Crack resistance analysis of new wear-resistant steel NM400 oblique Y-shaped groove welding
1 experimental materials
NM400 wear-resistant steel plates with a thickness of 8mm were used in this experiment and Y-shaped groove welding was adopted. The inclination angle of the oblique Y-shaped groove was 30°, 45° and 60° respectively, and the welding process parameters of single-layer manual welding and double-layer manual welding were determined (see Table 1).
Table 1 welding process parameters of automatic welding
2 Experimental process
(1) The Y-shaped groove machining was carried out by CNC machine tool, and the inclination angle of inclined Y-shaped groove was 30°, 45° and 60° respectively.
(2) The welding of the oblique Y-shaped groove by the welders took another day, Step 1 single-layer manual welding and Step 2 double-layer manual welding.
(3) After the welding is completed, the specimens were put in an atmosphere furnace at 750℃ for 1 hour and then cooled naturally, and the specimens were heat treated to simulate the annealing heat treatment process.
(4) The specimens were subjected to tensile test. And three kinds of different inclination angle specimens were tested separately.
3 Test results
The test results are shown in Table 2.
Table 2 shows that for the two welding processes, the tensile strength of the single-layer welded specimens with different inclination angles of Y-shaped groove decreases with the increase of the inclination angle, and the tensile strength of the single-layer welded specimen with an inclination angle of 30° is higher than that of the double-layer welded specimens with an inclination angle of 30° and 45°. The tensile strength decreases with the increase of the inclination angle, and the tensile strength of the specimens with an inclination angle of 60° decreases more significantly, which affects the standard strength of the welded joint. The result shows that when the inclination angle increases, the crack resistance of the Y-shaped groove weld of NM400 wear-resistant steel decreases.
Shows the comparison of the stress distribution curves of NM400 wear-resistant steel Y-shaped groove weld specimens with different inclination angles. With the decrease of the inclination angle from 60° to 30°, the stress distribution in each span of the specimen shows a maximum stress, indicating that the weld is more prone to fracture. There is no obvious fracture point at 30°, indicating that the weld is more reliable at this inclination angle. With the increase of the inclination angle, the maximum peak value of the stress curve gradually increases, the maximum stress point gradually approaches the end of the weldment and the stress concentration increases, which is beneficial for the occurrence of crack.
4 Conclusion
By comparing the test results and analyzing the stress distributions of the welded joint, it is concluded that the NM400 wear-resistant steel welded joint of oblique Y-shaped groove has good crack resistance when the inclination angle is less than 45°. With the increase of the inclination angle, the tensile strength and crack resistance of the specimen tend to decrease. Therefore, it is necessary to select the appropriate inclination angle to determine the tensile strength of the welded joint in practical applications, so as to ensure the reliable crack resistance of the welded joint.
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