1.(1). 15crmo alloy steel pipe : steel-based pearlite structure heat-resistant steel, which has high heat strength (δb≥440MPa) and oxidation resistance at high temperature, and has certain resistance to hydrogen corrosion. Due to the high content of Cr, C and other alloying elements in the steel, the hardening tendency of the steel is obvious and the weldability is poor.
2. Welding materials: According to the working characteristics of the welding properties of 15CrMo steel, according to the previous experience, we have selected two schemes for the welding test with reference to the welding card provided by foreign countries. Option I: welding preheating, using ER80S-B2L welding wire, T1G welding base, E8018-B2 welding rod, electrode arc welding cover, local heat treatment after welding. Scheme II: ER80S-B2L welding wire, T1G welding base, E309Mo-16 welding rod, welding rod filling arc welding cover surface, no heat treatment after welding.
3.15CrMo steel thick-wall high-pressure pipe welding uses two welding schemes:
(1). Scheme I 550/530 Base metal 50. Qualified 84.8 162 135.6
Option II 525/520 base metal 50. Qualified 79.4 109.2 96.7
It can be seen from the tensile test results that the tensile specimens of the two schemes are all broken in the base metal, indicating that the tensile strength of the weld is higher than that of the base material; the bending test is all qualified, indicating that the weld has good plasticity. According to the impact toughness test results in Table 5, the impact toughness of the scheme I is significantly higher than that of the scheme II, which proves that the post-weld heat treatment specification of the scheme I is ideal, and the high-temperature tempering not only achieves the purpose of improving the joint structure and performance, but also makes the toughness The strength is matched properly. From the results of mechanical properties at room temperature, the two recommended welding process solutions can be used for on-site construction. Scheme I uses an electrode that is close to the base metal component. The weld bead performance is matched with the parent metal. The weld seam should have high heat strength, and the weld seam is not easy to be destroyed after long-term use at high temperature. The difficulty is that the post-weld heat treatment specification is stricter, and the tempering temperature and holding time and improper heating and cooling speed control may cause the weld bead performance to decrease. Scheme II uses austenitic stainless steel welding rods. Although the post-weld heat treatment can be omitted, due to the different expansion coefficients of the weld and the base metal, carbon diffusion and migration can occur during long-term high-temperature operation, which easily leads to welds in the fusion zone. Destruction occurred. Therefore, from the perspective of reliability of use, it is more stable to use the scheme I in the field.
4.15CrMo steel thick-wall high-pressure pipe welding is feasible by using two welding schemes. In order to ensure that the weld bead performance is matched with the base metal and has high heat strength, the effect of the scheme I is better, and the key is to use it carefully when the heat treatment cannot be performed.
Alloy Barrel Screw,Bimetallic Screw And Barrel,Bimetallic Alloy Barrel Screw,Bimetallic Twin Screw And Barrel
Zhoushan Jinmao Machinery Manufacturing Factory , https://www.jinmao-machinery.com