Study on the Microstructure in Weld Metal of Cr-Ni Stainless Steel under Different Welding Technology

Abstract

According to Cr-Ni stainless steel, three different welding technology and the appropriate welding process parameters were selected. Three welded joints of Cr-Ni stainless steel were prepared. The microstructure in weld metal zone of Cr-Ni stainless steel under different welding methods was studied by X-fluorescent chemical composition analysis and microstructure analysis. The results show that alloy composition of the weld metal are different and distribute unequally under different welding methods, microstructure morphology and grain size of the weld layer are quite different. the structure of bottom is small amount of γ phase and a little δ phase are combined together and cover is γ phase and Cu-wealthy phases in the welds under TIG-MAG welding. the structure of bottom is coarse columnar crystal and cover is typical cellular dendrite in the welds under TIG- TIG welding. the structure of bottom is tiny equiaxial dendrites and columnar crystal and cover is some γ phase and a little δ phase are combined together in the welds under TIG-SMAW welding.

Study on influencing factors of f-CaO and f-MgO content in steel slag

“…The main factor restricting the large-scale recycling of steel slag is the volume expansion of steel slag, which affects the engineering quality. It is generally believed that the root cause of the poor volume stability of steel slag is the existence of f-CaO, f-MgO and RO phases, which are formed by the incomplete consumption of limestone added in the process of steel making [5][6][7] . The Ca(OH) 2 and Mg(OH) 2 crystals produced by f-CaO and f-MgO hydration reaction were locally concentrated, and the crystal volume growth rates were 92% and 148%, respectively [8,9] .…”

“…Because Mg 2+ is more tightly packed than Ca 2+ , f-CaO has the highest hydration activity among f-CaO, f-MgO and RO phase [9] . The results show that the expansion rate of steel slag aggregate is highly positively correlated with the content of f-CaO, and compared with the f-CaO inside the steel slag, the f-CaO on the surface of the steel slag is more likely to cause local expansion of the material [5,13] . Although the hydration activity of f-MgO is not as good as that of f-CaO, the influence of f-MgO on the stability of steel slag can not be underestimated because of the larger volume expansion of its hydration products and the longer hydration cycle.…”

Experimental study on resisted water pressure for connecting welds of polypropylene plastic plates in underground silos

“…However, the improved weld forms were mainly suitable for thick wall welds. Li et al [15] studied the joint forms added to the middle backing and bottom cover plates at the groove root and indicated key points that should be considered during the welding process. Wang et al [16,17] conducted a joint test and finite element analysis at the lower part of the butt weld, showing that an increased thickness of the lining plate and adoption of the surrounding weld on four sides of the lining plate protects the welding seam area.…”