Welding is a process of joining materials by melting metal at high temperatures. Gas Tungsten Arc Welding (GTAW) is one of welding method to join metals. This welding process will affect the mechanical properties of a material. So, it is necessary to conduct a study on changes in mechanical properties that occur. This study aims to determine the mechanical properties of AISI 1045 medium carbon steel using the GTAW welding process with a current variation of 80 A and 100 A. The welding was used the AWS EWTh-1 tungsten electrode and ER70S-G filler wire. The type of connection was used a butt weld joint and a single V groove seam with an angle of 60o. The standard of ASTM E8 was used for the manufacture of tensile test specimens. The results of tensile testing with welding current of 80 A was obtained an average stress of 518.463021 N/mm2 and the strain of 19.55%. For welding with a current of 100 A, the average stress was 548.814727 N/mm2 and the strain of 26.44%. Based on the fracture that occurred in the specimen, the critical area for fracture was the Heat Affecting Zone (HAZ), which the area has undergone a phase change during the cooling process. The weld area of connection part in the welding process has higher strength than the HAZ area.

<p>Steel materials is widely used as a component of the gears, shafts and bearing that required several factors such as impact strength, , hardness , toughness, ductility and. Etc. The process tempering includes heating steel AISI 1045 at low temperatures 2000C and 3000C, maintained at a particular time and refrigerated, oil cooling oil, water and oil plus water (mix). The purpose of this research is to acknowledge the changing impact strength and hardness material resulting from the process of tempering so getting to specifications and standards impact strength. hardness of materials. <br />Impact strength highest cooling oil d = 19 mm temperature 2000C =14,43x104 joule / m2 and d = 19 mm temperature 3000C = 14,62x104 joule /m2 and cooling oil plus water (mix) d=2mm 2000C 11,23x104 joule / m2 and d = 25 mm temperature 3000C 12,96x104 joule / m2. In a cooling oil hardness highest d = 25 mm 3000C from the edge (Ra) 37,5 HRC and lowest d = 19 mm 2000C temperature from the edge (Ra) 18,5 HRC, water cooling hardness highest d = 25mm 3000C from the edge (Ra) 43 HRC and lowest temperature d=19 mm 2000C from the edge (Ra) 23 HRC and cooling plus water(mix) the highest hardnesst (Ra) d=19mm 2000C from the edge (Ra) 36,5 HRC and lowest d=25mm 3000c temperature from the edge (Ra) 16 HRC.<br />Impact strength by the cooling oil has value greater strength from cooling water and cooling oil plus water. The hardness of materials by the highest water cooler temperatures d=25 mm 300 0c from the edge 43HRC than media cooling oil and oil plus water. The impact strength highest with cooling oil and hardness highest with cooling water then the impact strength and hardness materials non uniform in any variation diameter.</p>

Baja AISI 1045 biasanya dipakai sebagai komponen automotif yang aplikasinya sering mengalami pembebanan, gesekan dan tekanan. Tujuan penelitian untuk pelunakan sehingga kekuatan Tarik, kekuatan Impak dan kekerasan menjadi lebih baik sehingga dilakukan proses full annealing quench oli dan air. Rata-rata kecepatan pendinginan adalah faktor menentukan kekerasan suatu material. Proses full annealing quench oli adanya pelunakan cukup baik yang menurunkan kekerasan dengan kekerasan tertinggi 3,5 HRC temperatur 8500C sedangkan quench air kekerasan tertinggi 43 HRC temperatur 8000C. Kekuatan impak quench oli tertinggi temperatur 7500C bernilai 10,95x104 Joule/m2 sedangkan quench air tertinggi temperatur 7500C bernilai 16,71x104 Joule/m2. Kekuatan ulur tertinggi pada suhu 8000C quench oli bernilai 949,02 N/mm2 sedangkan kekuatan ulur tertinggi pada suhu 7500C quench air bernilai 1683,23 N/mm2 tetapi material ini rapuh dibandingkan dengan quench oli yang mempunyai keliatan yang cukup baik.

Experiment is looking at the influence of dimensions, heat treatment temperature and cooling media effect linearly on hardness, tensile strength steel AISI 4140 so that the level comparison of the hardness of influence on the diameter variation (input effects the response). The Full Factorial Design of Experiment Method is used to assess the results of the hardness test in accordance with the testing hypothesis. Design of Experiment (DOE) has been widely used to determine design factors that significantly influence target responses and build empirical models that represent relationships between significant factors. Reviewing the literature revealed that the majority of researchers explored various DOE. Response Tempering heat treatment with Quenching Oil media, this study used AISI 4140 material with a diameter of 29 mm, 33 mm and 35 mm. Results AISI 4140 of commercial production by partial cutting are then taken for hardness testing. The Full Factorial Design of Experiment Method is used to assess the results of the hardness test in accordance with the hypothesis according to the analysis of variance(Anova). The response of the hardness test data input in the 30 0 & 90 0 direction is not influenced by the AISI 4140 material dimensions and the direction of the test surface data retrieval.