Junior Beam / JIS I-Beam

Overview of Junior Beam / JIS I-Beam

Junior Beam, also known as JIS I-Beam or Japanese Standard I-Beam, is a hot-rolled structural steel section produced according to JIS G3192 standard in Japan and widely adopted across Asian markets including Southeast Asia, the Middle East, and Africa. Junior Beams are characterized by their I-shaped cross-section with tapered flanges, and they are defined by section height and mass per metre following the Japanese Industrial Standard (JIS) section designation system. Common designations include 100×50, 125×65, 150×75, 175×90, 200×100, 250×125, 300×150, 350×150, 400×150, and 450×150.

Junior Beams are widely used in light to medium structural applications including small building frames, machinery supports, conveyor structures, mezzanine platforms, agricultural buildings, industrial shelving systems, and general fabrication. They are one of the most economical I-section profiles available and are commonly supplied in SS400 and SM490 steel grades per JIS G3101 and JIS G3106 standards, as well as equivalent grades Q235B and Q345B under Chinese GB standards. Their lightweight section proportions, economical production cost, and ready availability in Asian markets make Junior Beams a popular choice for cost-effective structural and industrial applications.

Key Features and Manufacturing Process

Junior Beams are manufactured through the hot rolling process, where heated steel billets are passed through section rolling mills with paired rolls that form the I-shaped profile with tapered flanges in a series of rolling passes. The tapered flange geometry of JIS I-beams results in flanges that are thicker at the web root and taper toward the flange tips, following the dimensional standards specified in JIS G3192. Section dimensions are tightly controlled including section height, flange width, web thickness, flange thickness, and root radius.

Junior Beams are available in a compact section range from 100mm to 450mm section height, with mass per metre ranging from approximately 9 kg/m for the lightest section to 92 kg/m for the heaviest. Standard steel grades are SS400 (yield ≥245 MPa, tensile 400-510 MPa) and SM490 (yield ≥325 MPa, tensile 490-610 MPa) per JIS standards, with equivalent Chinese grades Q235B and Q345B also commonly available. Standard lengths are 6m and 12m with cut-to-length service for project requirements. Surface treatment options include bare mill surface, shot blasting, red primer painting, hot-dip galvanizing, and anti-rust oil coating.

Main Applications of Junior Beam / JIS I-Beam

Junior Beams are widely used across light to medium structural and industrial applications in Asian and international markets. In building and construction applications, they are commonly specified for small steel frame buildings, light industrial workshops, residential steel structures, agricultural and greenhouse structures, prefabricated building frames, mezzanine floor systems, platform supports, staircase structures, and general steelwork where economical section profiles are required.

In industrial and infrastructure applications, Junior Beams are used for conveyor support structures, machine bases and equipment frames, shelter and canopy supports, cable tray systems, storage rack structures, fence posts and railings, mining and quarry equipment frames, small bridge structures, pier and dock supports, railway platform minor structures, shipyard auxiliary structures, and general fabrication projects across manufacturing, logistics, and construction sectors. Their economical cost, lightweight handling, and compatibility with common welding and bolting methods make Junior Beams a practical choice for a wide range of load-bearing and framework applications.

Why Choose Us for Junior Beam / JIS I-Beam

Shandong Tanglu Metal Material Co., Ltd. supplies high-quality Junior Beam and JIS I-Beam steel sections for construction, industrial, and general fabrication applications in Asian and global markets. We provide a complete range from 100×50 to 450×150 sections in SS400, SM490, Q235B, and Q345B steel grades with stable dimensional control, verified mechanical properties, and consistent surface quality.

Every shipment can be supplied with mill test certificate, certificate of origin, and third-party inspection documentation as required. Surface treatment options including shot blasting to Sa2.5, red primer painting, and hot-dip galvanizing are available for corrosion protection requirements. We support standard lengths, cut-to-length service, and professional export packaging for container and break-bulk loading. With competitive pricing, fast quotation response, and reliable supply for both small and large orders, we are a dependable partner for distributors, fabricators, and project contractors sourcing JIS I-Beam sections for domestic and export use.