Hydraulic Hard Pipe Process Plan and Process Control

1. Tube Bending

The automatic servo tube bending machine, when used with specialized custom molds, can quickly achieve multi-angle hard tube bending in a single operation. Bending accuracy is controlled within ±0.1. The processing accuracy and consistency of each product can be achieved through computer control, reducing manual operation and errors, lowering production costs and scrap rates, and meeting the high-precision requirements of the engineering machinery industry. Tubes with an outer diameter less than 60 mm can be processed using cold bending. For tubes with an outer diameter of 100 mm or more, either cold or hot bending can be used. For tubes with an outer diameter greater than 300 mm, hot bending is generally employed. During the process, the flatness of the bent tube is closely monitored.

2. Welding

Welding equipment uses fully automatic argon arc welding machines;

The welding process complies with domestic Doosan standards: no beveling, no welding wire added, and direct welding of steel pipes with wall thicknesses between 3mm and 7mm;

Selection of welding processes: acetylene gas welding is primarily used for carbon steel pipes with wall thicknesses of 2mm or less. Arc welding is primarily used for carbon steel pipes with wall thicknesses greater than 2mm. Welding of pipes is best performed using argon arc welding. For pipes with wall thicknesses greater than 5mm, TIG welding should be used for the base layer, and arc welding for the filler layer. In necessary cases, welding should be performed using the method of filling the pipe interior with protective gas.

Spot welding with three or more points, with weld spot sizes of 3-4mm, and no porosity or cracking;

During welding, the distance between the weld seam and the tungsten electrode should be 2-3cm.

After welding, 100% pressure testing is conducted to inspect the weld seam quality.

3. Phosphating

After welding, the pipes undergo high-temperature acid washing and phosphating, which provides excellent rust prevention and long-lasting corrosion resistance. This is highly beneficial for maintaining the cleanliness of hydraulic fluid, effectively extending the service life of hydraulic components, and reducing maintenance costs for the hydraulic system.

Control the concentration of the phosphating solution.

Clean the water tank with circulating water and replace it regularly.

When packaging the products, ensure that no cavities form in the middle of the pipes.

4. Coating

After acid washing and phosphating, the hydraulic pipes have a longer rust-resistant surface. The spraying process provides a refined protective layer with good adhesion. After spraying, the product surface has high hardness, good smoothness, and prolonged protection.

Cover the pipe ends; when hanging hooks, re-inspect the coverage area; no paint should adhere;

After coating, the surface should have no wrinkles, defects, or peeling.