Weldability as related to the heat-affected zones of the quenched and tempered steels, 2H (HT 60), were evaluated by means of V-Charpy impact and round bar tensile tests of synthetic HAZ specimens. Firstly, the effect of peak temperatures of termal cycles, 500, 650, 750, 900, 1100, 1300 and 1400°C, on the impact and mechanical properties of synthetic HAZ specimens were obtained. According to the tensile tests; softened zones have been observed in two locations, that is, the tempered and recrystallized zones. From V-Charpy tests, however, it was assured that these softened zones did not give any adverse effect on the notch toughness of these steels. Furthermore, the effect of the rate of cooling followed by thermal cycles from a peak temperature of 1300°C, were examined. The toughness of the coarse-grained HAZ microstructures were increased with the increase of the rate of cooling, while the tensile ductilities were decreased on the contrary. Then, these properties were intimately related to the transformation products. Finally, it was mainly concluded that the toughness and tensile ductilities were generally satisfactory and then should have about the same as those of the ordinary high strength steels usually employed.
Hot ductility, as revealed the values of reduction in area at the fracture surface tested at high temperatures on the weld thermal cycles, was studied on austenitic stainless steel weld metals by means of a reproducing apparatus of weld thermal cycles. Five weld metals, including type 308L, 347 and 316, were tested in this study. A round bar tensile specimen made from multiple pass weld, was heated rapidly up to the peak temperature of 1350°C and then broken at each temperature of 800, 1000, 1100, 1200 and 1300°C both on heating and cooling along the thermal cycle, respectively. From the tests, hot ductility curves, expressed as percent reduction in area at fracture as a function of the testing temperatures were obtained for each weld metal. From the values of reduction in area as measured both on heating and cooling at 1200°C, hot ductility rating about these weld metals was determined as the following order. On heating-308L [347(A), 347(B), 316] 347(C) On cooling-308L [347(A), 347(B)] 316, 347(C) Among the test weld metals, the hot ductility of type 308L was the most superior, while that of type 347(C) containing no ferrite was the poorest on the contrary. Furthermore, the comparison was made between hot ductility and Fisco cracking test results for the test weld metals. A close relationship was found between the two, then the hot ductility was assured to be effective extensively as a measure of hot cracking susceptivility of austenitic stainless electrodes.
With the purpose of studying the weld metal cracking of AISI Type 347 austenitic stainless steel which is essential for nuclear applications, modified FISCO type cracking tests were performed with combinations of plate thickness. 12mm and coated electrodes of several types. In the present paper, the relationship between test conditions and cracking tendencies were mainly investigated and the test procedure in the present report was a little different from the original proposed by Dr. Schnadt. The con-clusions obtained are summarized as follows : (1) It was cleared that the modified FISCO type crack test was adequate for weld metal cracking test of austenitic stainless steel. (2) The crack at the start of a weld bead was propagated with an increase of welding speed or root opening. (3) The crack at the crater of a weld bead was propagated with an increase of welding current or arc voltage. (4) The bead cracking tendency was remarkably increased with a decrease of welding heat input and the crack was finally extended along the whole length of the bead. This tendency remarkably affected by shape of groove, root opening, type of electrode and etc. (5) There was considerable diffirence in cracking susceptibility among the tested several electrodes of Type 347 and Croloy 16Cr-8Ni-2Mo, the latter electrode showed less susceptibility than Type 347.
In this report T-T-T diagram and CCT-Curve from austenitizing temperature 1200°C were researched and then effects of preheat temperatures and welding thermal cycle on properties of heat affected zone were clarified to investigate weldagility of 21/4 Cr-1Mo steel and also we carried out a restraind crack test to investigate crack sensitivity of the steel. The results of experiments are summarized as follows : (1) As shown in Fig. 1 T-T-T diagram have two noses at A1 and Ar' transformation ranges. (2) A1 transformation rate in CCT-Curve (Fig. 2) is suppressed remarkably. (3) With raising preheat temperature, maximum hardness in the heat affected zone decreases and toughness improves. (4) Welding heat affected zone which is hardened by the first pass at the range of preheat temperature 200-300°C is heated over the A1 transformation temperature by following welding thermal cycle and its mircostructure is refined. (5) According to results of restrained weld cracking sensitivity test, crack in the weld zone is vented by preheating to 200-300°C.
The end of steel bar specimens with various diameter have been heated by mean of oxy-acetylene tips (capacity : 500;) with single and multi nozzles that is nearly equal to flat theamic source as is shown in Fig. 5, in order to measure the thermal efficiency of oxy-acetylene flame and the heat transfer coefficient between heated surface of bar specimen and the flame. The test results can be described as follows ; 1) The heat quantity corresponded to 35% in total transfered heat quantity was given from the front or top of white cone to the specimen. This decision was based on the test results as is shown in Fig 1, 2, 4 and 7, and the result of consideration for them. 2) A few matters should be studied are remained, however, the authors introduced the formulas (1) and (2) on the instantaneous and mean heat transfer coefficient between bar specimen and the front on top of white cone in the heated period. In this case, the temperature in front or top of white cone was assumed 3, 200°C.
The CO2-O2 arc welding of thick plate of 52 kg/mm2 high tensile steel was carried out with various conditions for butt joint. Plates in 20 and 32 mm thickness were used. It was easy to get a complete penetration by one pass welding at each side in case of I or X butt joint of plate in 20 mm thickness, but not easy in case of X or V butt joint of plate in 32 mm with groove angle less than 45 degree. Moreover, as decrease of groove angle, the tendency of root-bead cracking increased. In conclusion, U butt joint is more desirable than 60 degree Vee or X-butt joint. The mechanical properties of such joint of 52 kg/mm2 high tensile steel plate in 32 mm thickness were the same as or over those of the base metal.
In this paper, the authors describe on the results of Amsler tensile test and Shore, Vickers, Rockwell hardness tests concerning the size effect of unplasticized polyvinylchloride. The results of these experiments are considered to show that unplasticized polyvincylchloride has a tendency to become larger value in larger specimens than in smaller ones. We have found that, unplasticized polyvinylchloride has size effects in these experiments, and the size effects are larger in the specimens than in metals, and then hardness testing method of unplasticized polyvinylchloride is considered better in Martens hardness test than in Shore, Vickers and Rockwell hardness test.