This document provides a Japanese grouping system for materials for welding purposes, classified in accordance with the grouping system of ISO/TR 15608. It can also apply for other purposes, such as heat treatment, forming, and non-destructive testing. Types of steels are listed in accordance with the grouping system of ISO/TR 15608:2017, Table 1. Types of aluminium and aluminium alloys are listed in accordance with the grouping system of ISO/TR 15608:2017, Table 2. Types of titanium and titanium alloys are listed in accordance with the grouping system of ISO/TR 15608:2017, Table 5. This document covers grouping systems for the following standardized materials: — steels; — aluminium and its alloys; — titanium and its alloys.