Under the background of advocating low-carbon, energy conservation and environmental protection, all kinds of transportation machinery are also developing in the direction of lightweight. In this paper, the mature TRIP steel production technology is applied to the production of steel pipe, and the thin-walled TRIP steel seamless pipe with ferrite, bainite, residual austenite and a small amount of martensite is successfully produced. Its mechanical properties and internal high pressure forming properties are experimentally studied by means of ordinary tension, pipe end flared, annular tension and hydraulic free expansion, The effects of heat treatment process on microstructure, mechanical properties and internal high pressure forming properties of TRIP steel alloy seamless pipe were analyzed. The main innovative achievements are as follows:
(1) TRIP steel thin-walled seamless tubes with chemical compositions of A, B, C, D, E and F were successfully produced by smelting forging piercing cold drawing heat treatment process.
(2) The effect of heat treatment process on Microstructure and mechanical properties of TRIP steel seamless pipe was studied.
(3) The hydroforming performance of TRIP steel seamless tube was studied by tube end flaring test, and the effects of conical tool tip angle and heat treatment process on flaring were analyzed.
(4) A method for determining the material constant in Oyane ductile fracture criterion by tube end flaring test is proposed, and the universal applicability of this method is verified by using two different materials of TRIP steel seamless pipe and carbon steel seamless pipe.
(5) An annular tensile test device is designed. According to the characteristics of the test device, a method to determine the circumferential stress, strain and plastic strain ratio (CR value) of the pipe is proposed, and the feasibility of this method is verified by FEM numerical simulation.
(6) The circumferential mechanical properties of TRIP steel seamless tubes a, B, e and F were studied by ring tensile test, and the effect of heat treatment process on the circumferential mechanical properties of TRIP steel seamless tubes was analyzed.
(7) The hydraulic free expansion test device is designed, the method of determining the equivalent stress first-order effect curve of pipe by hydraulic free expansion test is proposed, and the effects of deformation rate and heat treatment process on large internal pressure and large expansion height are analyzed.