Weld decay in HAZ of austentic stainles steels has been evaluated with loss in weight by method of nital-fluoric acid test. But it cannot evaluate correctly, because it has the following problems. (1) Corrosion of cross side is serious compared with surface side, therefore total loss in weight is affected with the loss on the cross side in case of improper dimentsions of test piece. (2) Evaluation of weld decay is affected the quantity of weld decay on bottom side in spite of the same depth of that on surface side. (3) Weld decay of welds with narrow bead is evaluated greater than that of wide bead. The goal of this experiment is to develop a new evaluation method of weld decay. Accordingly in order to solve the said problems, we tried comparison test between voltage drop method and loss in weight by nital-fluoric acid method, using test pieces made with MIG welding, underwater MIG welding and electron beam welding. Results of experiment told us that evaluation by the former was more suitable than that of the latter.
This paper presents some experimental data concerning the relation between the shearing strength and roughness of base metal (mild steel) surface brazed with BAg 8. The specimens used in this experiment were made according to the configuration ofJIS Z3194, the same shape as designed by F.M. Miller and R.L. Peaslee. To make the various roughness on the base metal, each specimen was identically finished by means of abrasive paper (60, 120, 240, 400 and 600 mesh) polishing and milling cutting or WA60 and WA80 wheel grinding. The brazing operations of these specimens were conducted using a 35Kw resistance furnace operated in hydrogen atmosphere, and joint clearance of each specimen was adjusted on the cementing fixture. To obtain the tensile-shearing strength value of these specimens, 50 tons tensile testing machine was used in this experiment. Tensile-shearing test of these specimens gave the results as follows: (1) As regards the relation between the shearing strength of brazed joint and roughness of base metal surface, it was clear that shearing strength of brazed specimens having a small roughness value was greater than that of one having a large roughness value. (2) The maximum shearing strength of brazed specimen was observed at the about 0.3 mm joint clearance. (3) It was cleared that shearing strength of specimen having a long brazed joint length was lower than that of one having a short brazed joint length. (4) Most of specimens failured at the filler metal zone, and a few of them failured at the interface of joint, but no specimen ruptured in the base metal.
In diffusion welding, ideal atomically flat and clean surfaces are capable of bonding spontaneously when brought into intimate contact which produces the metallic bond. However the properties of real surfaces affect the quality of welds. This paper describes the influence of process parameters on the joining process, using copper, surface contamination of which does not seem to have so strong effect on weldability. Especially the diffusion welding process is investigatedd from the characteristic value at high temperature that is measured in terms of investigation of the welding process between conical specimen and flat one. The following results were obtained. 1. The result obtained from investigation about the welding process between conical specimen and flat one: A) The ratio (As) of the projected area of the indentation to the load does not depend on angle of cone (30°-160°) and load (8.24 kg). B) The ratio (As) is the mechanical characteristic value at high temperature, and is formulated by temperature and time. C) Tensile strength of the contacting part is coincident with one of the base metal. 2. The result obtained from investigation about the butt diffusion welding process of bar: A) The results obtained from welding process between conical specimen and flat one can be applied even in the case of bar. B) Real contact area is calculated by As⋅WL/A (WL: welding load, A: apparent area). C) Joint strength is calculated by K⋅As⋅WL/A⋅SB (K: material constant, SB: tensile strength of base metal). But the finer surface roughness is at higher temperature, the higher the joint strength is than calculated value. D) Welding deformation is closely related to As⋅WL/A.
It is well known that welding deformations influence strength and ductility of weldments. In the present report, attention is forcussed to the effect of welding conditions, such as weld heat input, physical and mechanical properties of materials, size of weldment etc, on welding deformations in surfacing weld. Parameters which dominates welding deformations are deduced by the use of theories of heat flow and thermoelasto-plasticity. Experiments are carried out under various conditions, changing weld heat input, plate thickness and material, for investigating the effect of those parameters on welding deformations. From this study. the following informations are obtained. (1) Welding deformations are determined by the following parameters; (a) Heat input T0*=α0Q/cρεY0h2 (b) Initial temperature θi*=α0θi/εY0 (c) Temperature above which yield stress becomes zero θM*=α0θM/εY0 (2) Welding deformations are determined by parameter Q/h2, θi when material is same. (3) In the case of mild steel, welding deformations are not depend on welding processes such as GMAW, GTAW, SMAW and SAW, when Q/h2 is less than or nearly equal to 2500 cal/cm3. (4) Conventionale formulae to calculate welding deformations are derived from the theory and experimental results.
Relating to cold cracking in steel welds, restraint stresses and strains are studied theoretically for the slit weld, in which a slit is made in an infinitely large plate and welding is done into the slit. Restraint of weld will be higher at the ends than at the middle part of the slit. Assumptions used in the analysis are that 1) welding heat is given instantaneously along the length of a slit and 2) throat thickness of weld is rather small as compared with the plate thickness. These assumptions are enable us to make elastic analysis concerning stress-strain in the plate even when general yielding occurs in the weld metal. According to a model considered for obtaining the restraint severity in the weld metal along a slit, restraint deformations in the weld are given by the sum of the elastic movement of the slit edges at elevated temper atures and the contraction of weld metal. Plastic part of the restraint deformations will be a measure of restraint severity in slit weld. It is obtained along a slit as functions of variables such as length of slit, thickness of plate, weld heat input, yield strength of the material etc. General yielding in the wed metall occurs over a certain length near the ends of a slit. The restraint deformation or restraint strain become maximum at a location apart the value of critical plate thickness, or 15-20 mm in shielded-metal-arc-welinbg of steels, from the ends of a slit. Examples of them are calculated for steel welds.
Theoretical formula is newly derived for temperature rise of any point in thick mother plate when a constant point heat source of velocity v moves in infinite wide mother plate. The formula is expressed in form of error function. See equ. (I4) Fig. 2 shows the temperature curves of starting and stopping points and we see the temperature of starting point is a little higher than that when velocity is increased to infinity.