The air pressure welding construction process is very important. Every detail must be handled realistically to ensure the construction quality. Every link is critical. Zhongda Consulting will explain to you the air pressure welding construction process.

1. Machinery

Oxygen: The purity of the bottled oxygen (O2) used must be above 99.5%, that is, it must reach industrial first-grade purity.

Acetylene gas: It is recommended to use bottled acetylene gas (C2H2) with a purity of less than 98% and a working pressure of 0.05-0.07Mpa. In order to facilitate the stability of the air flow, two bottles of acetylene gas should generally be used in parallel.

Welding clamps: The steel bars should have sufficient clamping capacity, so as not to pinch the steel bars, but also to ensure that the steel bars are not eccentric or bent, and are easy to operate.

Multi-nozzle ring tube heater: that is, a ring-shaped welding torch, which is composed of a gas mixing chamber and a heating ring. Its material and performance, and the number of burners during welding should comply with the relevant requirements of the jet-suction welding pitch. Select according to steel bar diameter and ambient temperature.

Pressor: It consists of a manual oil pump, an oil pressure gauge, a top pressure oil cylinder and an oil pipe. It requires good sealing, resistance to bending, and the ability to increase the axial pressure of the steel bar interface to 35-50Mpa. .

Abrasive cutting machine: used to cut the ends of steel bars flat.

Angle grinder: grinding wheel diameter 100-120mm, used to grind steel bar ends.

2. Working conditions

The equipment must be complete and the quality should be guaranteed. The equipment must be carefully inspected before welding.

Welders must hold a certificate.

Before welding, the gas pressure welding process performance test of the steel bars used was carried out on site. Each batch of steel bars was welded with 6 joints. After visual inspection, three pulls and three bends were performed. Only after the test passed the welding can be officially carried out.

Do a good job in cutting the steel bars. When calculating the cutting length, the compression amount of the welded joints should be considered. The compression amount of each joint is approximately the length of the diameter of one welded steel bar.

3. Operation process

Reinforcement bar end treatment: The ends of the steel bars that undergo air pressure welding must not be horseshoe-shaped, deviated or bent. They should be cut off when necessary to ensure the cross-section of the steel bar ends. It should be at right angles to the axis, without any bending, and be chamfered with an angle grinder to reveal a metallic luster without oxidation. Remove rust, oil, cement, etc. within 100mm of the steel bar end. Grinding the steel bars should be done on the same day to prevent re-rusting after grinding.

Install the extended steel bars: First clamp the clamp on the two processed steel bars. The upper and lower ends of the connected steel bars should be concentric, and the top wire of the fixed clamp should be tightened.

Heating and pressurizing the steel bars: When welding begins, the center of the flame is aligned with the gap between the pressure welding surfaces, causing the surface temperature of the steel bars to reach an incandescent state (about 120 degrees). At the same time, the axial pressure on the steel bars is increased. Press The cross-sectional area of ??the steel bar is 30-40Mpa, so that the expansion diameter of the pressure welding part reaches more than 1.4 times the diameter of the steel bar. The upsetting area is smooth and smooth, with no obvious bulges or collapses.

Remove the clamp: After extinguishing the flame, apply pressure and delay it for a while. After the red color disappears, you can remove the clamp. The weldment is naturally cooled in the air and must not be water-cooled.

4. Quality standards

Guarantee items

The mechanical performance inspection of weldments must be qualified. When conducting mechanical performance tests, the batch size of test specimens should meet the following regulations: in general structures, 200 joints are considered a batch, and those with less than 200 joints are still considered a batch. Sampling method: Cut 3 test pieces from each batch of finished products as tensile strength tests. Their strength shall not be lower than the tensile strength value specified for the grade of steel bars. All three test pieces shall be broken outside the pressure welding surface and shall be in the shape of Plastic fracture. When the test result shows that one test piece does not meet the above requirements, double the number of weldments should be taken for retest. If there is still one test piece that does not meet the requirements, the batch of joints will be deemed unqualified.

Basic items

The expansion shape of the joint should be smooth and there should be no obvious bulges and collapses.

There should be no cracks.

It should not be over-burned, and the surface should not be rough or honeycomb-shaped.

Allowable deviation items

Serial number actual measurement content Allowable deviation inspection method

1 The offset of the two axes of the same diameter steel bar <0.15d feet

< p>2 The offset of the two axes of steel bars with different diameters <4mm visual inspection

3 The maximum diameter of the upsetting area <1.4d feet

4 The length of the upsetting area <1.2d feet< /p>

5 The maximum distance between the top of the upsetting area and the pressure welding surface is <0.25d feet

6. The axis bending of two steel bars is <40 feet

5. Finished product protection And safety measures

Do not disassemble the clamp prematurely to prevent bending and deformation of the joint.

It is not allowed to smash the steel joints after welding, and it is not allowed to pour water on the newly welded joints.

The equipment use and operation safety of gas pressure welding of steel bars should be implemented in accordance with the safety regulations on gas welding in "Welding and Cutting Safety" and the safety technical regulations of "Gas Pressure Welding of Steel Bars". The working pressure of oxygen shall not exceed 0.8Mpa, and the working pressure of acetylene shall not exceed 0.1Mpa, and the gas cylinder shall not be vented, and there must be an appropriate amount of residual gas in the cylinder.

There must be no oil leakage in the hydraulic system, and there must be no flammable or explosive items near the construction site.

Gas pressure welders should wear protective glasses.

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