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Bi G.-P.,Constant Wisdom Friendship Enterprise | Jia T.-J.,Jiangsu Hongsheng Heavy Industry Group Co. | Ji W.-L.,Jiangsu Hongsheng Heavy Industry Group Co.
Jinshu Rechuli/Heat Treatment of Metals | Year: 2011

The cause of the scab defects in the internal surface of semi-manufactured tubes and cavern defects in the tubes during rolling seamless P91 steel tubes were discussed by measure and analysis of scab and tube of P91 steel tubes. The results show that there are compound inclusions on the surface of scab defects and B-kind compound inclusions in the tubes. The compound inclusions are the main causes for producing scab and cavern defects. The compound inclusions is the reaction product of Al2O3 and Na2O-CaO-MgO, and Al2O3 inclusions are the reaction products of Al and O in the process of steel making (deoxidation with aluminium). Na 2O-CaO-MgO compound inclusions are the reaction products of Na 2O,CaO and MgO that were added in steel making furnace along with the FeNCr10-B webbite for N. Source

Bi G.,Constant Wisdom Friendship Enterprise | Ding H.,Jiangsu Hongsheng Heavy Industry Group Co. | Yao Q.,Jiangsu Hongsheng Heavy Industry Group Co. | Ji W.,Jiangsu Hongsheng Heavy Industry Group Co.
Jinshu Rechuli/Heat Treatment of Metals | Year: 2012

The formation mechanism of surface defects of cold-rolled steel strips for body of bimetal band saw blade was discussed by means of chemical analysis, SEM analysis, and X-ray analysis and so on. The results show that 1) there is a composite oxide layer mainly consisted of Fe 3O 4 on the surface of the cold-rolled steel strips. The thickness of the oxide layer is about 12 μm, and there are many cracks in the oxide layer. A part of oxide peels from the matrix and forms pitting, and another part of oxide bulges from the matrix but still connects with the matrix and forms flakes peeling. 2) There is an intermediate zone layer with the thickness of 7 μm between the composite oxide layer and matrix, and the zone is poor of Cr, Mn and C. 3) Globular carbide that generated during spheroidizing annealing mainly exists in the matrix, while a small amount in the intermediate zone, and minute quantity exists in the oxide layer. 4) The oxides layer and the intermediate zone form during spheroidizing annealing and/or hot rolling and the oxides layer is pressed and inserted into the intermediate zone during the subsequent cold rolling process. Source

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