The specific production method of L245 line pipe

A production method of L245 line pipe

This patent relates to a production method of line pipe, especially a production method of L245 line pipe.

For the production of large-diameter, thick-walled, and extra-thick-walled seamless L245 line pipes, the traditional methods are the pipe jacking-extrusion method and the Pilger method. The obvious shortcomings of the above two production methods are: 1. Low tube blank formation rate; 2. Low productivity; 3. Poor quality of the inner and outer surfaces of the product, and inaccurate geometric dimensions.

At the end of the 1960s, the Italians completed the MPM tube rolling process (that is, the two-roll continuous tube rolling process) and obtained a patent. This is the first process patent after the first continuous tube rolling mill was put into production in 1890 in the United States. Subsequently, by the beginning of this century, more than 20 sets of continuous tube rolling mills worldwide were in production. Among them, China accounted for more than half, reaching 12 sets. In the past few years, most of China’s continuous tube rolling mills were mainly MPM. In recent years, the German PQF unit (three-roll continuous rolling process), known as the world’s most advanced technology, has achieved success in Tianjin L245 Line Pipe Group. However, the specifications of the above-mentioned units have a maximum diameter of 480mm and a wall thickness of 60mm, which means that the domestic Pilger unit (including the unit under construction) and the Wuhan 471 unit are included in the production of large-diameter, thick-walled, and special-purpose units. For thick-walled units, the outer diameter and wall thickness of the L245 line pipe can only be 580mm and 80mm, and the rotary expansion unit can only produce the maximum 1422mm L245 line pipe.

The present invention is a process flow established based on a 630mm large-scale hot continuous rolling seamless L245 line pipe unit, and its process plan is:

The tube billet is heated to 1000-1200°C through a ring heating furnace, and then discharged from the furnace through a two-way thermal centering unit for two-way thermal centering, and then enters the cone-roller puncher. The front of the puncher is equipped with a rotating pinch device, and the back of the puncher The rod actively rotates to ensure that the wall thickness of the front and rear ends of the capillary is uniform and improve the success rate. The capillary after the hole is drilled enters the five-stand three-roller limited mandrel rolling mill with an air reducer for rolling. Then, it enters the three-frame stripping unit, after stripping, the head and tail are cut by a hot saw, and then into the fast chain bed. When large-size seamless pipes need to be produced, the capillary tube enters the reheating furnace through a fast chain bed, heated to 1000-1100℃, and then undergoes tension reduction through 12-14 micro-tension reducers; if small-size L245 is produced In the case of line pipe, the reduced L245 line pipe continues to enter the induction reheating furnace for heating to 1000-1100°C, and then passes through 28-32 tension reducers to obtain small-size L245 line pipe. The finished L245 line pipe is cut to length by a pipe saw, and then enters the walking cooling bed. The cooled L245 line pipe enters the multi-roll straightener for straightening. The multi-roll straightener can be used to make the L245 pipeline The tube receives more force, the straightening process is stable and the effect is better. The straightened L245 line pipe has been tested and qualified and packed and put into storage. The light pipe produced by the 630mm unit can produce 711mm-1422mm line pipes after one or two rotations, especially all line pipes below 1422 can be produced.