Method for strengthening welding line by laser temperature shock free of absorption layer

Abstract

The invention discloses a method for strengthening a welding line by a laser temperature shock free of an absorption layer, and relates to the field of non-traditional machining. The method comprises the steps of: firstly, preheating a weld assembly substrate, quickening dislocation movement of a part base by temperature rise; and directly shocking the welding line by a high-energy nanosecond laser beam after the temperature of the base body is improved to dynamic strain aging temperature. Laser energy is absorbed at a metal surface to evaporate and expand, so as to form high-temperature and high-pressure plasma when laser irradiates target metal; the plasma is restricted by a constraint layer; a high-strength compact wave is generated; the strength is from a few of to dozens of GPa, and much greater than the yield strength of metal and alloy, so that a metal or alloy material in a welding line area generates severe plastic deformation; crystal particles at the surface of the welding line are fined or nanocrystallized; high residual compressive stress is induced in an impact area. Thus, the corrosion resistance and high-temperature fatigue life of the welding line are improved. The method is suitable for the fields of strengthening and life extension of a welding element which cannot be coated with the absorption layer, for example, surface strengthening of the welding part at the inner wall of a pipeline and improvement of the mechanical property. The method is a novel straightening treatment method on the welding line, and has a wide application prospect.

Description

technical field [0001] The invention relates to a welding seam strengthening technology, which is a non-absorbing layer laser temperature impact strengthening welding seam technology. Background technique [0002] The mechanical performance, fatigue performance and corrosion resistance of the welded part are very important, but the post-weld heat treatment will destroy the welding quality of the whole weld and cause high residual tensile stress, which will directly lead to the fracture failure of the welded part and improve the welding quality. A good alternative to the strength of the seam heat-affected zone is strain hardening, laser shock strengthening treatment, which can greatly improve the mechanical properties of the weld seam of the weldment. [0003] The laser absorbing layer plays an important role, first, to protect the metal surface from laser ablation and melting; second, to increase the shock wave density. When laser pulses of sufficient intensity strike a met...

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Problems solved by technology

Although laser shock strengthening is widely used in aerospace, due to the limitation of the absorbing layer, laser shock strengthening cannot be adopted in nuclear power engineering occasions such as welding the inner wall of the pipeline. In view of the above situation, in 2006, Y.Sano et al. [Materials Science and Engineering A, 2006, 417: 334–340.] Friction stir welding of A6061-T6 aluminum alloy by non-absorbing layer laser shock treatment improves the hardness and fatigue performance of welded parts, but at room temperature Laser shock refinement surface grain depth and refinement degree are not enough, the corrosion resistance of welded parts is poor and the high temperature fatigue life is short

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