• The Journal of Korean Academy of Prosthodontics
• /
• v.19 no.1
• /
• pp.55-60
• /
• 1981

Some physical properties of Ni-Cr based alloy for porcelain veneering were compared after repeated casting without the addition of any new alloy. The specimen were cast in a centrifugal caster with an oxygen-propane torch at optimum temperature. The obtained results were as follows: 1. The yield strength and hardness of the second generation were no significant differences compared with first generation but the yield strength and hardness of the third generation slightly decrased. 2. The ultimate tensile strength and elongation appeared to decrease slightly in second, third generations. 3. The tensile fractured facets of the first generation specimen were normal in all specimen, but in the second generation there were six tensile specimen out of ten, in the third there were four tensile specimen out of ten.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.4
• /
• pp.407-412
• /
• 2010

The objective of this study is the estimation of the mechanical properties of HIP-treated MMCs by an optimized manufacturing process. The Ti-MMCs were fabricated by HIP and rotary swaging (RS) for secondary processing. The Ti-MMCs with different tungsten fiber contents of 0, 6, 9, and 12 vol% were subjected to tensile tests, fatigue tests, and hardness tests. The results show that the hardness values of Ti-MMCs increased with the increasing volume percent of tungsten fibers, the tensile strength increased by approximately 50% (specific strength: 38%) at the 9 vol%. The value of tungsten-fiber orientation F affects the tensile strength. The fatigue strengths of the Ti-MMCs did not improve. HIP is a useful manufacturing method for Ti-MMCs and RS is an important process for improving fiber orientation during secondary processing.

• Journal of Welding and Joining
• /
• v.25 no.6
• /
• pp.53-58
• /
• 2007

The present study examined the mechanical properties of the friction welding of shaft made of SKH51 and SM45C, of which the diameter is 12mm. Friction welding was done at welding conditions of 2,000rpm, friction pressure of 104MPa, upset pressure of 134MPa, friction time of 0.5sec to 2.5sec by increasing 0.5sec, upset time of 2 seconds. Under these conditions, a tensile test, a bending test, a shear test, a hardness test and a microstructure of weld interface were studied. When the friction time was 1.0 second under the conditions, the maximum tensile strength of the friction weld observed to be 963MPa, which is 89% the tensile strength of SKH51 base metal and 101% of the tensile strength of SM45C base metal. When the friction time was 1.0 seconds under the conditions, the maximum bending strength of the friction weld happened to be 1,647MPa, which is 78% the bending strength of SKH51 base metal(2,113MPa) and 87% of the bending strength of SM45C base metal(1,889MPa). When the friction time was 1.0 seconds under conditions, the maximum shear strength of the friction weld was observed to be 755MPa, which is 92% the shear strength of SKH51 base metal and 122% of the shear strength of SM45C base metal. According to the hardness test, the hardness distribution of the weld interface varied from Hv282 to Hv327. HAZ was formed from the weld interface to 1.2mm of SKH51 and 1.6mm of SM45C. Upon examination it was found that the microstructure became finer along with increase of friction revolution radius.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.6 no.1
• /
• pp.77-83
• /
• 1997

In this paper, we have studied internal quality including chemical compositions, microscopic structure and nonmetalic inclusion of test materials. We have analyzed dynamic characteristics of cutting force of milling including tensile strength value, hardness etc. Test materials are used in the tempered carbon steel and the non-tempered carbon steel. The obtained results are as follows: 1. In analyzing internal quality, the tempered carbon steel have typical martensite structure and the non-tempered carbon steel have ferrite + pearlite structure. 2. Yield strength, tensile strength and hardness value are in the non-tempered carbon steel but elongation is maximum value in the tempered carbon steel. 3. Cutting force is smaller non-tempered carbon steel than tempered carbon steel when feed speed and depth on cut is constant. 4. Cutting force is smaller non-tempered carbon steel than tempered carbon steel when cutting speed and depth of cut is constant.

• Journal of Welding and Joining
• /
• v.18 no.6
• /
• pp.42-47
• /
• 2000

The object of this study is to estimate Sn-Ag-Bi-Ga solder alloy as a substitute for Sn-37Pb alloy. For Sn-Ag-Bi-Ga alloys, Ag, Bi and Ga contents are varied. (Ag : 1~5%, Ga : 3%, Bi : 3~6%) Comparing to Sn-37Pb alloy Sn-Ag-Bi-Ga alloys have wider melting temperature range up to max. $18.7^{\circ}C$. With increasing Ag, Bi contents, the wettability of the alloys increased up to max. 6.6 mN. The vickers hardness of the alloys was max. 46.4 Hv. The ultimate tensile stress of the alloys was max. 60.3 MPa and the elongation was max. 1.2%. The joint strength between circuit board and solder was max. 55.5 N and the joint strength between connector and solder was max. 176.1 N. There were no cracks in this alloys after thermal shock test.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 1996.03a
• /
• pp.143-148
• /
• 1996

