Process Research And Product Development Of Low Alloy High Strength Steel For Cold Rolling Structure

Cold rolled high strength steel with low alloy high yield strength ration and showed good forming and welding performance,etc,than carbon structural steel has higher yield strength,and has lower cost compared with the dual phase steel high strength steel,and other advanced so highly market,widely used in automobiles,home appliances,building and other industries structure,which applied in the automotive lightweight is more outstanding,especially in the domestic independent brand cars and new energy vehicles under rapid development,cost-effective(low cost high performance)of high strength steel play an important role in cold rolled low alloy.Although cold rolled high strength steel is A low alloy high strength steel,tradition and has formed the relevant technical standards at home and abroad(such as JFS A 2001-1998,SAE J2340-1999,EN 10268,GB/T20564-2010),domestic steel companies such as baosteel,anshan iron and steel,wisco have been implemented in bulk delivery,but due to production line,the characteristics of unit equipment,product design,the production technology and product quality.In this paper,based on in xichang steel vanadium steel,steel rolling production system as well as laboratory simulation,annealing process through the composition design,laboratory research,combined with the unit equipment technical conditions,puts forward the reasonable industrial trial production plan,combined with the industrial development of smelting,hot rolling,rolling and annealing technology research,solves the fine grain structure,grain boundary cementite,performance problems,such as uniform stability control achieved 340 MPa grade cold rolled low alloy identity of"ingredients-process-the structure of the organization-performance" match,successfully developed excellent performance stability,meet the requirements of the use of user P340LA HC340LA cold rolled high strength steel,low alloy,Realize the bulk supply.The main achievements are as follows(1)combining with the characteristics of xichang steel vanadium even back line for salt bath heat treatment and laboratory results,innovative composition design,use of Nb microalloyed drag inhibition of the grain boundary ferrite and austenite grew up in the two-phase region ferrite,delaying proeutectoid ferrite formation theory,developed by the pearlite phase transformation cementite inhibition of grain boundary precipitation of control technology,formed the good performance of automobile structure with P340LA HC340LA cold rolled high strength steel,low alloy and whole process key technology,realize the stable bulk supply.(2)the mechanical properties of the product are excellent.The yield strength of P340LA controlled in the range of 40MPa(345MPa?385MPa)accounts for 96.46%,the tensile strength controlled in the range of 40MPa(450MPa?490MPa)accounts for 100%,and the elongation after fracture of A50 controlled in the range of 34%(32%?38%)accounts for 94.69%.The yield strength of HC340LA controlled in the range of 40MPa(340MPa?380MPa)was up to 95.45%,the tensile strength controlled in the range of 40MPa(455MPa?495MPa)was up to 98.93%,and the elongation distribution of A80 after fracture was 26%?33.5%,accounting for 99.64%.(3)the test steel has excellent resistance for aging and high reaming performance,which can ensure that there is no yield platform within 8 pieces under the natural aging condition,and the reaming rate is 99.1%?109.7%.(4)the products have been applied in batches to Volkswagen and other internal structural parts of passenger vehicles,which has played an important role in the optimization of product structure of panzhihua iron and steel co.,ltd.and created significant economic and social benefits.