Influences Of Residual Elements On Mechanical And Property Of SPHC Steel Strip

SPHC hot-rolled steel strip with good stamping performance, mainly used for automobile andhome appliance industry. In SPHC hot-rolled strip steel smelting process, some impurities elements willeventually residues in the steel. Residual elements mainly come from the ore and scrap steel. And theexistence of residual elements is one of the main factors of steel quality is not stable.The influences ofCr, Ni and Cu content on the micro-structures and properties of SPHC hot-rolled strip steel of tensilestrength, hardness, change trend and the regularity of residual elements segregation in the form oforganization were studied by means of tensile testing machine, hardness tester, metallographicmicroscope and SEM. The result shows that:1) SPHC hot-rolled strip steel mainly composed of ferrite and pearlite. SPHC hot-rolled strip steeltensile strength was almost unchanged with the increase of Cr element content; Yield strength showed atrend of gradually decline; The ratio of yield strength and tensile strength showed a trend of gradualdecline; The hardness showed a trend of first increases and then decline. Cr element to add can improvethe strain hardening index of material. Cu in the grain boundary precipitation decreased SPHC hot-rolled strip steel tensile and yield performance. Cr in the grain boundary precipitation decreased SPHChot-rolled strip steel toughness.2) The tensile strength of samples are rising with the increase of cold rolled down rate. When theunder pressure ratio is greater than70%, strain hardening index of Strip steel is increased moreobviously. Precipitation amount of Cr, Ni and Cu is increased with SPHC hot-rolled strip cold rollingprocess Precipitation amount of Cr, Ni and Cu will increase metal storage energy, make the strip steelappear "hard" phenomenon; Maximum difference of tensile strength is increased with the increase ofdifference of precipitation amount of element content. With the control of residual elements equivalentunder0.05%, reduce Cu content in the steel, can reduce the effect on the properties of steel.3) SPHC cold-rolled annealing strip steel mainly composed of ferrite, pearlite and a large numberof cementite. The grain size are basically similarity. When there is residual elements, the SPHC cold-rolled strip steel can improve mechanical properties by slowly heated to700℃, holding4h.