Laser and Hybrid Laser-Arc Welding of High Strength Steel N-A-XTRA-70

Abstract

The advantages of laser and hybrid laser-arc welding in production of welded structures from high strength steels are increase of efficiency due to rise of the welding rate by order; significant (3 – 5 times) decrease of heat input; reduction of weld size; receiving of fine grain structures in the welds and the heat affected zone increasing strength of the joint and reducing susceptibility to crack formation. Research of the peculiarities of laser and hybrid processes, their effect on weld formation, revealing the advantages and eliminating the disadvantages of laser and arc constituents of the heat sources are currently the main problems for the production engineers and researchers. Therefore, the aim of the investigation lies in determination of the effect of process mode parameters of the hybrid laser-arc and laser welding in high-strength steel welding on formation of the structure of the welded joint metal as well as the analysis of effect of this structure on their mechanical properties. The investigation was focused on the high-strength steel N-A-XTRA-70 which is widely used in European Union countries for manufacture of critical structures of different designations. A laboratory bench was developed for experiments. It was used for carrying out investigation on the process flow sheet which provided location of a consumable electrode arc at some distance ahead of a laser beam during welding proceeding. The laser irradiation source was Nd:YAG-laser DY 044 of ROFIN company (Germany). For the first time the results of carried investigations allowed determining the process modes of laser and hybrid laser-arc welding for producing quality and sound welded joints of the high-strength steel from the point of view of the structure formation and metal phase composition providing high indices of mechanical properties and crack resistance of the welded joints.

Review of scientific works dedicated to study of influence of component processes of laser and hybrid laser-arc welding on formation of structure and level of mechanical characteristics of welded joints of structural steels

“…Ці лазери забезпечують потужність випромінювання до декількох десятків кіловат в поєднанні з дуже високою якістю пучка (ВPP 8 мм×мрад до 11 мм×мрад), у порівнянні зі звичайними системами (CO2, Nd:YAG) високий електричний ККД (25-30 %) 1 . Це дозволило внести значний вклад у підвищення продуктивності виробництва товстостінних конструкцій 2 , звести до мінімуму додаткову обробку 3 та відкрити нові перспективи для різних галузей, де використовуються зварювання, і в яких до цього часу не знайшло своє застосування лазерне зварювання. Ці лазери на сьогоднішній день знайшли своє застосування у виробництвах, які вже мають досвід роботи із лазерним зварюванням високоміцних сталей, наприклад у суднобудуванні 4 .…”

Structure and Crack Resistance of N-A-XTRA-70 Steel Joints Manufactured by Hybrid Laser-Arc Welding

“…They are used in critical designation structures (arms of cranes, concrete mixers, high-pressure pipelines, offshore structures etc.) [1][2][3][4][5][6][7][8][9]. Particular attention in manufacture of such metal structures is given to production of the quality welded joints as well as providing safety and service life of these structures under extreme operation conditions [4][5][6][7].…”

“…[1][2][3][4][5][6][7][8][9]. Particular attention in manufacture of such metal structures is given to production of the quality welded joints as well as providing safety and service life of these structures under extreme operation conditions [4][5][6][7].…”