Ferritic Stainless Steel Welds Research Articles

Alloy 430 ferritic stainless steel welds fail due to stress-corrosion cracking in heat-recovery steam generator

Alloy 430 stainless steel tube-to-header welds failed in a heat recovery steam generator (HRSG) within one year of commissioning. The HRSG was in a combined cycle, gas-fired, combustion turbine electric power plant. Alloy 430, a 17% chromium (Cr) ferritic stainless steel, was selected because of its resistance to chloride and sulfuric acid dewpoint corrosion under conditions potentially present in the HRSG low-pressure feedwater economizer. Intergranular corrosion and cracking were found in the weld metal and heat-affected zones (HAZs). The hardness in these regions was up to 35 HRC, and the weld had received a postweld heat treatment (PWHT). Metallographic examination revealed that the corroded areas contained undertempered martensite. Fully tempered weld areas with a hardness of 93 HRB were not attacked. No evidence of corrosion fatigue was found. Uneven temperature control during PWHT was the most likely cause of failure.

Alloy 430 Ferritic Stainless Steel Welds Fail due to Stress-Corrosion Cracking in Heat-Recovery Steam Generator

Alloy 430 Ferritic Stainless Steel Welds Fail due to Stress-Corrosion Cracking in Heat-Recovery Steam Generator

Plasma spot welding of ferritic stainless steels

Plasma spot welding of ferritic stainless steels is studied. The study was focused on welding parameters, plasma and shielding gases and the optimum welding equipment. Plasma-spot welded overlap joints on a 0.8 mm thick ferritic stainless steel sheet were subjected to a visual examination and mechanical testing in terms of tension-shear strength. Several macro specimens were prepared. Plasma spot welding is suitable to use the same gas as shielding gas and as plasma gas, i.e., a 98 % Ar/2 % H 2 gas mixture. Tension-shear strength of plasma-spot welded joints was compared to that of resistance-spot welded joints. It was found that the resistance welded joints withstand a somewhat stronger load than the plasma welded joints due to a larger weld spot diameter of the former. Strength of both types of welded joints is approximately the same.

Welding of Heat-Resistant 20% Cr-5% Al Steels

Abstract The paper treats welding of heat-resistant ferritic stainless steels alloyed with approximately 20% Cr and 5% Al. The major part of the paper is dedicated to welding of 20%Cr-5%Al steel with 3 mm in thickness. Welding was carried out with five different welding processes, i. e., manual metal-arc, MIG, TIG, plasma arc, and laser beam welding processes, using a filler material and using no filler material, respectively. The welded joints obtained were subjected to mechanical tests and the analysis of microstructure in the weld metal and the transition zone. The investigations conducted showed that heat-resistant ferritic stainless 20% Cr-5% Al steel can be welded with fusion welding processes using a Ni-based filler material.

Explorative studies on grain refinement of ferritic stainless steel welds

Explorative studies on grain refinement of ferritic stainless steel welds

自動車排気系用フェライト系ステンレス鋼溶接ワイヤの開発

Influence of silicon and niobium on weldabilities of ferritic stainless steel welding wire have been investigated. The results are as follows. (1) At MIG and MAG welding, the weld cracking proof characteristic was improved by the addition of 1.0% silicon to weld wire and decreasing the niobium content of weld wire to 0.2%. (2) The developed weld wire with copper coating is excellent in the flatness of weld bead and the corrosion resistance.

Nitride Precipitation in Duplex Stainless Steel Weld Metal.

Duplex stainless steel base material was welded using gas tungsten arc welding with an Ar-10%H2 shielding gas and laboratory-made filler wires were employed to deposit duplex and fully ferritic weld metals having different nitrogen contents. Weld metal slow extension rate tensile (WM-SERT) testing was used to examine the hydrogen-induced cracking susceptibility and fractography of the weld metals. An increase in nitrogen content in fully ferritic stainless steel weld metal increased the density of precipitates and the hydrogen-induced cracking susceptibility. The facets on the quasi-cleavage fracture surfaces of broken WM-SERT test specimens were parallel to the {100} plane in ferrite. Scanning and transmission electron microscope observations revealed the crystallographic features and morphology of the precipitates. The precipitates were rod-like Cr2N nitrides. Many of them had directions and were parallel to the cleavage {100} plane in ferrite. An orientation relationship shown between Cr2N precipitates and ferrite suggested that the axes of the Cr2N precipitates were parallel to direction in ferrite and that they were more coherent along their long faces than at their tips. As a result, the tip of these Cr2N precipitates could act as sinks for hydrogen and may be preferential sites for initiation of hydrogen cracking; this could promote crack propagation on {001} cleavage planes in ferrite on which Cr2N precipitates are located. Higher densities of Cr2N precipitates were nucleated at solidification boundaries and at oxide inclusions in ferrite.

Ferritic Stainless Steel Welding Metallurgy

Ferritic Stainless Steel Welding Metallurgy

Heat-affected zone oxidation properties in AISI 430 ferritic stainless steel welds

High temperature corrosion of ferritic stainless steel weldments has not previously been studied. This paper is an attempt to standardize a method for assessing the oxidation properties of the heat...

8.高純度フェライト系ステンレス鋼の溶接

8.高純度フェライト系ステンレス鋼の溶接

Ductility of stabilized ferritic stainless steel welds

An investigation was made into the mechanism of ductility loss in low interstitial 18 Cr-2Mo ferritic stainless steel welds stabilized with Ti and Nb. It was found that stabilizing TiN or Nb(C,N) precipitates are dissolved during the welding process, resulting in a finer distribution of precipitates in the weld metal than in the base metal. Furthermore, the FATT was found to increase by more than 200°C, leading to decreased room temperature ductility. Such an increase in FATT may not be explained solely in terms of grain growth. Internal friction measurements indicate that no free nitrogen is present in the weld metal, yet wet chemical analysis reveals that the nitrogen is present in a soluble form. Kinetic arguments suggest that the stabilized nitrogen dissolved during welding tends to reprecipitate during solidification in the form of a chromium rich nitride phase.