive stress during tightening.

Responsible editor Liang Wen is connected to page 35. Because the production line has a variety of products, such as steel rings and other processes do not need to be pickled, so according to the different products, 6 cars and cars, there are two sets of different procedures, 4 in the dotted line The procedure of pickling is not performed.

With the gantry crane conveying method, the placement of each tank body does not have to be arranged in the order of the process, and adjustment can be made if necessary, so that the space utilization of the plant is more reasonable, and the entire production line is more compactly arranged. This also provides a newer mold 3 drying furnace design for the design of the coating line. The structure of the advanced drying furnace is a bridge furnace, which is beneficial to reduce heat loss.

The advantages of using the oven exhaust gas combustion mode are as follows.

8. Reducing the emission of harmful gases is conducive to environmental protection.

It reduces the amount of air discharged from the drying furnace and replenishes the air volume, while saving heat and electricity.

The frame painting line is an advanced coating line designed and installed by Jiangling. Since it was completed and put into production in April 2000, it has achieved great economic and social benefits.

1 Wu Zeyong, Lu Hongwei, Xiao Zexing. New Coating Pre-treatment Application Handbook Chengdu Science and Technology Press, 199810.

Responsible editor Liang Wen is connected to page 37. The brazing temperature and holding time of the sample drop contact are slightly insufficient.

2.6 Conclusion The early fall-off of the car basin-shaped electric horn contact is due to weld defects. Contact weld non-welding and porosity defects are related to pre-weld cleaning brazing processes and quality control standards.

3 Treatment measures 3. According to the technical conditions of the imported parts, it is proposed to modify the weld quality acceptance standard of the product, and the required weld thickness is not more than 0.35nlnl; the tensile strength is not less than (1) the pre-weld cleaning process and the quality of the post-weld contact are added as soon as possible. Inspection equipment; weld strength test shall also be carried out after welding process adjustment.

Adjust the brazing process temperature according to the modified weld technology requirements.

Responsible editor Xin Min 40 automotive technology and materials

Epoxy potting is a room temperature curing type, heating will accelerate the curing speed. After thoroughly mixing the A component and the B component at a ratio of 2:1 (weight ratio), the product is cured for a certain period of time to form a protection.