Stainless steel is one of the most popular and versatile materials. Stainless steel is a ferroalloy with a minimum chromium content of 10.5%. Alloying elements such as nickel, molybdenum, titanium, carbon, nitrogen, and copper can improve the strength, formability, and other properties of stainless steel. Different alloys provide different levels of corrosion resistance. Compared with carbon steel, stainless steel alloy has higher low-temperature toughness, higher working hardening rate, higher strength and hardness, greater ductility, and more attractive appearance.
Seamless stainless steel pipe single from the literal meaning can be seen is the steel around no welding seam. Seamless stainless steel tubes are used for applications requiring high-temperature strength and excellent corrosion resistance. In addition, stainless steel is easy to clean and does not tarnish. Seamless stainless steel pipes are usually thought of as circular, but stainless steel tubes can be made in a variety of shapes and thicknesses from ellipses, circles, and rectangles to flat shapes. The American Institute of testing and materials has established standards for stainless steel tubes to benefit manufacturers and buyers. Stainless steel pipes are available in different grades and finishes to suit their intended industry and applications.
The overall process of manufacturing seamless stainless steel tubes
1. Welding and seamless production in pipe making process.
Seamless tubes and pipes, from car manufacturing to gas pipes, can be welded with alloys (metals made of different chemical elements) or constructed seamlessly from furnaces. Although welded tubes are pressed together by means of heating and cooling and are used for heavier, more rigid applications (such as piping and gas delivery), seamless tubes are made by stretching and hollowing out for lighter, thinner purposes (such as cycling and liquid delivery). This method of production contributes greatly to the design of steel tubes. Changes in diameter and thickness can cause differences in the strength and flexibility of large projects (such as gas delivery lines) and precision instruments (such as hypodermic needles). The closed structure of the tube, whether round, square or any other shape, can be used for any purpose from liquid flow to corrosion prevention.
2. Step by step engineering of welded and seamless stainless seamless tubes and pipes.
The entire process of seamless tubes and pipes manufacturing involves converting coarse steel into an ingot, billet, slab, and billet (all of which are weldable materials), creating a pipeline on the production line and then shaping it into the desired product.
3. The steel manufacturing process for welded and seamless stainless seamless tubes.
To create ingot, billet, slab, and billet, iron ore and coke (a carbon-rich substance from heated coal) are melted into a liquid substance in a furnace, then sanded with oxygen to produce molten steel. The material is cooled into ingots, large steel castings used to store and transport materials, which are formed between rollers at high pressure. Some ingots are stretched by steel rollers into thinner, longer blocks, thus producing a generous billet, the intermediate between steel and iron. They are also rolled through stacked rollers into rectangular billets with rectangular cross-sections.
4. More rolling equipment is flattened – a process known as die-casting – blank forming.
These are pieces of metal with circular or square cross-sections that are longer or thinner. Flying shears cut billets into precise positions in order to stack billets and form seamless tubes. The plates are heated to about 2,200 degrees Fahrenheit (1,204 degrees Celsius) until they are malleable, then thinned into thick strips of carbon about a quarter of a mile (0.4 kilometers) long. The steel is then cleaned using sulfuric acid tanks, cold and hot water, and sent to the pipe plant.
5. Develop welded and seamless stainless steel tubes.
For welded tubes, the uncoiler loosens the uncoiler and passes it through the roller to crimp the edges and form the tube. The welding electrodes seal the ends together using an electric current before the high-pressure roll tightens them. The process can produce pipes at up to 1,100 feet (335.3 m) per minute. For stainless seamless tubes and pipes, the process of heating and high pressure rolling the billet causes the billet to have a hole in the center. The mill punctures the tube to obtain the desired thickness and shape.
6. Further processing and galvanizing.
Further treatment may include straightening, tightening (cutting out a narrow groove at the end of the pipe), or coating with zinc protective oil or galvanizing to prevent rust (or necessary for the purpose of the pipe). Galvanization usually involves an electrochemical and electrodeposition process of zinc coating to protect the metal from corrosive materials such as saltwater. The method prevents harmful oxidants in water and air. Zinc ACTS as the anode for oxygen, forming zinc oxide, which reacts with water to form zinc hydroxide. These zinc hydroxide molecules form zinc carbonate when exposed to carbon dioxide. Finally, a thin, impermeable layer of insoluble zinc carbonate attaches to the zinc to protect the metal. A thinner form of electroplating is commonly used in automotive parts that require antirust paint so that hot-dip plating will reduce the strength of the base metal. Stainless steel is produced when stainless steel parts are galvanized as carbon steel.
The differences between hot and cold rolled seamless tubes and pipes
1. The local buckling of profiles is allowed in cold-rolled steel so that the bearing capacity of steel bars after buckling can be fully utilized. However, hot rolled steel does not allow the section local buckling.
2. The distribution of residual stress on the cross-section of hot – rolled and cold – rolled steel is different. The distribution of residual stress on the section of cold-formed thin-walled steel is curved, while that on the section of hot-rolled or welded steel is thin-film.
3. The free torsion stiffness of hot rolled steel is higher than that of cold-rolled steel, so the torsion property of hot rolled steel is better than that of cold-rolled steel. Cold-rolled seamless tubes and pipes are divided into ordinary steel tubes, medium and low-pressure boiler tubes, high-pressure boiler tubes, alloy seamless tubes and pipes, stainless steel tubes, petroleum cracking tubes, other seamless tubes, and pipes, also including carbon thin-walled steel tubes, alloy thin-walled stainless steel tubes, stainless steel tubes, shaped seamless tubes and pipes.
4. The outer diameter of the hot-rolled seamless stainless tube is generally greater than 32mm and the wall thickness is 2.5-75mm. The diameter of the cold-rolled seamless tube can reach 6mm and the wall thickness can reach 0.25mm. The thin-walled outer diameter of the tube can reach 5mm and the wall thickness is less than 0.25mm. Cold rolling is more accurate than hot rolling.
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