• 한국주조공학회지
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• 제34권4호
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• pp.136-142
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• 2014

Numerical solution of thermal stress by CAE analysis could be an effective method in product development stage of castings to predict and treat the problem of solidification cracking of castings. Quantitative stress-strain data are necessary, in this case. Tension type apparatus of a solidification crack test which can measure stress-strain relationship quantitatively was developed and the test procedure was established by this research. Solidification crack strength obtained from the following test procedure could be utilized to evaluate it in terms of effect factors on thermo-plastic characteristic of solidifying alloy such as grain size of solid, grain morphology, distribution of solid grain, etc. Proposed test procedure is as follow: Prediction of temperature at the failure site of solidification cracked specimen by computer simulation of solidification, Calculation of solid fraction of the failure site from thermodynamic solution of solidification under Scheil condition.

• 한국주조공학회지
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• 제34권5호
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• pp.162-169
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• 2014

The effect of the mold preheat temperature on the solidification crack strength was investigated in AC2B aluminum alloy. A tension type apparatus as part of a solidification crack test which could measure the stress-strain relationship quantitatively was utilized. The evaluation of the solidification crack strength with varying mold preheat temperatures was performed by the test procedure established in this research. When the mold preheat temperatures were $250^{\circ}C$, $150^{\circ}C$ and $50^{\circ}C$, the solidification crack strengths were found to be $7.8Kgf/cm^2$, $12.9Kgf/cm^2$ and $28.6Kgf/cm^2$, respectively. In the same way, when the mold preheat temperatures were $250^{\circ}C$, $150^{\circ}C$ and $50^{\circ}C$, the corresponding temperatures of the failure sites were $610^{\circ}C$, $600^{\circ}C$ and $571^{\circ}C$, and the calculated solid fractions were 14.0%, 29.3% and 50.8% when the specimens failed, respectively. The solidification crack strength increased in proportion to the solid fraction of the failure site. The solidification crack strength obtained in this test is assumed to reflect the effects of metallurgical factors on the thermo-plastic characteristics of a solidifying alloy such as the grain size of the solid, the grain morphology, and the distribution of solid grain.

• Journal of Welding and Joining
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• 제30권3호
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• pp.57-65
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• 2012

The interest of austenitic heat resistant stainless steels containing high Si has increased because they have higher resistance of oxidation and higher strength at high temperature than STS 310. This study carried out Varestraint test for evaluation of solidification cracking sensitivity of 14 different stainless steels. As a result of Varestraint test, all specimens solidified as primary ferrite, and solidification crack sensitivity increased with adding $N_2$ to shielding gas. Nb and W had beneficial effect on solidification crack resistance in case of less than FN 2 containing, but crack sensitivity increased with Nb and W in case of more than FN 2. Ce had beneficial effect on solidification crack resistance but impaired weld bead appearance.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.577-582
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• 2002

The solidification cracking susceptibilities of AI-Mg-Si alloy laser welds were assessed using the self-restraint tapered specimen crack test. The cracking susceptibility of 6061 and 6082 Al-Mg-Si alloy laser welds was substantially reduced when the filler wire containing high Si such as Al-12 wt.% Si (4047A) was used. The amount of eutectic was observed to affect the solidification cracking of Al-Mg-Si alloy laser welds. Abundant eutectic seems to heal the cracking and reduces the cracking susceptibility, while an initial increase in eutectic liquid leads to the increased cracking tendency.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2000년도 추계학술대회 논문집
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• pp.236-239
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• 2000

It is important to evaluate austenitic heat resistant stainless steel because of low weldability of austenitic heat resistant stainless steel containing high Si. This study took varestraint test for evaluation of solidification cracking sensitivity and Erichsen test for evaluation of weld metal ductility. As a result of tests, solidification crack sensitivity increased with adding $N_2$ to shielding gas, and W had detrimental effect on crack resistance, but Ce had beneficial effect on crack resistance. Under same heat input, ductility of weld metal increased with welding speed.

