Welding and Joining technology group

2020.07.15 Update

The purpose of welding and joining technology group is to research and develop the welding technology and the joining technology for new materials that has developed at NIMS. Particularly, in the study of the arc welding, it is important to understand and elucidate arc welding phenomena and metal fusion behavior at high temperature and solidification behavior. In order to analyze these phenomena, we use the newest equipment and method. For example, we use the technique for directly observing welding behaviors using synchrotron X-ray imaging. Furthermore, we study a welding phenomenon and the arc phenomenon by utilizing machine learning. The machine learning method is useful to understand welding phenomena with many parameters. Using by the machine learning, the prediction of the welding condition and the estimation of properties of joints, such as joint strength and fatigue characteristics, are possible. As a new trial, we study the metal three-dimensional molding technology based on the welding technology. In addition to fusion welding research, we are also conducting non-fusion welding research, such as friction stir welding (FSW).

Specialized Research Field

1. Development of welding process and welding materials

We develop the welding process and welding materials. In recent years, Mn steel with enhanced low-cycle fatigue resistance has been developed at NIMS. In order to weld Mn steel, new welding materials and the welding process were developed. These welding materials and welding process allowed the production of the seismic damper of the welding structure. New welding process and welding consumable were applied to various buildings.

2. Application of Machine Learning for Understanding and Analysis of Welding Phenomena

Arc welding is a complex phenomenon in which four states (solid-liquid-gas-plasma) affect each other at multi-scales. Therefore, the relationship between the arc welding conditions and the characteristics of the arc weld (melting condition, joint strength, fatigue characteristics, etc.) is also complex and difficult to analyze. We are investigating the quantitative and systematic understanding of the relationship between arc welding conditions and weld characteristics, including the development of a unique machine learning technique to model the relationship in an easy-to-understand way like an experiment formula.

Input-output relation equations obtained by neural networks and the LSRF5 method (Developed method)

Penetration shape prediction of weld part by LSRF5 method

3. Advancement of Metal 3D Printing Technique based on Arc Welding

Wire and Arc Additive Manufacturing (WAAM) is a metal 3D printing technique that uses arc welding as a metal melting and solidification technique. We aim to use our knowledge of arc welding to advance WAAM. It was demonstrated that the amount of deformation of parts made by WAAM could be reduced by using the composition-controlled steel material. The material was developed to reduce the amount of deformation of arc weld joints. In addition, we are conducting research on the creation of composite steel materials with high strength and high ductility that combine high strength and high ductility steels in millimeter-scale.

Overview of WAAM technique

Effect on deformation reduction of WAAM part by use of composition controlled steel

4. Development of solid-state joining (Friction stir welding) technique

Friction stir welding (FSW) is a promising joining technique due to the potential benefits such as avoidance of crack formation and high distortion. The microstructure is generally evolved through complex processes including plastic deformation, dynamic recrystallization and grain growth because of mechanical and thermal effects. In this project, we aim to elucidate the microstructural evolution mechanism during FSW for various metals with different stacking fault energies (SFE) such as Al, Cu, brass and Ag by examining the effects of SFE, recrystallization temperature and welding conditions on the microstructure.

Grain structure development during friction stir welding.

5. In situ observation of solidification behaviors during arc welding using synchrotron X-ray

Synchrotron X-ray at SPring-8 makes it possible to directly observe the solidification behaviors of metallic alloys at a microstructural scale due to monochromatic light, high coherency and high brightness. This project focuses on the development of the technique for directly observing welding behaviors using synchrotron X-ray imaging and diffraction for various metallic alloys such as Al alloy, carbon steel and stainless steel. We also aim to elucidate the formation mechanism of solidification cracking in terms of microstructural evolution, strain/strain rate and brittle temperature range (BTR).

Schematic of experimental set-up for in situ observation during arc welding

X-ray radiographs of solidification cracking at weld crater.

6. Development of welding process of dissimilar metals

Seebeck effect is a principle of thermoelectric generation and appears at all dissimilar materials joint. But metals are expected unsuitable for thermoelectric generation because the effect is too small. In this study, we prepared large area welded joint of copper and constantan (55%Cu-45%Ni) by diffusion bonding and laser welding to overcome the disadvantage. Furthermore, we find the joints are available for thermoelectric generation. Now we are investigating advanced welding process that controls morphology and structure at welded interface for improvement of thermoelectric properties.

Thermoelectric properties of 144-pair series connected copper-constantan laser welded joint module at 900˚C

SEM composition image of copper-constantan laser welded joint and mapping images of Cu, Ni and Mn

Inquiry about this page

Welding and Joining technology Group
1-2-1 Sengen, Tsukuba-city Ibaraki 305-0047 JAPAN
E-Mail: NAKAMURA.Terumi=nims.go.jp(Please change "=" to "@")