Effect Of Feeding Ca-Mg-RE-Zr Composite Cored Wire During Refining Of Liquid Steel On Abrasive Wear Resistance And Weldability Of High-strength Steels

Feeding micro-additives is a generally accepted method in iron and steel making industry toimprove the quality of steels. In the present work, two kinds of high-strength low-alloy wearresistant steels which were produced on an industrial scale were investigated. Steel1contained0.31(wt.%) Ni. It was produced by the conventional processing. Steel2did not contain Ni.However, it was treated by feeding Ca-Mg-RE-Zr (RE, Rare Earth) composite cored wire (1.5kg/t) during the refining of liquid steel.The abrasive wear performance and weldability of the two kinds of high-strength low-alloywear resistant steels were evaluated by laboratory wear tests (sliding abrasive test and stirringwear test) and gas shielded arc welding test. Optical microscopy and scanning electronmicroscopy were utilized to observe the worn surfaces, microstructures, inclusions and fracturemorphologies.The tested results showed that the basic microstructure of the investigated steels wastempered martensite. The mechanical properties such as tensile strength, hardness and impacttoughness of Steel2was better than that of Steel1. A small amount of Ca-Mg-RE-Zr compositecored wire feeding replaced0.31(wt.%) of expensive Ni resulted in better mechanicalproperties.The wear performance of Steel2treated by the feeding of composite cored wire was betterthan that of Steel1, both in the stirring wear test and the sliding abrasion test. Microcutting,microploughing and scratching were the main wear mechanisms in the abrasive wear tests. Theabrasive loss was larger in the wet wear condition than in the dry wear condition in slidingabrasion tests because of the increase in corrosion wear and the decrease in debris accumulation.Feeding Ca-Mg-RE-Zr composite cored wire into the liquid steel replaced0.31(wt.%) ofexpensive Ni improve the elongation of the welding joint and the toughness of the CGHAZ forhigh-strength low alloy wear resistant steels. The microstructure in FGHAZ of Steel1is granularbainite while that of Steel2is complex microstructure, consisting of quasi-polygonal ferrite (QF),polygonal ferrite (PF) and a small amount of granular bainite (GB) and acicular ferrite (AF).The enhanced properties in Steel2which was treated by the feeding of Ca-Mg-RE-Zrcomposite cored wire into the liquid steel, including mechanical properties, wear performanceand weldability are attributed to the modification of inclusions, inclusion-induced formation ofacicular ferrite and grain refinement caused by the pinning effect of small dispersed compositeinclusions.