| Summary: | 碩士 === 國立高雄應用科技大學 === 模具系碩士在職專班 === 103 === ABSTRACT
This research theme aim of investigation for the hydrogen embrittlement of low carbon screws with case harden after electroplating process. The experimental samples are performed completely screw heading,threading, case harden and electroplating by SAE C1022 carbon steel. To analyze and investigate the hydrogen embrittlement result from three different kinds screw samples, the first one is without case harden, the second one has case harden and its core hardness is above 400HV and the third one also has case harden but its core hardness is under 390HV. These three different heat treatment conditions and then after electroplating process samples for analysis and discussion of hydrogen embrittlement by way of analyzing the mechanical performance, hardness test, hydrogen embrittlement test and micro- photograph.
Mechanical property testing and metallographic observations, the case depth is deeper and core hardness is higher from Martensitic microstructure that gets more risk of hydrogen embrittlement fracture than the screws without case hardened compares with the value of torque and Hydrogen embrittlement locking value from ferrite, spheroidized cementite and martensitic microstructure. According to metallographic, the microstructure of
Ferrite and Spheroidized Cementite of screw without case hardened, it does not have hydrogen embrittlement fracture after any electrolytic plating process. Test samples hydrogen content of hydrogen embrittlement fracture is also higher than those samples do not get break. The hydrogen molecule is existed in the manufacturing process.
This research results recommend the screws must have baking process after electroplating even the screws meet the required dimensions and specification of mechanical property. To choose the appropriate chemical composition of the material to avoid the invasion of hydrogen molecules and in addition to watching the hydrogen time but also pay special attention to the thickness of the screw product lay out, make the product even withstand temperatures than hydrogen to avoid hydrogen embrittlement fracture screw product.
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