The development and evaluation of various weldability tests and investigation of the effect of alloying contents on the weldability of Mn-Si high strength steels were performed using 12 experimental steels, with additions of 1.2% silicon and/or 1.8% manganese. The present paper describes the results of a tapered maximum hardness test, bead-bend tests and synthetic HAZ ductility test, which was newly proposed by the authors. From above results, the main conclusions were obtained as follows: 1) From a tapered maximum hardness test, it was recognized that weld HAZ hardness was increased remarkably by manganese addition, but a little by silicon. 2) As a results of the comparison of various miniatured specimens with the longitudinal bead-bend-test specimen of Kommerell type, one small type specimen was newly introduced as a substitute for the standard type. 3) HAZ ductility which was obtained by the synthetic HAZ ductility test showed remarkable loss with increasing manganese contents but was almost unaffected by silicon contents. 4) Intimate relationships were established between the results of a small type bead-bend test and a synthetic HAZ ductility test, especially in critical hardness values which showed unsatisfactory HAZ ductility.
Recently much efforts have been done in the field of physical chemistry of welding process. In this work an attempt is made to evaluate the sulphur distribution of basic weld metal. The degree of basicity of slag is changed by varying the ratio of CaO to SiO2. To remove sulphur from the weld metal a high basic slag is more effective than an acidic slag, and log K'si, s becomes propotional to the basicity BL. The values of log Ko' and log K'Mn can not be constant throughout the whole range of expcrimental slag, and log K'Mn takes a higher value at the acidic side whereas log Ko' gradually increases at the basic side of slag. In the range of acidic slag log K'Si increases proportionally to basicity. Through deoxidation by manganese in the basic covered electrode weld metal silicon would not enter the weld metal until the basicity of slag dicreases below the BL of 0.8. The oxygen content of a weld metal containing sulphur is much higher than on ordinary weld metal.
A high-voltage electrcn-beam welding machine with a maximum beam power of 1.5 kw (50 kV, 30 mA) has been operated in the Japan National Research Institute for Metals since July 1960. With this equipment, the characteristics of bead penetration and welded joints of Zirconium and Zircaloy-2, namely, microstructure, hardness, tensile and bending properties and corrosion resistance against high temperature, high pressure water studied as compared with the case of TIG welding, and the following conclusions were obtained : (1) It is possible to make a butt-joint weld at a high welding speed such as 40 to 100cm/min up to about 2.0 mm thickness of sheet. (2) Relationship between specific weld heat input and ratio of bead penetration-to-width is given by following equation. w/p X 100=76 log H-45 (3) About three times the specific weld heat input of electron beam welding is necessary for TIG welding to give the same bead penetration. (4) To make a smooth and not-burn - through welding bead, it may be supposed that a low voltage type power source should be preferred type, especially, for a thin sheet. (5) No evidence has been found to substantiate the occurrence of a change in oxygen and nitrogen composition due to this welding process. (6) Metallography, hardness, mechanical-property evaluations and corrosion tests have revealed satisfactory properties in Zirconium and Zircaloy-2 wleded joints by this welding process.
Weld cracking of high strength steels is one of the most impotant factors of weldability and a large number of test methods have been proposed to study cracking. Among those methods, the butt weld cracking test specimens of Lehigh restraint (U-groove) and Tekken (y--groove) types were selected for an extensive study of cracking properties of mild steels and electrodes for a range of tensile strength between 40 and 90 kg/mm2. Effects of groove shape, welding heat input, preheating temperature, immediate postheating, coating type and strength of electrode and chemical composition of steel on cracking behavior and instant of crack initiation were investigated to search for a reasonable method of cracking test of high strength steels and electrodes. Cracking behavior of high strength steels and electrodes is very differently affected by shape of groove in specimen, especially with Lehigh type symmetrical U-groove and Tekken type oblique y-groove. Therefore, two different types of groove should be used to differentiate cracking susceptibility of base metal from that of electrode ; that is, y-groove is more preferable to base metal testing, while U-groove or Y-groove to electrode. Since there are a number of cracks which do not appear upon the face of weld, cracking should better be examined in cross section or on root of weld rather than on face only. The cold cracking in this investigation occurred more than three minutes after welding at temperatures below 90°C, regardless of steels, electrodes and preheating temperatures. Although the effect of preheating was remarkable in preventing cracking, a postheating of weld HAZ at 600°C immediately after welding within two minutese was found very effective in obtaining a crack free weld even without preheating.
It is necessary to use a supplied gas having humidity as low as possible for gas-shielded metal arc welding. But it is not always easy to get everywhere the recommended gas for welding, i.e. super-pure and super-dried gas charged into a specially treated cylinder. The authors carried out experiments about drying of gas supplied from a cylinder with some desiccants : sodium alumino silicate, activated alumina and silica gel. The dew point of the gas flowing out through a desiccator was continuously measured until the given amount of a desiccant broke. Carbon dioxide was used for the supplied gas. The results are as follows : 1) Sodum alumino silicate has a drying capacity larger than activated alumina and silica gel. The sodium alumino silicate of 640 g warrants a supply of CO2 gas under -25°C dew point for 112 hrs., i.e. 7 cylinders. The dew point of gas through the desiccant is under -40°C from the first cylinder to fifth. 2) Activated alumina and silica gel warrant a supply of only two cylinders of CO2 gas under -20°C dew point through each desiccant. 3) An experimental formula was established for the relation between charged weight of sodium alumino silicate and break-time.