Q235 Iron Oxide Critical Fracture Stress Research

Acid descaling method was applied in traditional cold rolling. Hydrochloricacid was inevitable to volatilize in the pickling process that could produce alarge number of pickling waste liquor, which could cause serious environmentalpollution. In June2007US TMW (The Material Works) successfully developedThe EPS (Eco Pickled Surface) new technology. Many domestic scholars havestudied the new descaling methods, but few carried on the theoretical analysisabout critical fracture stress of scale systematically. This topic focused “Q235carbon steel” as the research object and selected " Q235scale critical fracturestress research "as the research direction, mainly did the following work:1. In this paper, through study of microscopic nature of scale, variouscrystal structure in scale were introduced; the existence form of internal stress ofscale was analyzed; the characteristics of scale-matrix system was analyzed.2. Respectively from three angles of energy, crystal integrity, fracturemechanics, the critical fracture stress of scale were analyzed. From theviewpoint of fracture mechanics, the critical fracture stress formula of scale wasdeduced, which was provided reference for determination of tension in the EPSdescaling technology.3. Through finite element analysis software ANSYS/ls-dyna to simulate thefracture process of the scale, tensile stress and strain of steel plane was obtainedjust scale began to fracture.4. Before the test，scale morphology was observed by metallographicmicroscope and scanning electron microscopy (sem). After scale tensile andbending test, critical fracture stress value of scale was gained. By means ofmetallographic microscope observation on scale morphology, it contrasted thescale peeling rate and analyzed its reason.5. Finally, compared with simulation analysis and theoretical calculation toexperimental results, validity of the theoretical calculation was verified.