Authors reported already that, when joining Fe to alloying elements commonly found in steel, such as C, Cr, Co, Ni and W, with Cu filler metal, a "dissolution and deposit of base metal" took place. In this paper, the configuration of the dissolution and deposit in Cu brazing to dissimilar alloy steels containing those alloying elements was investigated metallographically. The shear strength of the brazed joints was also examined. In joining low and high C steels to high speed tool steel and stainless steel, C of alloying elements exerts the greatest influence on the dissolution and deposit-that is, the lower C base metal when compared to the other one dissolves into molten Cu filler metal and, simultaneously, the columnar Fe alloy phase deposits from the higher C base metal under a constant brazing temperature. The shear strength of the joints, with the exception of stainless steel-high C steel joint in which a chromium carbide forms at the high C steel boundary, remarkably advances by linking both base meatls with this columnar deposited phase.
The flash welding consists of the flashing and the upsetting actions, and has a number of variables for the processes. The purpose of this study in Part one is to examine the flashing phenomena in carbon steels and ferritic or austenitic stainless steel sheets in 1.2 mm thick. The flash welding was carried out using the constant rates of the platen acceleration and the secondary no load voltage of 12.2V and below. The following results were obtained. 1. The flashing current waveform in each half cycle consists basicaly of the three phases of bridge, flash and open. The ratio of these phases results in a nearly constant value at the early stage of the flashing process. 2. In the late stage the ratio of these phases in low carbon steel shows the same values as that in medium carbon steel, but a little difference from that in austenitic stainless steel. 3. The ratio of these phases and the numbers of flash in a unite time are remarkably affected by the variations of the size of specimen, platen speed, secondary no load voltage and electrical circuit constant of the welding equipment, and the remarkable firing of flash generates under the secondary no load voltage of about 6V.
When the arc run-off onto the terminal end tab plate in one side submerged arc welding, the restraint by tack welding is released and rapid rotative distortion acts upon the weld metal just after solified and creates the end crack. And the quantity of rotative distortion influences upon the frequency of end crack. Slit tab plate which restrict the end of weld joint flexibly can avoid rapid rotative distortion and is effective on prevention of end crack.
3.5% Ni steel for low temperature service was subjected to some synthetic welding cycles. These J integral fracture toughness, JIc and critical crack-tip opening displacement, δc were obtained through three point bend test conducted at low temperature range from -196°C to -80°C. The main results obtained were as follows; 1) Judging from the results of manual weld sample with covered electrode (3.5% Ni and 6.5% Ni) through V-notch Charpy impact test, the absorbed energy was better in the following order. base metal>weld HAZ> weld metal But the energies of synthetic HAZs were much inferior to those of weld HAZ mainly due to grain coarsening. 2) JIc values and δc values in synthetic HAZ were inferior to those of as-received steel in evrey test temperature. But the remarkable recovery of JIc and δc was obtained in synthetic HAZ by a reheat of the temperature at 700°C to 800°C and a rapid cooling, which was due to the formation of a tempered martensite and a bainite structure. Fracture toughness of the reheated synthetic HAZ was about two to three times larger compared to that of as-received specimen. 3) Maximum JIc and δc were observed at 18 to 40 see, chanigng the cooling time from 800°C to 500°C in synthetic HAZ, which was heated at peak temperature of 1300°C.
The phenomenon of fume generation from filler metal in a brazing process is well known, and it is said that the fumes will cause an undesirable effect on the health, but the study about fumes concerning brazing has hardly been reported on. The authors tried measuring and analysing of fumse using fume-collecting equipment which was specially designed by the authors. The experimental results were as follows. 1) Among many kinds of filler metals, brass, BAg-4, and Bcup-2 produced comparatively larger amount of fumes in the brazing process. 2) The main constituent of the fumes produced during brazing was zinc in the case of brass and BAg-4, and phosphorus in the case of BCup-2. 3) The shape and size of the fumes were different according to the kinds of filler metals, and the size of the fumes was about lμ-10μ.
Heavy sectional structural steels for nuclear pressure vessel are severely required to prevent unstable fracture like a brittle fracture. From this point of view, it is important to know the fracture toughness characteristics concerning to the fracture mechanics criteria for evaluation of fracture toughness. Dynamic fracture behaviors of the steel in tensile test using circumferentially notched round bar specimens were reported and discussed previously. In this report, dynamic fracture toughness test using three points bending specimens of the same steel are carried out, and the evaluations by the critical COD, J-value and dynamic transition temperature are investigated. The conclusions obtained from the experimental test results were as follow; 1) Transition curves of dynamic fracture toughness shifted to a higher temperature, and transition curves were change in narrower temperature range abruptly as higher impact loading rate. 2) Transition temperature Tdδ(0.2) or TdJ(10) based on the dynamic COD or J-value criteria re-spectively were almost constant or slightly increased to higher temperature with higher loading rate. 3) The difference of transition temperature between the static and dynamic fracture test was large in the bending fracture toughness test comparing with the tensile test. 4) The dynamic COD or J-value criteria in this test represented a favourable critical toughness of the structural steels depending to test temperature.