How is seamless pipe formed?

Mandrel Mill Process

In the Mandrel Mill Process, a solid round (billet) is used. It is heated in a rotary hearth heating furnace and then pierced by a piercer. The pierced billet or hollow shell is rolled by a mandrel mill to reduce the outside diameter and wall thickness which forms a multiple length mother tube. The mother tube is reheated and further reduced to specified dimensions by the stretch reducer. The tube is then cooled, cut, straightened and subjected to finishing and inspection processes befor shipment.

This process is used to produce smaller sizes of seamless pipe, typically 1 to 6 inches (25 to 150 mm) in diameter. The steel billet is heated to 2,370°F (1,300°C) and pierced. A mandrel is inserted into the tube and the assembly is passed through a rolling (mandrel) mill. Unlike the plug mill, the mandrel mill continuously reduces the wall thickness with a series of pairs of curved rolls set at 90° to each other. After reheating, the tube passes through a multi-stand stretch-reducing mill to reduce the diameter to the finished diameter. The tube is then cut to length before heat treatment, final straightening, inspection and hydrostatic testing.

Seamless pipes are formed using a process known as extrusion. Here is a general overview of how seamless pipes are formed:

The extrusion process allows for the production of seamless pipes with no seams or joints, resulting in a pipe that is stronger, more reliable, and better suited for high-pressure and high-temperature applications.

It's important to note that the specific details of the manufacturing process may vary depending on factors such as the type of seamless pipe, the material used, and the desired specifications.

The method of extending the service life of seamless pipe

Seamless steel pipes have hollow sections and are widely used as pipes for conveying fluids, such as pipes for conveying oil, natural gas, gas, water and certain solid materials. The seamless pipe has a certain corrosion resistance, but in order to prolong the service life of the seamless pipe in some extreme environments, it is necessary to remove the oxide layer on the surface of the product. The main cleaning method is pickling. After cleaning, electrolytic cleaning is required again.

1. The seamless steel pipe must wear labor protection supplies before pickling. The on-site working environment should also be checked in detail, mainly to check whether the hoisting of the steel pipe is intact, and work can only be carried out after confirming that it is intact.
2. When pickling seamless steel pipes, the pickling method is mainly hydrochloric acid pickling. Usually, the content of hydrochloric acid is preferably 18% to 20%.
3. The staff also need to know the concentration and temperature of the acid solution in this tank and the tonnage of the pickling pipe before operation.
4. The weight of pickling steel pipe is controlled between 2-5 tons each time, and the time is controlled within 5-15 minutes. Time needs to be adjusted according to body weight. During the pickling process of steel pipes, frequent vibrations are also required. When lowering the pipe into the acid tank, the steel pipe should be tilted to prevent accidental injury by hydrochloric acid.

The seamless pipes stored in the warehouse waiting to be put into use need to do the following work

The warehouse shall not be piled together with acid, alkali, salt, cement and other materials that are corrosive to steel. Steel materials of different types should be stacked separately to prevent mixing and contact corrosion.

1. Large steel sections, rails, steel plates, large-diameter steel pipes, forgings, etc. can be stacked as needed.
   
2. Some small steel products, thin steel plates, steel strips, silicon steel sheets, small-diameter or thin-walled steel pipes, various cold-rolled and cold-drawn steel products, high-priced and easily-corroded metal products can be stored in the warehouse.
   
3. The warehouse should be selected according to the geographical conditions. Ordinary closed warehouses are generally used, that is, warehouses with ceilings, walls, tight doors and windows, and ventilation devices.