Production of seamless cold-worked pipes for general use, thin-walled pipes from carbon and alloy steels
To begin with, we will find out why, by and large, seamless pipes are needed (see also the article “Transparent pipe: characteristics and materials”).
Alas, it is difficult for them to come up with the use of plumbing fixtures or any other home equipment when they do-it-yourself installation. The price of the products is too high, and the durability is obviously excessive for any reasonable purpose.
In short, they are in demand where extreme strength is needed (first of all, to break). Another development, much more inexpensive and technologically advanced – the production of welded pipes – has a significant drawback.
Production development
Billets for production – the so-called conversion pipes, which are produced by the method of warm deformation from cylindrical blanks – rods. The rod is kept in a furnace to a temperature at which the steel becomes plastic and is transformed into a hollow cylinder – a sleeve – on the so-called piercing mill.
To put it simply, its forthcoming processing is reduced to rolling on a group of successive rollers with a slowly decreasing size on a stationary or rotating mandrel. The key difference from hot-rolled pipes is that, unlike them, cold-worked pipes undergo main operations at temperatures below the recrystallization mark.
What do the main production steps look like?
Cutting blanks into pieces of measured length.
Chemical treatment required to remove rust from the scale and surface. For carbon steels, solutions of acids (sulfuric and hydrochloric) are used, for alloyed ones, caustic soda melt with an oxidizing agent NaNO3. At the end of etching, the workpieces are sequentially washed with warm water in a bath, then with a jet of cold water under pressure, after which 20-30 minutes. dried at a temperature of 150 – 180C.
The workpieces are sent to baths with technological coatings and lubrication, which reduce friction losses during the upcoming processing.
After that, the conversion pipes go to the cold rolling mill (cold rolling of pipes), where, during rolling, the thickness of their walls is significantly reduced. Sizing rolls in one moment of steam increase the length of the workpiece.
Upcoming machining includes straightening, face trimming, sizing in reduction rolls or drawing in a ring calibrator. The pipe is completely formed, transforming into a product with a given diameter and ideal geometry.
The last stage before going through quality control is heat treatment. During tempering (heating to a temperature 50 degrees above the recrystallization point), followed by gradual cooling, the accumulated internal stresses of the material are removed, its viscosity and plasticity increase.
PRODUCTION OF THIN WALLED PIPES
Rolled metal allows the production of various parts and products, among which thin-walled pipes are quite popular. The scope of their application in construction cannot be underestimated, since they are universal in operation. Mechanical engineering, architectural structures, parts of various equipment – this is only a small part of where they can be applied. The production of thin-walled pipes in Ukraine is a part of the processing industry, which is rapidly developing and without which it is difficult to imagine the structures we are used to.
FEATURES OF THIN WALLED PIPE PRODUCTION
There are several types of thin-walled pipes according to production technology, including:
The characteristics of a steel pipe are: ductility, dimensional accuracy, strength, weldability. Their use is suitable for lightweight structures, in which a large load is not provided. Subdivided into welded and seamless. Accordingly, the first type is suitable for structures where plasticity is required. Seamless are applicable in situations where strength is a priority. Steel pipes can be manufactured using hot or cold deformation methods.
Electrowelded.
Pipes, the seams of which are connected by electric welding, are produced in a rather convenient way and are reliable in operation. The brazing of the pipe edges guarantees resistance to stress and environmental influences. The raw material for electrowelded steel is most often alloyed or carbon steel in sheets. Also, as in seamless, cold-deformed and hot-deformed pipes are distinguished. Cold-deformed is applicable in the furniture industry, which is facilitated by its flexibility and quality, but the cost exceeds that of hot-deformed pipes.
Order seamless cold-worked pipes. Order thin-walled pipes