• Journal of Welding and Joining
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• 제19권6호
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• pp.614-621
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• 2001

A study was carried out to determine the solidification cracking susceptibility of Ni-base superalloy as a function of Fe content in base metal. Three kinds of Ni-base superalloys with three different levels of Fe content were used. The solidification cracking susceptibility was evaluated by the Trans-Varestraint test at four different strain levels. Quantitative analysis of crack revealed that the solidification crack length and the temperature range in which hot cracking occurred in fusion zone (Brittle Temperature Range, BTR) decreased with a decrease in Fe content. Further, the thermo-calc data indicated that the solidification temperature range also decreased with decreasing Fe content. From these results, it was deduced that the improvement of the solidification cracking susceptibility with decreasing Fe content was attributed to the decrease of the solidification temperature range.

• International Journal of Korean Welding Society
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• 제2권2호
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• pp.42-46
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• 2002

The solidification cracking susceptibilities of Al-Mg-Si alloy laser welds were assessed using the self-restraint tapered specimen crack test. The cracking susceptibility of 6061 and 6082 Al-Mg-Si alloy laser welds was substantially reduced when the filler wire containing high Si such as Al-12 wt.% Si (4047A) was used. The amount of eutectic was observed to affect the solidification cracking of Al-Mg-Si alloy laser welds. Abundant eutectic seems to heal the cracking and reduces the cracking susceptibility, while an initial increase in eutectic liquid leads to the increased cracking tendency.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1995년도 특별강연 및 춘계학술발표 개요집
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• pp.65-67
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• 1995

The solidification crack susceptifility of aluminum alloy weld metal have been evaluated by means of the slef restraint and external restraint cracking test. It has been observed expermently as follows : (1) The manganese is beneficial to decrease the solidification cracking susceptibility. (2) Weld metal containing zirconium is less sensitive to the solidification cracking than the weld metal containing chromium does. (3) The self restraint test method shows the same tendency in results as the external restraint test does.

• International Journal of Korean Welding Society
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• 제1권1호
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• pp.63-70
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• 2001

The solidification cracking susceptibilities of Al-Mg alloy laser welds were assessed using self-restraint tapered specimen crack test. The dependence of cracking susceptibility of Al-Mg alloy laser welds on Mg contents was observed to be similar to that of arc welds in the same materials. The cracking susceptibility of Al-Mg alloy laser welds increased as Mg content increased up to 1.6-1.9 wt.% and then it decreased as Mg content increased further. The peak cracking susceptibility occurred at around 1.6 to 1.9 wt.% Mg for both autogenous and wire feed welds. It was also observed that the cracking susceptibility decreased as the grain size of Al-Mg alloy laser welds decreased, when Mg content was in the range higher than 1.9 wt.%.

• Journal of Welding and Joining
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• 제22권5호
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• pp.65-72
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• 2004

The tendency and degree of hot cracking of high strength 5083, 6N01 and 7N01 Al alloy welds by using DCSP-GTAW through modified Varestraint test and autogenous butt welding were investigated. In hot cracking test, 6N01 alloy showed the highest susceptibility to hot cracking in the weld metal and HAZ. Cracking susceptibilities generally increased with increase of solidification temperature range of the base metal and bead penetration-to-width ratio of the weld metal. The cracks in welds of the alloys vertically formed to solid-liquid interface and propagated along with columnar grain boundaries. The fracture facets of cracks showed the typical morphology of solidification crack observed as dendritic structures. Especially, in 6N01 alloy, liquation cracks which were due to elements of Si, Fe and Mg also observed in HAZ near fusion boundary. In butt welding of different Al alloys, the bead crack was mainly occurred in the welds of 6N01, 7N01 and other Al alloys together with 6N01 or 7N01. In the butt welds of 7N01, it was found that the component of Cu had an effect on the higher susceptibility to the hot cracking.