| To research the quality of SWRCH35K cold-heading steel in Xunhua Iron and Steel Co.Ltd, the macro-inclusions and micro-inclusions are observed by the means of on-site systemic sampling and testing detection. Inclusions are further analysed by SEM/EDS. The amount, dimension, distribution, and contents variation of T[O] and N are studied during the production process. To investigate the cracking reasons, the effects such as inclusions, surface quality, metallographlic structure of cold-heading samples and wire rod samples are studied.It is found that: The contents of T[O] and N in billet are 41×10-6 and 68.67×10-6 in average; The macro-inclusion is 105.33mg/10kg, It is mainly multiplicity of silicate; the amount of micro-inclusion is reduced dramatically after LF process. The results show that: The refining of LF is effective on removing inclusions and the amount of inclusions is higer in the tudish than that after LF process. The reason is that: first, the carbonized rice-hull has only adiabatic function but can not prevent reoxidation and absorbing inclusions in the tudish; secondary, the extended nozzle without argon gas seal absorbs air. The elements of Ti, Zn, Na, and Ka in billet come from the mould flux. It indicates that the entrapment is in mould; the amount variation of micro-inclusion is consistent with the content of T[O] in every site; the surface fold of wire rod is the main reason of crack and the metallographic structure is made up of ferrite and perlite. The ferrite content is about 30%~50% in the lumpish shape and no bainite no marstensite are found in the wire rod. The grain size of wire rod is about 9.0~10.0. This will make the tensile strength increase, and impair the cold-heading performance. Although the inclusion is not the cracking reason, the high level amount of inclusions will restrict the improving of cold-heading performance. Chelorine is found in the inclusion of steel. Chelorine's source and effect on the smelt precess are analysed.
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