Innovative Manufacturing Process of Seamless Steel Tube for High Pressure Boiler

Seamless boiler tube have been widely used in hydraulic systems and diesel fuel systems. At present, cold-rolled or cold-drawn capillary tubes are generally used to manufacture high-precision, small-diameter, high-pressure seamless steel pipes. Although they can also meet the technical requirements, there are still the following problems: Although the cold-drawn process has high production efficiency, it will inevitably lead to The internal defects of the material are expanded and the structure is loose. Compared with the cold rolling process, the pressure resistance and the quality of the inner and outer surface of the steel pipe manufactured by it are relatively low; while the cold rolling process can increase the density of the material, and the surface quality is good. The dimensional accuracy is high, but there is a problem of low production efficiency, especially for small diameter steel pipes, which must be cold rolled 2 to 3 passes in order to meet the required technical requirements, and it is difficult to meet the needs of efficient production. To this end, the author proposes a process with high production efficiency, good quality, high dimensional accuracy, and suitable for the manufacture of small diameter high pressure seamless steel pipes, and has achieved good application effects.

Manufacturing process

The manufacturing process of high-precision, small-diameter, high-pressure boiler seamless steel pipes, which are mainly used for pretreatment, cold rolling, oxygen-free bright annealing, re-pretreatment, shrinking, and continuous cold drawing for capillary tubes with a diameter of ~15 mm~O30 mm, Oxygen-free bright heat treatment, straightening and truncation, non-destructive testing and surface treatment and other technical measures.

High-precision, small-diameter, high-pressure boiler seamless steel pipe production process

The specific operation steps of high-precision, small-diameter, high-pressure boiler seamless steel pipe are as follows:

(1) Pickling, phosphating and saponification treatments for capillaries with a diameter of 15 mm to 30 mm.

(2) One pass of cold rolling is performed on the pretreated steel pipe.

(3) Perform oxygen-free bright annealing on the steel pipe after one pass of cold rolling.

(4) Pickling, phosphating, and saponification treatments are performed on the steel pipes that have undergone anaerobic bright annealing treatment.

(5) The steel pipes that have undergone oxygen-free bright annealing and pretreatment are subjected to head shrinking before cold drawing.

(6) Carry out 1 to 3 passes of continuous cold drawing of the steel pipe after shrinking. The number of cold drawing passes is determined according to the allowable diameter reduction of the material, and the diameter of the pipe is used to determine whether to use the cold drawing short core die .

(7) Perform oxygen-free bright normalizing or stress relief annealing on the seamless steel pipe after cold drawing.

(8) Straightening and truncating the steel pipe after heat treatment.

(9) Non-destructive testing of steel pipes after straightening and truncation.

(10) Perform galvanizing, military green passivation or blackening treatment on the steel pipes that are confirmed to be free from flaw detection.

Advantages of high-precision small-diameter high-pressure boiler tube:

Combining the cold rolling process and the cold drawing process organically, it not only gives full play to the advantages of the cold rolling process to increase the material density, good surface quality, and high dimensional accuracy, but also maintains the advantages of high production efficiency of the cold drawing process; especially It has significant economic and social benefits for the manufacture of high-precision, small-diameter, high-pressure boiler seamless steel pipes.