Exploring the secrets of stainless steel pipes: the multifaceted legend of the backbone of industry

From raw materials to pipes: craftsmanship creates quality

The excellent quality of stainless steel pipes comes from their rigorous and sophisticated production process. Each process carries the persistent pursuit of quality, and each processing is a deep exploration of material performance.

In the raw material preparation stage, selected high-quality stainless steel billets become the cornerstone of pipes. Before these billets are put into production, they must undergo strict composition testing and mechanical property testing to ensure that the content of alloy elements such as chromium, nickel, and molybdenum is accurate and correct, so as to give the pipes excellent corrosion resistance and strength. Composition testing mostly uses advanced spectroscopic analysis instruments, which can quickly and accurately determine the content of various elements to ensure that they meet the corresponding standards and requirements. The mechanical property test evaluates the strength, toughness and other performance indicators of the material through methods such as tensile testing and hardness testing. Only billets that have passed many tests are eligible to enter the subsequent processing links.

The forming process is the core link of stainless steel pipe production, just like a craftsman carefully carving a work of art. Common forming methods include cold rolling, hot rolling and welding, and each process has its unique advantages and applicable scenarios. The cold rolling process rolls the tube blank at room temperature to make the surface of the tube smooth and the dimensional accuracy high. It is suitable for manufacturing high-precision, thin-walled stainless steel tubes, such as those required in medical equipment, precision instruments and other fields. Hot rolling is rolling at high temperature, which can improve the production efficiency and processing performance of the tube. The produced tube has good comprehensive performance and is widely used in industries such as construction and petrochemicals, such as supporting pipes in building structures and oil pipelines. The welding process is to roll the stainless steel sheet into shape and then connect it into a tube by welding. The production process is relatively simple and the cost is low. It is often used to manufacture large-diameter stainless steel tubes and plays an important role in building decoration and urban water supply. ​
After the stainless steel tube is formed, it needs to go through multiple processes such as finishing, quality inspection and surface treatment to become a high-quality product on the market. Finishing treatment includes straightening, cutting, deburring and other operations, which aim to eliminate the deformation and defects of the tube during the processing so that it can meet the specified dimensional accuracy and straightness requirements. The quality inspection link is strictly controlled, using non-destructive testing technologies such as ultrasonic flaw detection and eddy current flaw detection, as well as mechanical performance tests such as stretching, bending, and impact, to ensure that there are no defects such as cracks and pores inside the pipe, and the mechanical properties meet the standards. Only pipes that have passed comprehensive testing can enter the next link. Surface treatment adds a layer of protection and decoration to stainless steel pipes. Common treatment methods include polishing, brushing, and passivation. Polishing makes the surface of the pipe smooth as a mirror, which not only improves the aesthetics, but also reduces the adhesion of dirt on the surface. It is often used in the field of decoration; brushing gives the pipe a unique texture, increases its wear resistance and anti-slip properties, and is widely used in household items, kitchen equipment, etc.; passivation forms a dense oxide film on the surface of the pipe, which effectively improves the corrosion resistance of the pipe and prolongs its service life. It is particularly important in applications in harsh environments such as chemical and marine environments. ​
Material and shape: multiple classifications show style​
The world of stainless steel pipes is rich and diverse. From materials to shapes, every dimension contains unique value and application. Stainless steel pipes of different materials, with their unique chemical composition and crystal structure, show different performance characteristics and are suitable for different industrial scenarios; and the diverse shape design provides the possibility to meet various complex engineering needs. ​
In terms of material, stainless steel pipes are mainly divided into austenitic stainless steel pipes, ferritic stainless steel pipes, martensitic stainless steel pipes and duplex stainless steel pipes. Austenitic stainless steel pipes are the most common type, and their internal crystal structure presents a face-centered cubic lattice, which gives it many excellent properties. It has good corrosion resistance and can remain stable in various chemical environments, thanks to its high chromium and nickel content. These elements form a dense oxide film on the surface of the pipe, which effectively prevents the erosion of corrosive media. In the food processing industry, pipes in contact with various foods need to have good corrosion resistance to prevent the pipes from being corroded and contaminating the food. Austenitic stainless steel pipes can perfectly perform this task. Its plasticity and toughness are also excellent, and it is easy to process and shape. It can be made into pipes of various complex shapes and sizes through various cold processing processes, such as cold drawing and cold rolling. It is widely used in the field of architectural decoration, such as railings and handrails of buildings, which are both beautiful and durable. In addition, austenitic stainless steel pipes also have the characteristics of non-magnetic or weak magnetism, which is of great significance in the manufacture of some electronic equipment that is sensitive to magnetism. ​
