Stainless steel pipe is a hollow long round steel material, which is widely used in industrial transportation pipelines and mechanical structural parts such as petroleum, chemical industry, medical treatment, food, light industry, mechanical instrumentation, etc. In addition, when the bending and torsional strength are the same, the weight is light, so it is also widely used in the manufacture of mechanical parts and engineering structures. It is also often used as furniture and kitchenware.
Stainless steel pipes generally use three hardness indexes of Brinell, Rockwell, and Vickers to measure their hardness.
1. Brinell hardness
Among the stainless steel pipe standards, Brinell hardness is the most widely used, and the hardness of the material is often expressed by the indentation diameter, which is intuitive and convenient. However, it is not suitable for steel pipes with harder or thinner steel.
2. Rockwell hardness
The Rockwell hardness test of stainless steel pipe is the same as the Brinell hardness test and is the indentation test method. The difference is that it measures the depth of the indentation. The Rockwell hardness test is a widely used method at present, in which HRC is second only to Brinell hardness HB in the steel pipe standard. Rockwell hardness can be applied to the determination of metal materials from extremely soft to extremely hard. It makes up for the Brinell method. It is simpler than the Brinell method, and the hardness value can be read directly from the dial of the hardness machine. However, because of its small indentation, the hardness value is not as accurate as of the Brinell method.
3. Vickers hardness
The Vickers hardness test of stainless steel pipe is also an indentation test method, which can be used to determine the hardness of very thin metal materials and surface layers. It has the main advantages of the Brinell and Rockwell methods, and overcomes their basic shortcomings, but it is not as simple as the Rockwell method, and the Vickers method is rarely used in steel pipe standards.
Stainless steel pipes are divided into ordinary carbon steel pipes, high-quality carbon structural steel pipes, alloy structural pipes, alloy steel pipes, bearing steel pipes, stainless steel pipes, and bimetallic composite pipes, coating and coating pipes to save precious metals and meet special requirements. There are many types of stainless steel pipes, different uses, different technical requirements, and different production methods. The currently produced steel pipe has an outer diameter ranging from 0.1 to 4500 mm and a wall thickness ranging from 0.01 to 250 mm. In order to distinguish its characteristics, steel pipes are usually classified as follows.
Stainless steel pipes are divided into two categories: seamless pipes and welded pipes according to production methods. Seamless steel pipes can be divided into hot-rolled pipes, cold-rolled pipes, cold-drawn pipes and extruded pipes. Cold-drawn and cold-rolled pipes are secondary to steel pipes Processing; welded pipe is divided into straight seam welded pipe and spiral welded pipe.
Stainless steel pipes can be divided into round pipes and shaped pipes according to the cross-sectional shape. Special-shaped tubes include rectangular tubes, rhombic tubes, elliptical tubes, hexagonal tubes, octagonal tubes, and asymmetric cross-section tubes. Special-shaped tubes are widely used in various structural parts, tools and mechanical parts. Compared with round tubes, special-shaped tubes generally have larger moments of inertia and section modulus, and have greater bending and torsion resistance, which can greatly reduce the weight of the structure and save steel materials.
According to the shape of longitudinal section, stainless steel pipe can be divided into equal section pipe and variable section pipe. Variable section tubes include conical tubes, stepped tubes and periodic section tubes.
Stainless steel pipe can be divided into smooth pipe and wire pipe (with threaded steel pipe) according to the state of the pipe end. The wire tube can be divided into ordinary wire tube (pipe for conveying water, gas and other low pressure, using ordinary cylindrical or conical pipe thread connection) and special threaded pipe (petroleum, geological drilling pipe, for important wire pipe, use Special thread connection), for some special pipes, in order to make up for the influence of the thread on the strength of the pipe end, the pipe end is usually thickened (internal thickening, external thickening or internal and external thickening) before the wire.
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