The uniform deformation of hot-dip galvanized square tube is a simple case of object deformation. Its characteristics are: the plane and the line remain plane and straight line after deformation. The parallel lines and parallel planes remain parallel after deformation. The cube perpendicular to the strain principal axis has only linear size changes after uniform deformation without shear deformation. If the deformed body is a sphere, it becomes an ellipsoid after deformation.
It can be seen that the characteristic of uniform deformation is that the displacement of each point of the object is a linear function of the original coordinates, and the uniform deformation has only three principal strains and no shear strain.
In the theory of metal pressure processing, especially in the theory of rolling tube, logarithmic strain is widely used to represent uniform deformation. Logarithmic strain can more accurately represent the degree of deformation of an object than the relative deformation coefficient.
Hot-dip galvanized square tube is also called welded tube, which is a steel tube made of steel plate or steel strip after curling and welding. The production process of welded steel pipe is simple, the production efficiency is high, the variety and specifications are many, and the equipment investment is small, but the general strength is lower than that of seamless steel pipe. Since the 1930s, with the rapid development of high-quality hot-dip galvanized square tube rolling production and the advancement of welding and inspection technology, the quality of welds has been continuously improved, the varieties and specifications of welded steel pipes have increased, and they have replaced seamless steel pipes in more and more fields. Welded steel pipes are divided into straight seam welded pipes and spiral welded pipes according to the form of welds. The production process of straight seam welded pipes is simple, the production efficiency is high, the cost is low, and the development is relatively fast. The strength of spiral welded pipes is generally higher than that of straight seam welded pipes. Narrower billets can be used to produce welded pipes with larger diameters, and billets of the same width can also be used to produce welded pipes with different diameters. However, compared with straight seam pipes of the same length, the weld length increases by 30~100%, and the production speed is lower. Therefore, smaller diameter welded pipes mostly use straight seam welding, while large diameter welded pipes mostly use spiral welding.
Hot-dip galvanized square pipes for low-pressure fluid transportation are also called general welded pipes, commonly known as black pipes. They are welded steel pipes used for conveying generally low-pressure fluids such as water, gas, air, oil and heating steam and other purposes. The wall thickness of the steel pipe joint is divided into ordinary steel pipe and thickened steel pipe; the connection end form is divided into non-threaded steel pipe and threaded steel pipe. The specifications of the steel pipe are expressed in nominal diameter, which is an approximate value of the inner diameter. It is usually expressed in inches, such as 11/2. In addition to being used directly to transport fluids, welded steel pipes for low-pressure fluid transportation are also widely used as the original pipes of galvanized welded steel pipes for low-pressure fluid transportation.
