Application of high-strength materials on trackless rubber tire vehicles (2)
2 Welding methods, materials and equipment for high-strength steel plates 2.1 Welding methods and materials Table 4 % of deposited metal chemical composition Table 5 Mechanical properties of deposited metal
The welding method is flux cored wire CO 2 arc welding. The welding materials were made by Lincoln, Inc., Outershield 71M (1.2) and Outershield 70 (φ2.4) flux-cored wire. The former is used for the welding of tack welds and small weld beads (δ ≤ 10 mm). These two flux-cored welding wires are low-hydrogen series flux-cored welding wires which can obtain high strength and good impact toughness, and have the characteristics of good welding quality, less spatter, easy slag removal, beautiful appearance and high welding efficiency. Widely used in the welding of various low carbon steels and low alloy steels.
The chemical composition and mechanical properties of Outershield71M and Outershield70 wire are shown in Table 4 and Table 5. Wire type Protective gas ω(C) ω(Mn) ω(Si) ω(P) ω(S) Outershield70 CO 2 0.084 1.4 0.75 0.99 0.011 Outershield71M CO 2 0.05 1.3 0.65 0.005 0.007 Wire type Protective gas σ b
/MPa σ s
/MPa δ A
/% A kv
/J Outershield70 CO 2 570~655 480～570 22~29 34～95 Outershield71M CO 2 540～585 470～540 25~30 34～135
It adopts DC-400, DC-600 power supply, LN-9 wire feeder, welding torch and shielding gas device of Lincoln Company of the United States.
3 Development of welding process
(1) Preheating. Pre-weld preheating can slow down the cooling rate of welded joints, prevent the formation of hardened structures, and reduce the tendency of cold cracking. But the main problem is how to choose a reasonable preheating temperature and the lowest interlayer temperature according to the chemical composition of the steel, the thickness of the material and the degree of constraint of the connection. Through the test, it can be concluded that the preheating temperature of the steel plate with the thickness of 12mm or less is (100±10) °C, and the preheating temperature of the steel plate with the thickness of more than 16mm is (200±10). ° ° is appropriate.
(2) After the heat. For parts with a thickness of 12mm and more than 12mm, in order to avoid the occurrence of transverse cracks in the multi-layer weld, and also to prevent cracks caused by insufficient preheating before welding, the welding should be carried out immediately after heating and tempering. Stress treatment to eliminate welding stress between the weld and the base metal joint. The tempering temperature should be maintained at around 350 °C.
(3) DC reverse connection method. In order to increase the penetration and avoid defects in the fusion zone, the power supply adopts a DC reverse polarity connection method.
(4) Welding parameters. The selection of welding parameters is shown in Table 6. Welding materials Wire specification Welder model Welding current / A Welding voltage / V Wire feed speed / m . Min -1 Gas flow rate / L. Min -1 Outershield
71M Φ 1.2 DC-
400 140～
180 26~
29 6.5~
8 10~15 Outershield
70 Φ 2.4 DC-
600 300~
400 28~
32 3 to 5 15~
20
4 welding
(1) Preheating the thick plate connecting bead of δ≥12mm with oxyacetylene flame and measuring with the temperature pen to ensure the preheating temperature requirement;
(2) The welding should be carried out continuously and cannot be stopped in the middle to ensure that the interlayer temperature is higher than the preheating temperature;
(3) Welding tooling should be used, such as using the technical shaft to ensure the coaxiality and parallelism between the structural members, and using multiple techniques to control the deformation;
(4) During the welding process, check the dimensions in all directions at any time to control and correct the deformation in time;
(5) After each layer (dao), the slag should be thoroughly cleaned after welding. Any defects should be removed in time by using the grinder, and the repair welding should be carried out.
(6) Immediately after welding, the thick plate connecting bead of δ≥12mm and the vicinity are heated to 350 °C for tempering and stress treatment, and slowly cooled to room temperature;
(7) After the welding is completed for 24 hours, the process shaft and the process lacing are removed, and then machined after natural aging to facilitate stress release.
(1) High-strength steel plate EEMS10072 has high strength, good weldability, rolling property and good impact toughness, especially with good low temperature toughness. Therefore, it is feasible for the steel plate to be used in a downhole trackless rubber wheel frame to meet the expected design requirements.
(2) 2 CO.'s flux cored arc welding, one low cost; the second is to improve the quality of welding, molding appearance, to avoid porosity, defects such as slag; third is to improve efficiency, the preheating, welding, heat treatment can Finished at once.
Author unit : Taiyuan Branch of Coal Science Research Institute
2 Zhou Zhenfeng, Zhang Wenzhao. Welding Metallurgy and Metal Weldability. Beijing: Mechanical Industry Press, 1988
3 National Machinery Industry Committee, ed. Welding joint test method. Beijing: Mechanical Industry Press, 1991
4 Tianjin Engineering Machinery Research Institute. Engineering Machinery. Beijing: Mechanical Industry Press, 1993