In the submerged arc welding to analyze the transfer phenomenon of the metal (1) and the fo mation of the crater by arc in the covered flux (2), the X-ray radio photograph and oscilgraphic photograph tests are applied to the single electrode and multiple electrode welding. In taking the X-ray, the constant potential 280 KVP capacity to be used and the selected shutter speed of the photograph for transfering the metal and formation of the crater by arc to be 1/900 sec. and 1/50 sec. respectively. The A.C. welder and D.C. constant potential welder are to be used. Judging from the X-ray radio and oscilograph tests being practiced it is presumed that the transfering metal of the submerged arc welding is transmitted (dropped) irregularly as the fine grain. And the condition of the crater which is made by arc in other works the shape of the weld puddle and the relative positions between the weld puddles and electrodes differ depending upon the welding current, speed, voltage and electrode distance in the case of the multiple electrode process. It also confirms the relation between the shape of the weld puddle and bead appearance and penetration as well as the distribution of the electric current in the parallel connection welding method.
14mm steel plates (Wel-ten 50) and 20 mm steel plates (Wel-ten 55) of high tensile Mn-Si steels were used. The single bead was deposited on these plates and the change, by preheating with flame, of cooling curve about the heat-affected zone (the neighbourhood of fusion line), was investigated. According to this result, the cooling curve after welding shows a more gradual slope as the preheating temperaiure rises to about 350°C. The flatness of deposited metal, penetration, width of heat-affected zone and austenitic grain size increass as the preheating temperature rises. The hardness of welded part decreases considerably with preheating. The maximum hardness of the heat-affected zone for the Wel-ten 55 steel plate with 20 mm thickness is very high in case of no preheating. In this case, martensite appears on about 45% area of the part of the maximum hardness and the hardness is about 312 in Vickers hardness number, but when preheating is done it becomes remarkably lower value and is 210 in case of about 350°C preheating. Judging by the cooling curves after welding and the existence or non-existence of constituents in microstructure of heat-affected zone, two fields., showing existence of constituents, divided by a critical cooling curve are clarified. Further., the micro-Vickers hardness of each consituent was measured.
Total oxygen content in weld metal is usually several times higher than in general rolled steel. Oxygen content which is soluble in matrix is extraordirary low, therefore almost oxygen exists in the form of non metallic inclusions. Attempts have been made to extract non-metallic inclusions to carbon film to be studied with on electron microscope. By the electron microscope the very minute non-metallic inclusions such as smaller than lμ can be direct observed. The size, shape, constituents ahd other characteristics of non-metallic inclusions have been determined by means of electron diffraction method and direct observation. The author tried to obtain rather simple non-metallic inclusions and used single deoxidizer such as silicon, manganese, titanium, etc. The core wire, its carbon content is very low and its silicon and manganese contents is reduced to neglsible small, was used in this investigation.
This is to report about a welding experiment perform cd in joining heat treated rails with the hardness of 308-390 Hv and high abraision resitance. The following are the results summarized with some comments : - 1) In joining heat treated rails by manual arc welding, satisfactory joint strength can be obtained, when the bottom and web are welded with low hydrogen type electrodes, following 90% of the top part welding by means of the same type electrodes, and then the head surface is built up about 10 mm deep with the intention of hardfacing. The joining strength does not change by hard surfacing. 2) For padding the employment of Mn Austenite type or Martensite type electrodes cannot be recommended, because of the cracks occurring at the fusion line between padding and base metals. We advise the use of low Cr steel type electrodes whose welding hardness is compatible with that of rail head and the welded metal is difficult to cause cracking. 3) By welding, the surface hardness of rail head is softened over the range of about 10 mm from the fusion line. Rails post heated for 30 min. at 600°C immediately after welding tend to be softened down to about 250-280 Hv. over the heating zone, but the micro-structure of the point 50mm apart from the fusion line is not remarkably changed, compared with the base metal structure. 4) As the result of passing trains for 80 days, it is recognized that the hardness of welding metal and softening zone of wheel side is inclined to increase by the cold working (train pass load ; 38, 000 ton/day) up to 2 mm depth under the head surface. 5) The abraision loss of the base metal, the post heated softening zone and the deposit metal are almost equivalent 2 1/4 years after construction (train pass load 8, 200, 000 ton/year, gradient ; 15/1000, straight track of 348m), and the local abraision can't be observed. It is therefore considered that this weldng procedure can be used practically.
Making some improvements on the mechanism and testing procedure of Murex rotational fillet hot crack test, we investigated the effect of rotational speed, welding condition and chemical composition of weld metals on the hot crack sensitivities of various electrodes. Contrary to the original report by Jones, our test has shown that high machine speed tends to give longer crack length, and there is a critical strain speed in the critical temperature range to start cracking. Sulphur has the most deleterious effect on resistance to hot cracking, and it may be concluded that the extended existence of liquid film stage is the cause of hot crack.
The under-bead-crack is often seen on the high carbon and the alloy steels. But on the mild steel, if the constraint is severe for welding, mother-metal-crack is caused not only immediately under bead but at heat affected and not affected zones. In this research, using semi-killed, Si-killed and Al-killed steels, the crack sensitivity test in which a specimen is extended in the direction of the thickness of plate by the shrinkage of weld metal and the constraint was performed. And the mother-metal-crack of the mild steel was examined from the points of view of the hardenability and the cleanliness of material and the condition of constraint.