Papers by Keyword: Fusion Line

Abstract: The present work focuses on the microstructural changes that occur in the partial melted zone in welds made on some cast designated alloys. The aim of the work is to improve the available data related to PMZ morphology, properties and possible mechanism involved in the final metal response. It demonstrates that for binary alloys little changes occur in PMZ; in case of a complex alloy the changes are more consistent affecting both primary and eutectic structure when interstitials are involved. It proves also that the morphology of PMZ depends on the filler metal properties.

Abstract: The design and fabrication of offshore structure depend on material science and solid mechanics, such as steel processing technology and welding and materials testing and evaluation and so on. In this paper, CTOD (Crack Tip Opening Displacement) toughness test for weld joint of heavy thickness S355G10+N steel has been carried out to evaluate the fracture resistance of this weld joint under Submerged Arc Welding(SAW). The results show that (1) the weld joint of heavy thickness S355G10+N steel tested possesses excellent toughness. That is to say the materials in the weld joint possess enough capacity resisting the crack and propagation. Therefore the welding procedure specification evaluated can be applied to fabricate offshore structure. What is more, being at the case of as-weld condition for the weld joint the CTOD test was carried out herein, hence the offshore structure fabricated with the welding procedure specification evaluated can avoid the post welding heat treatment. (2) Different positions in weld joint have their special toughness. The position which is 2mm away from the fusion line (located in base metal) (FL+2) possesses best toughness (average value is 0.825mm). The fusion line position (FL) possesses slightly worse toughness (average value is 0.672mm). The weld metal position possesses worst toughness (average value is 0.553mm). This distribution character is different from other references reported and comparision has been made in this study. (3) Being a lower fracture toughness in weld metal, as a design suggestion high stresses should be avoided in this position.

Abstract: Power plant weldments are composed of various microstructures. Due to welding and PWHT processes, the microstructure of the base metal adjacent to fusion line is transformed into entirely different microstructures, collectively known as heat affected zone (HAZ). Creep, on the other hand, is considered as the most important deterioration mechanism of heat resistant components found in power plants. Therefore it is essential to evaluate creep properties of HAZ, which is considered to be very hazardous in weldment. Recently, most of the creep tests for HAZ are conducted using cross weld type specimen. However there are some problems with this type of creep test due to the results being largely varied according to the volume fraction of HAZ. In this paper, SP-Creep test, which has confirmed the availability for creep properties evaluation, has been conducted on each of the weldment microstructures. The results showed that each microstructure has a different creep behavior. The overall creep properties of HAZ are worse than those of the weld metal. Among the HAZ structures, fine grained HAZ has the worst creep properties.

Abstract: Fatigue strength and life of weldment at high temperature is very important for high temperature materials used in power plants. In this study, fatigue crack growth tests were performed at high temperature to examine the effect of microstructure on the crack growth resistance in P92 steel weldment. Microhardness of the weldment was also investigated for better analysis. CT specimens were made from a welded plate with notches at different distances from the fusion line. High fatigue crack growth rates were found along the fusion line and fusion line+2mm line into the heat affected zone.