Research on Microstructure Refinement Technology of A36 Ship Plate Steel

Taking A36 ship plate steel as the research object, the austenite recrystallization behavior in the hot deformation process was studied, and the austenite recrystallization transformation law of the steel in the hot deformation process was mastered. In order to improve and stabilize the process, formulate Reasonable controlled rolling and controlled cooling process lays the foundation.

1 Experimental materials and methods
The experimental material is a 252mm thick A36 ship plate steel continuous casting slab produced by a factory, and its chemical composition is shown in Table 1 . A cylindrical sample of quasi 8mm x 15mm is processed from the billet sample with a molybdenum wire cutting machine . Single-pass and double-pass compression tests were carried out on the Gleeble-1500D thermal simulation testing machine.

Table 1 Chemical composition of experimental steel A36 ( mass fraction , % ) Tab.1 Chemical composition of experimental steel (wt, % )

C	Si	mn	P	S	No	V	You
0.07	0.25	1.5	0.015	0.005	0.045	0.06	0.01

Figure 1 shows the experimental schemes of single-pass and double-pass compression respectively. Figure 1(a) is heated to the austenitization temperature of 1180 °C at a heating rate of 10 °C/s and kept for 180 s ; then cooled to the deformation temperature T1 at a speed of 5 °C/s , and the single-pass deformation temperatures T1 are respectively 850 , 900 , 950 , 1000 and 1050 ° C , the deformation amount is 70 % , the deformation speed is 5 s - 1 , and then cooled to room temperature in air to measure the deformation resistance curves of the experimental steel at different deformation temperatures. At the same time , the static recrystallization law of A 36 ship plate steel was determined by constant temperature double-pass compression experiment .

• When the deformation temperature of A36 experimental steel is above 975 °C , recrystallization occurs relatively completely; while below 890 °C , almost no recrystallization occurs.
• In the final rolling in the partly recrystallized zone, relatively fine ferrite grains can also be obtained through reasonable deformation and temperature control, and relatively fine acicular ferrite can be obtained through deformation at a higher final rolling temperature.

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