Fixed Office Chair Steel Tube

The key to fixed office chair steel tubes lies in reasonably designing the frame structure, selecting connection methods, and ensuring material stability. This can be elaborated on from the following aspects:

1. Frame Structure Design and Fabrication
The bottom frame of an office chair is usually formed by bending steel tubes. It is necessary to determine the seat size and support angle according to ergonomics. For example, the bending radius of the steel tube at the edge of the seat should match the curvature of the cushion to avoid stress concentration and breakage. The geometric layout of the frame directly affects stability. Common designs include:

• Triangular Support Structure: Add diagonal support steel tubes at the connection between the chair legs and the crossbeam to form a triangular load-bearing system, which can effectively disperse vertical loads and lateral impact forces.
• Crossbeam Reinforcement: Install 2-3 horizontal steel tubes in parallel below the seat to enhance the frame's torsional rigidity and prevent deformation after long-term use.
• Tube Section Selection: Square or round steel tubes are preferred. Square tubes have a larger contact area during welding, resulting in higher connection strength; round tubes are more suitable for bending processes and complex curvature designs. The wall thickness should generally be ≥2mm to withstand loads of over 100kg.

2. Connection Methods and Processes
The connection of steel tubes should be selected based on the usage scenario, either by welding or screw fixation:

• Welding Connection: Suitable for non-removable fixed structures, such as T-joints between chair legs and crossbeams. After welding, grinding should be carried out to remove burrs and welding slag to avoid scratching the cushion or the user. Advantages include strong integrity and no risk of loosening; limitations include the need for cutting and replacement during repairs, which is costly.
• Screw Connection: Suitable for adjustable structures (such as backrest height) or scenarios requiring disassembly. Anti-loosening screws (such as spring washer + nut combinations) should be used, and the tightening torque should be controlled (usually 15-20N·m) to prevent loosening due to long-term vibration. Advantages include ease of repair and component replacement; limitations include the possibility of small gaps at the connection, affecting overall rigidity.

3. Material Stability Optimization
The durability of a steel frame depends on the quality of the tubes and surface treatment:

• Tube Selection: Q235 carbon structural steel is preferred, with a yield strength of ≥235MPa, which can meet daily usage requirements. Avoid using recycled materials or tubes with uneven wall thickness to prevent local stress concentration and breakage.
• Rust Prevention Treatment: After welding, pickling and rust removal should be carried out, followed by spraying with an epoxy resin powder coating (thickness ≥60μm) or adopting an electrogalvanizing process (salt spray test ≥48 hours) to prevent rusting in humid environments.
• Load Testing: Finished products must pass static load testing (such as applying a pressure of 150kg for 24 hours) and dynamic fatigue testing (such as simulating 50,000 sit-up actions) to ensure structural safety.