Welding and Grinding of Office Chairs

Welding and grinding office chairs should be carried out in accordance with standardized procedures to ensure structural stability and surface smoothness. The specific steps and key points are as follows:

I. Welding Process

1. Material Preparation

   • Square Tube Selection: Use 20×40mm galvanized or carbon steel square tubes with a thickness of ≥1.5mm for chair legs; 30×50mm square tubes for the seat frame; and adjust the dimensions of the backrest frame according to the design.
   • Tool Preparation: Prepare a 220V electric welder, angle grinder, E4303 welding rods, tape measure, marking pen, wire brush, protective face shield, insulating gloves, and non-slip welding table.
   • Cutting and Blanking: Cut the square tubes according to the design dimensions. The chair legs should be 40-45cm long, the seat frame should be 35-40cm long and 30-35cm wide, and mark the cutting points on the backrest while reserving a tilt arc.

2. Frame Assembly and Positioning

   • Seat Base: Weld four short square tubes into a rectangular frame and add 2-3 horizontal reinforcing ribs inside to enhance load-bearing capacity.
   • Installing Chair Legs: Vertically weld the chair legs at the four corners of the seat frame. Use a square ruler to calibrate the perpendicularity and ensure that the heights of the four legs are consistent.
   • Welding the Backrest: Bend the backrest square tube to form an arc (or install it at an incline) and weld it to the rear side of the seat frame, reserving a 10-15cm tilt angle to improve comfort.

3. Key Points of Welding Operation

   • Cleaning Treatment: Use a wire brush to clean rust and oil stains from the welding area to ensure a flat contact surface.
   • Welding Parameters: Adopt a flat welding position with a current of 80-120A (adjust according to the thickness of the square tube). Keep the welding rod at a 30-45 degree angle to the welding surface.
   • Quality Inspection: The weld seam should be continuous and full, avoiding slag inclusions and porosity. After welding, gently tap off the welding slag and inspect the welding quality.
   • Safety Protection: Wear a protective face shield and insulating gloves throughout the process to prevent arc burns to the skin or eyes.

II. Grinding Process

1. Grinding and Trimming

   • Rough Grinding: Use an angle grinder with 80-grit sandpaper to grind the weld points, removing welding slag and protrusions.
   • Fine Grinding: Switch to 200-grit sandpaper for fine grinding to ensure a smooth surface without scratches.
   • Structural Inspection: Check if the frame is loose or deformed, and re-spot weld and correct any offset positions.

2. Cleaning and Surface Treatment

   • Cleaning: Remove oil stains and rust from the frame surface. Carbon steel materials need to be brushed with an anti-rust primer in advance.
   • Coating: Galvanized square tubes can be directly brushed with clear varnish for rust prevention; carbon steel square tubes need to be brushed with 2 coats of anti-rust paint + 1 coat of topcoat to enhance corrosion resistance.

III. Safety Precautions

1. Maintain good ventilation during welding to avoid inhaling fumes.
2. Do not operate on wet ground to prevent electric shock.
3. After welding, wait for the weld seam to cool completely before touching the finished product to avoid burns.