碩士 / 大葉大學 / 醫療器材設計與材料碩士學位學程 / 105 / In the 1980s, the US developed a new generation of vessel steel named HSLA series, which belonged to precipitation hardening steels of High-Strength-Low-Alloy Steel characteristics. In this study, the microstructure and hardness of HSLA-80 standard quenching and tempering heat treatment process and the microstructure and hardness of "rolling + quenching + aging" (DQT) were compared, and the mechanical properties of DQT process were further studied. The results showed that the microstructure under DQT was more detailed than that under the standard quenching and tempering process, and the hardness value was also increased by about 15 HV scale. In the test of the mechanical properties of raw materials (DQ) and DQT, the DQT impact value was better than DQ when the operating temperature was lower than room temperature (25 ℃) and the DQT impact value reached to the highest value at room temperature. However, when the temperature reached 50 ℃, the DQT impact would drop dramatically due to the appearance of a large number of quasi-cleavage. On the contrary, DQ had a large number of dimple appearance, resulting in an increasing in impact toughness by about 15% over DQT. The results of tensile test at room temperature and 50 ℃ showed that the yield strength and tensile strength of DQT were better than DQ, increasing by about 18% and 16% respectively. According to the results of the comprehensive analysis, we can infer a conclusion that the mechanical properties of DQT are better than those of the raw material (DQ).
FCAW weldment research results show: weld organization for the ferrite; base material for the ferrite – bainite organization. The impact value of the weld is gradually increased with the increase of the operating temperature, and the highest value is 189 J/cm2 at 50 ℃.The impact value of the heat affected zone also has the same trend, but at room temperature (RT) has a significant increase, the impact value of about 188 J/cm2, compared to the weld temperature (RT) impact value increased by about 118%.The thermal impact zone has the same trend, but at room temperature (RT), the impact value is about 188 J/cm2, which is about 118% higher than that of the weld at room temperature (RT).And the tensile strength decreased slightly with the temperature, decreased by about 8%, the elongation did’t decline still maintain a certain degree of ductility.SEM observation of the microstructure of the fracture surface quasi-cleavage, with the operating temperature rise gradually into a dimple.Weldments at the operating temperature of 50 ℃ and room temperature are found in the precipitation ofε-Cu, the formation of precipitation to enhance the impact of enhanced.
Due to the first welding of the mechanical properties of the lower than the standard, follow-up to change the welding parameters for the second welding, according to the experimental results that the increase in welding times to reduce the amount of heat input per pass, the strength can be improved.
| Identifer | oai:union.ndltd.org:TW/105DYU00747009 |
| Date | January 2017 |
| Creators | Chia-Hung Liao, 廖家宏 |
| Contributors | Li, Yi-Kang, 李義剛 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 103 |
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