Defects And Process Optimization Of PC Steel Bar

Pre-stressed concrete used steel bar (ab. PC steel bar)is a new material used in construction. Widely used in tubular pile of bridge and high-rise building. The technique of producing PC steel bar is quenching together with tempering. But there is some problems about PC steel bar is that: easy ruptured, low strength, some time make PC steel bar useless. In this paper I investigate and research in the Changshu Longteng special steel. Find the reason by analysis the raw materials, productive process and the finish products, and try to find the way to deal with them.Research results show that the main defects of PC steel bar are delayed fracture, heterogeneity of heat treatment and unqualified straightness. Percent defective were high in the winter and summer. In the winter PC steel bar easily broken and in summer is the unqualified straightness. The main reasons are defects of raw materials, big crystal size, low strength of raw materials and so on. surface defects of materials, hydrogen brittleness,foreign nonmetallic substance in steel and low temperature brittleness。We can deal with those problems above by: 1) grain refining to improve ability to resist the hydrogen brittleness and low temperature brittleness;2)Check raw material quality strictly,main on chemical composition, surface defects, tensile strength.In this paper, we try to refining grain by circulate heat treatment. And result shows that circulate quenching is useless, and if we add a tempering process between double quenching, can effectively refining the grain size. The main reason is that the raw materials come by hot rolling. circulate quenching inherit the inhomogeneous grain size. Adding a tempering process between double quenching solve this problem well.