| High-strength steel QD685 for shipbuilding has some characteristics including high strength and toughness, low-temperature-resistance, good impact performance and comprehensive mechanical property, stable performance of large cross-section, high hardenability and heat treated stability. It is a perfect material for making shipbuilding high-strength steel forgings, such as pipe fittings and bushings. Using high-strength steel QD685 can save ship, lower ship weight,and increase ship structural strength.In this thesis, in the view of shipbuilding, the author mainly does research on the technology of forging and heat treatment in the process of QD685 steel production. For the increasing of production efficiency, the process of forging is similar to the forging process of the original same type of high-strength steel. As to heat treatment, the author does mechanical property tests of samples which are produced in different heat treatment parameters to obtain optimum technological parameters. First test, alter temperature in a wide range and determine the temperature range of quenching and temper; second test, reduce the variation temperature range in an acceptable range and obtain optimum technological parameters; third test, verify optimum technological parameters. On the basis of all work above, the author analyzes results of mechanical property test, microscopic test and drop-weight test; discuss the influence of production technology on performance of QD685 steel; and obtain optimum technological parameters of forge work and heat treatment. The research offers some reference values about optimum technological parameters of batch production. |
