Study of Heat-treatment Distortion on Hexagonal head screw (M8×150) of medium carbon steel (SAE 1035SK)

• Main Authors: Zhi-Wei Wu, 吳志偉
• Other Authors: Yu-Sen Yang
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/9w4k6c

碩士 === 國立高雄第一科技大學 === 機械與自動化工程研究所 === 105 === This experiment mainly performed heat treatment on hexagon head screws (SAE 1035SK M8X150) made of medium carbon steel, and the heat treatment involved thermal refining. Before heat treatment, the screws were numbered, and a straightness tester was used to measure and record screw straightness before and after the heat treatment. The parameters for heat quenching and tempering the treatment included quenching temperature (850 °C, 870 °C, and 890 °C), input amount (840, 560, and 280 kg), speed of the quenching conveyor (55 min), quenching oil temperature (75 ± 5 °C), tempering temperature (490 °C), and speed of the tempering conveyor (70 min). After quenching and tempering, the effects of heat treatment on the straightness deformation of 35ACR 1/4X5-1/2 hexagonal head screws were explored. The experimental procedure was divided into four phases. In the first phase, the relationship between quenching placement direction and screw straightness was tested by using a straightness tester to analyze straightness changes before and after experiment. In the second phase, the relationship between quenching temperature and straightness was tested by using a Rockwell hardness tester to analyze hardness changes before and after experiment. In the third phase, actual samples were tested. The samples were randomly distributed on the mesh belt of the quenching conveyor for testing, and the straightness tester was adopted to analyze straightness changes before and after experiment. In the fourth phase, the metallographic structure of the samples was observed. After cutting, polishing, and embedding the experimental samples, this study used an optical microscope to observe if their metallographic structure exhibit a normal quenching and tempering structure. The experimental results indicated that for the test on placement direction, the samples’ levels of straightness deformation were lower when placed parallel to the mesh belt than when placed perpendicular to the belt. The test on temperature differences confirmed that the furnace temperature was evenly distributed, and thus the samples and experimental data would not be affected by temperature differences during the test. Moreover, the extent of straightness deformation increased with temperature and input amount. The metallographic analysis determined that the samples exhibited a normal quenching and tempering structure. Keywords: level of deformation, straightness, SAE 1035SK, heat treatment