What is a small diameter seamless steel pipe?
Generally speaking, the seamless steel pipes used in daily life are of normal caliber, and small-diameter seamless steel pipes are only used in some special places. Today, I will introduce you to the relevant knowledge of small-diameter seamless steel pipes, which will help you to use this kind of pipe better in the future. Generally speaking, seamless steel pipes with small outer diameters are collectively referred to as small-diameter seamless steel pipes, but there is still a specific range. Generally, steel pipes with diameters below 89mm and above 4mm can be called small-diameter seamless steel pipes.
In most cases, small-diameter seamless steel pipes are also used as pipes for conveying fluids. Compared with solid steel such as round steel, they are lighter in weight when the bending and torsional strength is the same. They are an economical cross-section steel and are widely used in the manufacture of structural parts and mechanical parts, such as oil
drill pipes, automobile transmission shafts, bicycle frames, and steel scaffolding used in construction.
The general specifications of small-diameter seamless steel pipes are between 6-89mm in outer diameter, and their diameters are relatively small. Wall thicknesses of 1-12mm can also be divided into small-diameter thick-walled seamless pipes and small-diameter thin-walled seamless pipes. The weight calculation formula is: [(outer diameter-wall thickness)*wall thickness]*0.02466 = kg/meter (weight per meter)
Problems to pay attention to when producing small-diameter seamless steel pipes
Cold drawing is a material processing technology. For metal materials, cold drawing refers to drawing the material at room temperature in order to achieve a certain shape and certain mechanical properties. Compared with hot forming, cold-drawn products have the advantages of high dimensional accuracy and good surface finish. Here are the issues that should be paid attention to when producing cold-drawn small-diameter seamless steel pipes
1. First, the rough pipe
The wall thickness of the rough pipe should be uniform, with few defects on the inner and outer surfaces; equipment for polishing the outer surface and cleaning the inner hole defects should be configured.
2. The second is re-inspection
Compared with ordinary
cold-drawn steel pipes, the production of cold-drawn small-diameter seamless steel pipes adds a hot-rolled rough pipe pickling re-inspection process, mainly to ensure that there are no defects such as folds and cracks on the outer surface of the rough pipe, and to exclude the rough pipes with defects such as folds, severe scratches, and pitting on the inner surface.
3. The second is tools
The surface finish of the tools used in the production of cold-drawn small-diameter seamless steel pipes is generally required to be above Ra0.4, the dimensional accuracy is above H3, and the hardness is required to be above HRC70. At the same time, it is required that the head or the mold should not stick to the steel during the drawing process.
4. The second is annealing
Annealing is a very important process in all cold-drawn tube production. The quality of annealing affects both the performance of the steel pipe and the removal of the oxide scale. Cold-drawn precision steel pipes need to be equipped with non-oxidizing bright annealing furnace equipment.
5. Finally, pickling
During the sulfuric acid pickling process, cold-drawn small-diameter seamless steel pipes are prone to form "black slag" mainly composed of Fe2O3 and Fe3O4, which will form surface black spots in subsequent production. Fe2O3 and Fe3O4 are easily soluble in hydrochloric acid. To prevent the formation of black spots, 5-10g/l of Na is added to the acid pool.
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