In this paper, we have studied internal quality including chemical compositions, microscopic structure and nonmetalic inclusion of test materials. We have analyzed dynamic characteristics of cutting force of milling including tensile strength value hardness etcs. Test materials are used the tempered carbon steel and the non-tempered carbon steel. The obtained results are as follows: 1.In analyzing internal quality, the tempered carbon steel have typical martensite structure and the non-tempered carbon steel have ferrite+pearlite structure. 2.Yield strength, tensile strength and hardness value are in the non-tempered carbon steel but elongation is maximum value in the tempered carbon steel. 3.Cutting force is smaller non-tempered carbon steel than tempered carbon steel when feed speed and depth of cut is constant. 4.Cutting force is smaller to the tempered carbon steel and smaller non-tempered carbon steel than tempered carbon steel when cutting conditions

• Journal of the Korean Society for Heat Treatment
• /
• v.24 no.5
• /
• pp.271-276
• /
• 2011

The effect of grain size on the deformation induced martensite transformation and mechanical properties in austenitic stainless steel with high amount of Mn was studied. a'-martensite was formed by deformation and deformation induced martensite was formed with surface relief. With increase of grain size, volume fraction of deformation induced martensite was increased. With the increase in degree of cold rolling, hardness, and tensile strength was rapidly increased with linear relationship, while, elongation was decreased rapidly and then decreased slowly. With increase of grain size, hardness and tensile strength was rapidly increased with linear relationship, while elongation was decreased rapidly. The hardness, tensile strengths, and elongation were more strongly influenced by deformation induced martensite than the grain size.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.19 no.6
• /
• pp.841-846
• /
• 2010

The present study examined the mechanical properties of the friction welding with hollow and solid shaft of SM45, of which the diameter is 25.2mm and 33mm. Friction welding was conducted at welding conditions of 2,000rpm, friction pressure of 50MPa, upset pressure of 70MPa, friction time of 0.4sec to 1.4sec by increasing 0.2sec, upset time of 2.0 sec including variable such as friction time are following. Under these conditions, a tensile test, a hardness test and a microstructure of weld interface were studied. The results were as follows : When the friction time was 1.0 seconds under the conditions, the maximum tensile strength of the friction weld happened to be 1,094MPa, which is 120% compared with the tensile strength of SM45C base metal. The upset length linearly increased as friction time increased. According to the hardness test, the hardness distribution of the weld interface was formed from 475Hv to 739Hv. HAZ(Heat Affected Zone) was formed from the weld interface to 2mm of SM45C.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.17 no.2
• /
• pp.65-70
• /
• 2008

This study deals with the friction welding of SKH55 and SM45C; The friction time was variable conditions under the conditions of spindle revolution 2,000rpm, friction pressure of 190MPa, upset pressure of 270MPa and upset time of 2.0 seconds. Under these conditions, the microstructure of weld interface, tensile fracture surface and mechanical tests were studied, and so the results were as follows. 1. When the friction time is 1.0 seconds, the tensile strength of friction welds was 926MPa, which is around as much as 84% of the tensile strength of base metal(SKH55), the bending strength of friction welds was 1,542MPa, which is around as much as 80% of the bending strength of base metal(SKH55), the shear strength of friction welds was 519MPa, which is around as much as 70% of the shear strength of base metal(SKH55). 2 According to the hardness test, the hardness distribution of the weld interface was formed from 964Hv to 254Hv. HAZ(Heat Affected Zone) was formed from the weld interface to 1.5mm of SKH55 and 2mm of SM45C.

• Journal of Welding and Joining
• /
• v.28 no.1
• /
• pp.66-71
• /
• 2010

With large specific strength and outstanding corrosion resistance and erosion resistance in sea water, titanium and titanium alloy are widely used in heat exchanger production. In particular, pure titanium demonstrates outstanding molding performance and may be considered optimal for production of heat exchanger. Since titanium is very vulnerable to oxidation and embrittlement during welding, processes with less heat input are widely used, and laser welding is widely applied by considering production performance and shield etc in atmosphere. So far, 1st report and 2nd report compared and analyzed embrittlement degrees by bead colors of weldment through oxygen and nitrogen quantitative analysis and hardness measurement, and evaluated welding performance and mechanical properties of butt welding. This study evaluated field applicability of lap welding to heat exchange plate of LPG re-liquefaction device for ships through tensile stress test, hardness test and internal pressure test etc after deducing optimal weding condition and applying to actual heat exchange plate. In bead overlap area, the experiment produced sound welds with no porosity or defect by increasing and decreasing laser power, and tensile-shear test results indicated virtually the same tension and yield strength as base metal. As a result of measuring hardness at lateral cross section and bead overlap zone of actual heat exchanger welds, hardness difference within 20Hv was produced at base metal, HAZ and weldment, and as a result of pneumatic and hydraulic pressure test, no leakage occurred.