Arc Welding of Specific Steels and Cast Irons

Arc Welding of High-Strength Steel
1. Types and features of high-strength steels
High-strength steel is used in a variety of steel structures such as ships, bridges, buildings,
pressure vessels, storage tanks, penstocks, pipelines, autos, and rolling stock in order to allow
the steel structures to have higher design strengths. High-strength steels have higher tensile
strengths and higher yield strengths with larger yield ratios (the ratio of yield strength to
tensile strength) than mild steel, as shown in Fig. 1.1, thereby facilitating higher design
strengths. High-strength steels can be referred to as a family of steels having yield strengths
of 275 N/mm 2 (28 kgf/mm 2 ) or higher and tensile strengths of 490 N/mm 2 (50 kgf/mm 2 ) or
higher.
Tensile strength (N/mm )
2
Yield strength (kgf/mm 2 )
Yield strength (N/mm )
2
20
Tensile strength (kgf/mm )
2
110
Fig. 1.1 — Relationship between tensile strength, yield strength, and yield
ratio of steel materials
With high-strength steels, structures can be designed to have larger scales or thinner
thicknesses due to the ability of sustaining larger applied stresses when compared with mild
steel. Table 1.1 shows how the use of high-strength steel can make steel structures thinner or
lighter. The use of HT50 steel, for example, can reduce the weight of a steel structure by 25%
in comparison with the use of mild steel under the same design stress. The weight ratios
shown in Table 1.1 are calculated in accordance with the following formula.
1-2