Hirohisa Watanabe

Guidelines for Repair Welding of Pressure Equipment in Refineries and Chemical Plants

This paper outlines the technical logic/steps that have been documented in JWES-CP-0902, “Guidelines for Repair Welding on Pressure Equipment”(hereinafter the Guidelines). The paper covers the work flow logic that can be followed by maintenance personnel as they address making a repair welding in pressure vessels/piping made of both ferrous and nonferrous materials after flaw detection during inspection during refinery operation. Material degradation factors that are considered include: strength loss, ductility loss, temper embrittlement, σ embrittlement, corrosion metal loss, stress corrosion cracking, fatigue, and creep.

Load-carrying capacity of overmatched welded joint of stainless steel for building structure

A finite element (FE) analysis of tensile test for a welded joint of austenitic stainless steel for a building structure SUS304A predicts necking in the weld metal as well as lower tensile strength than that of the base metal, even though the joints has the strength-overmatched weld metal. The FE analytical studies also suggest that such an anticipated deformation behavior comes from large difference in uniform elongation between the base metal and the weld metal. Experimental works for overmatched welded joints using SUS 304A and welding wire TS308MoJ supports the joint strength and the necking behavior demonstrated by the FE analysis. On the basis of parametric FE analyses, mechanical parameters that should be controlled to ensure the base metal necking and the tensile strength of a base metal in tensile test of the overmatched joint are proposed.

Guideline for Repair Welding of Pressure Equipment in Refineries and Chemical Plants: Part 5—Repair Welding for Specific Materials - Heat Resistance Alloy and Non-Ferrous Metals

It has been recognized that repair welding takes an important role in the long term, safe operation of pressure equipment. Responding to the needs in petroleum and chemical industries, the Japan Welding Engineering Society (JWES) published Guideline for repair welding of pressure equipment at 2009. This paper describes the key points of repair welding for heat resistance alloy and non-ferrous metals such as Nickel, Copper, Titanium and their alloys, based on JWES’s guidelines. Before implementing repair welding, it is important to understand the features of damaged materials, because these materials have been used at severe environment in plants.Copyright

Effect of Transformation Temperature of Weld Metal on Welding Distortion

Welding distortion during welding is an inevitable outcome of weld metal shrinkage due to non-uniform heating and cooling in welded joints. Several studies have investigated methods of estimating and controlling welding distortion in order to construct steel structures correctly, easily and efficiently. In the present study, the effect of transformation expansion of the weld metal on welding distortion was investigated in order to develop a welding wire that reduces welding distortion. Concretely, experiments and numerical simulations were performed on the effect of the transformation temperature of the weld metal on angular distortion of a horizontal fillet welded joint. The results showed that angular distortion of the welded joint decreases when the martensitic transformation start temperature of the weld metal decreases in the range from 350°C to 450°C. Based on this result, a welding wire that is effective in reducing welding angular distortion was developed considering usability, weldability and the mechanical properties of welded joints.Copyright