Reason Analysis of Fracture Delamination of Steel Tensile Specimen for A36 Ship Plate

Taking the fracture of A36 ship plate steel tensile specimen as the research object, the reasons for the formation of fracture delamination were analyzed by means of metallographic observation, scanning microstructure and energy spectrum analysis. According to the analysis , the segregation of C and Si elements in the middle of the steel plate to form a large amount of brittle banded mixed structures such as pearlite, bainite and even martensite is an important reason for the fracture delamination of the tensile specimen of the A36 ship plate.
Key words: delamination; center segregation; ship plate; tensile specimen

Analysis and research of A36 high-strength ship plate
A36 Test method for high-strength ship plate
Tensile specimens of A36 high-strength ship plate after fracture. Use a drill bit with a diameter of 0.3 mm to drill the powder from the layered part and 1/4 part of the thickness of the fracture surface of the tensile sample for chemical composition measurement.
Table 1 Chemical composition (mass * percentage) % at the delamination and 1/4 of the thickness of the tensile sample section

Location	C	Si	mn	P	S	Nb	Ti	Cr	Cu	al	sn
Delamination	0. 14	0. 401	1. 53	0.022	0.006	0. 028	0. 016	0. 018	0.032	0. 024	0.056
1/4 thickness	0. 13	0. 417	1.48	0.021	0.003	0. 024	0. 018	0.015	0.033	0. 023	0.056

of China 's shipbuilding industry , the demand for ship plates continues to increase, and the quality requirements for ship plates are also increasing Layer phenomenon occurs from time to time, which seriously affects the quality performance and delivery date of the steel plate. In this paper, scanning electron microscope observation and energy spectrum analysis are used to investigate the reasons for the formation of fracture delamination of tensile samples. The fracture samples are ultrasonically cleaned with carbon tetrachloride, and the fracture morphology of steel plates is observed and analyzed by scanning electron microscope. . Cut a metallographic sample of appropriate length from the tensile layered sample near the fracture, grind and polish it with 4% nitric acid alcohol solution to etch, use scanning electron microscope and metallographic microscope to observe and analyze the structure of the steel plate, especially near the layered layer .

C and Si elements in the middle of the A36 high- strength ship plate to form a large amount of brittle banded mixed structures such as pearlite, bainite and even martensite. This brittle banded structure is the reason for the fracture delamination of the A36 ship plate important reason.

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