The crystal structure of ferritic stainless steel pipes is a body-centered cubic lattice, with a high chromium content as the main feature, and usually contains no nickel or only a small amount of nickel. Its outstanding performance advantage lies in its good oxidation resistance and corrosion resistance, especially in some oxidizing media, it can maintain stable chemical properties. In the automobile exhaust system, ferritic stainless steel pipes can withstand the scouring and oxidation of high-temperature exhaust gas, are not easy to rust and damage, and ensure the normal operation of the exhaust system. It also has the characteristics of high thermal conductivity. In some occasions where rapid heat conduction is required, such as in the manufacture of cookware, it can evenly distribute heat and improve cooking efficiency. However, the toughness of ferritic stainless steel pipes is relatively poor, and brittle fracture is prone to occur in low temperature environments, which to a certain extent limits its scope of application.​
The internal structure of martensitic stainless steel pipe is mainly martensite at room temperature. It is a kind of stainless steel that is both corrosion-resistant and can be strengthened by heat treatment. Its main alloying elements are chromium, iron and carbon. Its hardness and strength can be significantly changed by adjusting the carbon content and carrying out appropriate heat treatment processes. When the carbon content is high, after quenching and tempering, the martensitic stainless steel pipe can obtain extremely high hardness and strength, making it shine in the field of tool manufacturing, such as kitchen knives, industrial cutting tools, etc., which can easily cut various materials and have good wear resistance, extending the service life of the tool. Martensitic stainless steel pipe also has a certain corrosion resistance. It is also widely used in the manufacture of some mechanical parts that do not require particularly high corrosion resistance but have high requirements for strength and hardness, such as shaft parts, gears, etc. ​
Duplex stainless steel pipe combines the advantages of austenitic and ferritic stainless steel. Its microstructure consists of two phases, austenite and ferrite, and the proportion of the two is roughly the same. This unique duplex structure gives it excellent comprehensive performance. In terms of strength, the yield strength of duplex stainless steel pipes is about twice that of austenitic stainless steel, and they can withstand greater pressure and load. In the high-pressure pipeline system in the oil and gas industry, they can safely and stably transport oil and gas resources. Its corrosion resistance is also excellent, especially in the medium containing chloride ions, it has good resistance to pitting, crevice corrosion and stress corrosion cracking, which makes it widely used in the field of marine engineering, such as offshore platform structural parts, submarine pipelines, etc., which can resist seawater corrosion and harsh marine environment. In addition, duplex stainless steel pipes also have good weldability, and the strength and corrosion resistance of welded joints are similar to those of the parent material, which facilitates engineering construction and equipment manufacturing. ​
In addition to the diversity of materials, the shapes of stainless steel pipes are also rich and varied. Common ones are round pipes, square pipes, rectangular pipes and special-shaped pipes. Each shape has its unique structural advantages and applicable scenarios. The round pipe is the most common shape. Its structure is symmetrical. When it is subjected to internal or external pressure, the pressure can be evenly distributed on the pipe wall. Therefore, it has good pressure resistance and is the preferred pipe for fluid transportation. In the fields of urban water supply, oil and gas transportation, etc., round tubes can efficiently and safely transport various fluid media, ensuring a stable supply of energy and water resources. It also has good bending performance and can be processed into various arc-shaped pipes by bending to meet the layout requirements of some special projects. ​
The cross-sectional shape of square tubes and rectangular tubes is square or rectangular. Compared with round tubes, their cross-sectional area is larger, which can provide better support and stability, so they are often used for frame support of building structures. In construction, square tubes and rectangular tubes can form a solid frame structure to bear the weight of the building and various external forces, ensuring the safety and stability of the building. In the field of mechanical manufacturing, they are also widely used in the production of equipment racks, workbenches and other structural parts, providing a solid foundation for mechanical equipment. In addition, the surface of square tubes and rectangular tubes is flat, which is convenient for processing operations such as welding, connection and surface treatment, making them more flexible and convenient in engineering applications. ​
Special-shaped tubes refer to irregularly shaped pipes, such as oval tubes, triangular tubes, D-shaped tubes, etc., which can meet the unique needs of some special projects. In automobile manufacturing, in order to optimize the aerodynamic performance of the car, some exhaust pipes will adopt a special-shaped pipe design so that they can better adapt to the spatial layout of the car engine compartment, while reducing exhaust resistance and improving engine performance. In the aerospace field, special-shaped pipes are also commonly used to manufacture aircraft wing structures, engine components, etc. These components need to have special shapes and performance to meet the use requirements of aerospace vehicles under complex working conditions. The manufacturing difficulty of special-shaped pipes is relatively large, and special molding processes and molds are required, but its appearance provides an effective solution to some complex engineering problems.