Refinement of packet size in low carbon bainitic steel by special thermo-mechanical control process

Chengjia Shang;Xuemin Wang;Shanwu Yang;Xinlai He Materials Science and Engineering School, University of Science and Technology Beijing, Beijing 100083, China

摘 要：<正> The packet size of bainitic steel can be refined by a special relaxation -precipitation-control phase transformation （RPC）technology. When processed by RPC process, the low carbon bainitic steel composes of two kinds of main intermediate transforma-tion phases. One is ultra-fine lath-like bainitic ferrite and the lath is less than 1μm in width and about 6μm in length, the alignmentof laths forms a refined packet, and the size of packets is about 5-7μm in length and about 3-4μm in width. The other is acicularstructure. The morphology and distribution of these acicular structures are influenced by relaxation process, the thin and short acicu-lar structures cut the prior austenite grain and refine the bainitic packet size. For the optimum relaxation time, the packet size can berefined to the finest. The mechanical properties are influenced by relaxation time and the 800 MPa grade low carbon bainitic steelwith excellent toughness can be obtained by RPC process.

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