What is the difference between JIS G3461 steel tube and JIS G3456 tubes?

JIS G3461 and JIS G3456 are two Japanese Industrial Standards that are frequently mentioned together in the steel pipe and tube industry, yet they serve completely different purposes. Both are carbon steel products, and both are manufactured by seamless or electric resistance welding processes, which is why buyers sometimes confuse one with the other. However, JIS G3461 covers carbon steel boiler tubing and heat exchanger tubes, while JIS G3456 covers carbon steel pipes for high temperature service. Understanding the difference between these two standards is essential when you are specifying material for a boiler, a heat exchanger, a superheater, or a high-temperature process line.

What is JIS G3461?

JIS G3461 is the Japanese Industrial Standard for carbon steel tubes used for boiler and heat exchanger service. The standard specifies seamless and electric resistance welded tubes that exchange heat between the inside and the outside of the tube, including water tubes, smoke tubes, superheater tubes, and air preheater tubes of boilers, as well as heat exchanger tubes, condenser tubes, and catalyser tubes used in the chemical and petroleum industries. It is not applicable to tubes for fired heaters or heat exchanger tubes for low temperature service.

The standard defines three main grades: STB340, STB410, and STB510. The number in each grade indicates the minimum tensile strength in N/mm². For example, STB410 has a minimum tensile strength of 410 N/mm² and a minimum yield strength of 255 N/mm². Tubes under this standard are available in hot finished or cold finished seamless forms, as well as electric resistance welded forms, and are typically supplied in smaller diameters because they are designed to fit inside boiler drums and heat exchanger shells.

What is JIS G3456?

JIS G3456 is the Japanese Industrial Standard for carbon steel pipes for high temperature service. It covers pipes used for conveying oil, gas, steam, and other fluids at operating temperatures above 350°C, typically in the range of 350°C to 650°C. Because the pipes must retain strength and resist creep at elevated temperatures, the standard requires them to be manufactured from coarse-grained killed steel by the seamless or electric resistance welding process.

The standard defines three grades: STPT370, STPT410, and STPT480. STPT480, the highest grade, must be manufactured by the seamless process only. JIS G3456 pipes are available in a wider range of outside diameters than JIS G3461 tubes, because they are used as line pipe and process piping rather than as compact heat transfer elements.

Key differences between JIS G3461 and JIS G3456

Although both standards cover carbon steel products, they differ in service type, temperature range, grade designation, size range, and testing requirements. The table below summarizes the main differences.

Chemical composition comparison

The chemical composition of the two standards is similar, but not identical. JIS G3456 grades generally allow a slightly higher carbon content because they are designed for strength retention at high temperature, while JIS G3461 grades balance strength with weldability and ductility for thin-wall heat transfer tubes. As an example, STB410 under JIS G3461 limits carbon to 0.32% maximum, silicon to 0.35% maximum, and manganese to 0.30% to 0.80%, while STPT410 under JIS G3456 limits carbon to 0.30% maximum, silicon to 0.10% to 0.35%, and manganese to 0.30% to 1.00%. Both standards hold phosphorus and sulfur to 0.035% maximum.

Mechanical properties comparison

The mechanical properties follow a similar pattern. Under JIS G3461, STB340 offers a minimum tensile strength of 340 N/mm², STB410 offers 410 N/mm², and STB510 offers 510 N/mm². Under JIS G3456, STPT370 offers a minimum tensile strength of 373 N/mm², STPT410 offers 412 N/mm², and STPT480 offers 481 N/mm². In both standards, the yield strength and elongation requirements are defined for longitudinal and transverse test pieces, and the purchaser may specify an upper limit for tensile strength where required.

How to choose between JIS G3461 and JIS G3456

The choice depends entirely on the application. If the material will be used as a heat transfer element inside a boiler, a heat exchanger, a condenser, or a superheater, then JIS G3461 is the correct standard, and grades such as STB410 are widely specified for this duty. If the material will be used as line pipe or process piping carrying high-temperature fluids, then JIS G3456 is the correct standard, and grades such as STPT410 are a common choice for steam and process lines operating above 350°C.

It is also worth remembering that these two standards are often used together in the same plant. A boiler may use JIS G3461 tubes for its water walls and superheater elements, while the steam lines leaving the boiler are made from JIS G3456 pipes. For this reason, a supplier that can provide both standards from one source simplifies procurement and keeps material certification consistent.

Where to source JIS G3461 and JIS G3456 products

EZ Steel Industrial Co., Ltd. is a manufacturer and integrated supplier of industrial metal piping systems with more than 30 years of experience since its establishment in 1994. The company supplies carbon and alloy steel pipes, stainless steel tubes, copper-nickel products, heat efficiency tubes, fittings, flanges, gaskets, fasteners, and valves for pressure service, pipeline transportation, petrochemical facilities, marine and shipbuilding systems, power plants, and heat exchangers. Its production network spans three locations, and its quality system is certified to ISO 9001, with API 5L and API 5CT product certification, PED compliance, and more than 12 quality checkpoints during production.

If you are looking for reliable boiler tubing or a trusted heat exchanger tube supplier, EZ Steel Industrial can supply JIS G3461 tubes and JIS G3456 pipes with full mill test certificates, hydrostatic testing, ultrasonic testing, and positive material identification. Contact the export team to discuss your project requirements and receive a quotation.