Performance Differences between High Frequency Welded I-Beams and Traditional Hot Rolled I-Beams

As commonly used steel products in the fields of construction and machinery manufacturing, the performance differences between high-frequency welded I-beams and traditional hot-rolled I-beams are mainly reflected in the manufacturing process, mechanical properties, specification accuracy, production cost and applicable scenarios. The following is an analysis from multiple dimensions:

1. Manufacturing process and material characteristics
High-frequency welded I-beams use high-frequency current to partially melt the steel plate and then roll it into shape. No external filler metal is required. The welding speed can reach tens of meters per minute, and the width of the heat-affected zone is controlled within 2-3 mm. This process can flexibly combine steel plates of different materials, such as composite welding of low-carbon steel and alloy steel, but the weld area is prone to hardening phases and structural stresses due to rapid cooling, and residual stresses need to be eliminated through post-weld heat treatment. In contrast, hot-rolled I-beams are formed by rolling steel billets at a high temperature of 1200℃ through multiple passes. Most of the materials are Q235B or Q355B carbon structural steels. During the rolling process, the metal grains extend along the rolling direction to form a fibrous structure. The overall residual stress level is low, but the material adjustment depends on the billet composition design, which is less flexible.

2. Mechanical properties and structural efficiency
The flange-to-web thickness ratio of high-frequency welded I-beams can reach 1:0.8-1:1.2, which has a larger section modulus than the 1:0.5-1:0.7 of hot-rolled steel. With the same cross-sectional area, its bending strength is increased by 15%-20%, and its self-weight is reduced by 10%-15%, which is suitable for large-span lightweight structures. However, there is a fusion line of 0.5-1.0 mm in the welding area, and the impact toughness is about 20% lower than that of the parent material, so ultrasonic flaw detection of the weld is required to ensure the quality. Hot-rolled I-beams achieve parallel inner and outer sides of the flanges through universal pass rolling, and the transition fillet radius between the web and the flange can reach 3-5 mm. The fatigue strength is increased by more than 30% compared with welded steel, which is more suitable for scenes such as bridge beams that bear dynamic loads.

3. Specification accuracy and production efficiency
High-frequency welding equipment can achieve continuous production of section height of 100-1000 mm and flange width of 50-400 mm, with length accuracy controlled within ±2 mm, and delivery cycle shortened by 40%-60% compared with hot rolling process. Its welding speed can reach 15-25 m/min, and the annual production capacity of a single line exceeds 300,000 tons. Hot-rolled I-beams are limited by the opening of the rolling mill. The specifications cover a height of 100-630 mm and a length tolerance of ±10 mm. Production requires 12 processes such as heating, rough rolling, finishing rolling, and cooling. The annual production capacity of a single line is about 150,000-200,000 tons, but complex section production can be achieved through universal rolling mills.

4. Cost-effectiveness and application scenarios
The raw material utilization rate of high-frequency welded I-beams is over 95%, which saves 5%-8% of steel compared with hot rolling process, and does not require processes such as roller grinding, reducing the overall cost by 10%-15%. Its lightweight characteristics reduce the cost of building foundations by 20%-30% and shorten the construction period by 30%-50%. It is suitable for large-space buildings such as steel structure workshops and exhibition centers. Although the material cost of hot-rolled I-beams is relatively high, it still has advantages in heavy machinery bases, port crane tracks and other scenes with complex loads due to its dense structure and stable performance. Its low-temperature impact energy of -40℃ can reach more than 47J, which meets the requirements for use in extremely cold areas.

5. Quality stability and testing standards
High-frequency welded I-beams must pass the GB/T 33814-2017 standard test, focusing on controlling the weld penetration (≥0.8 times the plate thickness), misalignment (≤0.5 mm) and unfused defects. Hot-rolled I-beams implement the GB/T 706-2016 standard, requiring the web wave degree to be ≤3 mm/m and the flange slope to be ≤1.5%. The performance difference between the two in seismic design is significant: due to the presence of welds, high-frequency welded steel needs to add node reinforcement plates in earthquake zones of 7 degrees and above; hot-rolled steel can directly meet the 8-degree fortification requirements through full penetration welding.

The performance difference between high-frequency welded I-beams and hot-rolled I-beams stems from their essential process characteristics. The former has advantages in lightweight and production efficiency, and is suitable for projects that are cost-sensitive and have strict construction period requirements; the latter has outstanding performance in bearing capacity and durability, and is more suitable for heavy-load and high-safety level scenarios. When designing and selecting, it is necessary to comprehensively consider the structural force characteristics, construction conditions and life cycle costs. For example, a convention and exhibition center project uses high-frequency welded I-beams to reduce steel consumption by 1,200 tons and shorten the construction period by 45 days, while the main beam of a cross-sea bridge uses hot-rolled I-beams to ensure a 50-year design life in a marine corrosion environment.