Slit test and FISCO test already shows distinct result that the higher valve of Mn/S makes lower crack sensitivity for Cr-Ni austenitic weld metal. In this study, the effect of Mn for the character of Sulphide in the molten metal, especially weld metal, is researched. The experimental results make reason about the effect of Mn for the hot-cracking of weld metal as follows. (1) In molten Cr-Ni austenitic weld metal, Mn has the highest affinity to S ; Cr has intermediate affinity and Fe has the lowest one. (2) Therefore, the combination of Cr and S will form CrS in the Cr-Ni austenitic steel which con- tains less Mn or no additional Mn. (3) It is inferred that CrS is a principal reason for crack ; because CrS is formed on the austenitic grain boundary as impurity chains which make inferrior combination of grain each other. (4) By addition of Mn to Cr-Ni austenitic weld metal, CrS reacts on Mn and forms MnS. This is eliminated from molten metal as slag.
As the supplemental work to the previous paper, the electromagnetic force, which is included in the measured arc force, is estimated by some experiments and considerations. Then the measu-rements of arc force in MIG arc with Al, Cu and stainless steel electrodes are described. (Figs. 6, 7, 8). The results are discussed in relation to those given by other investigators. Some consideration is also made on the nature of arc force.
There are extremely close relations between the structure of a plastics and its mechanical properties. The structure of polyvinylchloride, which is a polymer of chain-form may be changed by an addition of plasticizer, or by controlling the temperature. Such materials are used most effectively and appropriately, by observing the changes of mechanical properties taken place in respective conditions. To extend their scope of application, various data concerning to 2nd transition were pursued.
To perform excellent welding work, and to elevate the reliability of welds, it is essential to perform with selected operating conditions when the fundamental conditions such as the shape of materials to be welded, chemical composition, welding position, etc. have been decided, the working condition is to be set on the basis of the welding condition which serves as the standard. Therefore, attempt was made to find such standard welding condition. Besides, in any of plastics for welding, the effect of air utilized as the welding gas is not a little under the high temperature at the time of welding, hence investigation was conducted so as to find a welding gas which will not adversely affect the welds. The standard welding condition for hot jet welding method should provide for such item as the thickness of plate, pressure of welding gas, quantity of the welding gas, temperature of the welding gas, welding speed, welding rod to be used, shape of the groove, number of layers, motion of filler rod tip, etc. That is, by prescribing the standard working condition, the substantial standard will be given for the designing of welds, so that it is useful to promote the efficiency of the welding work and mechanical properties of welds. Furthermore, study was made on the problems of welding gas in connection with polyvinylchloride, low-and high-pressure polyethylenes which are in general use as plastics for weldidg. Namely, in relation to the effect of the welding gas on the tensile strength of the weld produced in accordance with the standard welding conditions of respective plastics, and about the process of decomposition of respective plastics by high temperature welding gas, experiments and discussion were made. As indicated on the basis of the thickness of plate, the standard welding condition for polyvinylchloride will be as tabulated in Table 1. In actual welding, it is desirable to set the working condition, referring to the standard welding condition in relation to the fundamental conditions of welding such as the welding material, type of welding process, object of welding, welding position, etc. On the other hand, there exists the welding gas most suitable for respective plastics, and by use of such gases, the strength of welds will be increased significantly. Particularly, inert gas with admixture of hydrogen is effective.
Theoretical and experimental studies have been made on the formation of porosity in weld metal caused by the evolution of CO gas. CO gas potential, the ability of CO gas evolution of liquid steel, should be represented by the product of carbon and oxygen activities. Thus it has been given by the following equation: log ac⋅aso=-0.217[%C]-0.002[%Mn]+0.463[%Si]-0.34[%O] -0.061[%Cr]+1.045[%S]+… +log[%C] +log[%O]. This equation suggests that porosity is liable to occur in weld metal rich in carbon, oxygen, silicon or sulphur, and is hard to occur in it rich in chromium. Porosity occurs in weld metal, when ac⋅ aso is more than 4.0×10-3. Porosity grade of weld metal is closely connected with PI, where PI is given by the following equation: PI=(ac⋅aso-4.0×10-3)⋅[%O]
In this investigation, were studied on the following items to establish a proper spot welding procedure of titanium and its alloys. 1). Selection of foundamental spot welding conditions for titanium and α+β titanium alloys. 2). High temperature qualities of the spot welds of these materials. Consequently, found that titanium and 2%Al-2%Mn-Ti alloy have good properties in as welded, therefore, these can be said to have good spot weldability. And if a proper heat treatment after welding is performed (for instance, water cooling after heated in 600 to 700°C, or the post heat current pass into welds after spot welding, immediately), even 8% Mn-Ti and 4%Al-4%Mn-Ti alloys will be useful in some purpose for use.