In general, the process of manufacturing stainless steel pipe fittings in accordance with the order including cutting, forming, heat treatment, surface treatment, cutting, nondestructive testing, surface protection and the logo, the following step by step under the details.
The first is the cutting, the production of stainless steel pipe fittings used in the material is usually pipe, stainless steel plate and stainless steel bar, according to the characteristics of the material and the shape of the product to choose blanks blanking method. Blank shape, size and other requirements are also based on different product specifications. For stainless steel pipe, the commonly used methods of cutting the band sawing machine or bow saw cutting, gas cutting, plasma cutting. For stainless steel sheet, often used cutting method is gas cutting, plasma cutting, punching punch. For stainless steel bars, frequently used blanking methods include band sawing or bow sawing, blanking and cutting.
The second step is forming, also known as welding, all stainless steel pipe production and forming processes are inseparable from this process. This article describes the heating and welding in the next part of the forming process.
The heating refers to the requirement of deformation of the stainless steel material in the forming process and heating of the billet during forming. The heating temperature is generally determined by the material and the process needs. Hot elbow or hot elbow forming, the general use of IF or high frequency induction heating method, but also the use of flame heating method. This type of heating process is a continuous heating of the elbow or elbow forming process, the tube is heated during the movement and complete the forming process. Hot elbow, hot tee or forging forming, the general use of reflective furnace heating, flame heating, induction heating or electric furnace heating and other methods. Such heating process is to first heat the stainless steel tube to the required temperature, and then into the mold or forging forming.
The welding, there are two cases, one is the use of pipe production of pipe, the use of pipe forming process and the use of seamless pipe forming process is basically the same, the pipe forming process does not include the welding process, the other is from the pipe factory To complete the pipe forming the welding process required, and then welded into the tube after the stainless steel plate tube and then pressed the tee and so on.
The third step is heat treatment, this process is an important part of stainless steel pipe production. After heating, heat preservation and cooling heat treatment step, to remove forming hardening, residual stress, deformation of metal defects and so on, so that after the formation of stainless steel pipe fittings of the metal structure, performance changes, return to the pre-deformation state or to make its performance Be improved and improved.
Often used heat treatment equipment is the reflection furnace, electric furnace, etc., the control method is the thermocouple inside the furnace through the sensor connected to the temperature – time automatic recorder control device.
Different pipe products in the standard heat treatment requirements are not the same. Not all of the deformed pipe must be heat treated, in general, for the low-carbon steel pipe fittings the final forming temperature of not less than 723 ℃, no longer need to heat treatment, due to the temperature under the conditions of its final organization Usually normalized, below this temperature or higher than 980 ℃ to be heat treatment, alloy steel or stainless steel tube regardless of the use of cold forming or thermoforming, should be heat treatment. Routine inspection The effect of heat treatment is usually to see the hardness test situation.
The fourth step is the surface treatment, the method is basically sandblasting, shot blasting, grinding, pickling, etc., so as to remove the surface rust, scratches, etc., to improve the surface smoothness, to follow-up processing, testing needs. After the shot blasting stainless steel pipe fittings, the surface hardness will be slightly increased.
The fifth step is cutting, it is to complete the welding of stainless steel pipe ends, the size of the structure, shape and position tolerance process. For some pipe products, cutting and processing, including internal and external diameter of the processing. Cutting is usually done by a dedicated machine or general-purpose machine tool. For oversized pipe fittings, when existing machine tools can not meet the machining requirements, they can be finished by other processes, such as gas cutting and sanding after large-diameter elbows . Stainless steel pipe usually appearance, size inspection after cutting.
The sixth step is non-destructive testing, non-destructive testing is to detect stainless steel materials and pipe processing process may produce defects in an important process. Most stainless steel pipe product standards for non-destructive testing requirements have some provisions, but the requirements are not the same. In addition to the non-destructive testing of stainless steel standards and ordering requirements, some of the more stringent quality control manufacturers also make non-destructive testing requirements based on materials, processing techniques, and internal quality controls to ensure the quality of the final product.
The actual work of non-destructive testing of stainless steel pipe to determine the level of acceptance should be based on the order requirements or standards of the specific provisions. As the stainless steel pipe is usually the original surface of the original pipe, plate or forgings, stainless steel pipe surface quality of the non-destructive testing, if there is no clear grade requirements can be Ⅱ grade, for mezzanine and crack such defects are not easy to determine the depth of As unqualified. For non-destructive testing of internal quality of pipe fittings, if there is no clear grade requirement, ray inspection should be carried out in grade Ⅱ and ultrasonic inspection should be grade Ⅰ.
In order to avoid the stainless steel tube during heat treatment may have a defect situation, the final non-destructive testing of stainless steel pipe fittings to be carried out after the heat treatment.
The seventh step is the surface protection, the use of pickling stainless steel pipe passivation approach. The main purpose of stainless steel pipe surface protection is anti-corrosion, but also to achieve beautiful appearance of the product results. In general, the order surface protection put forward specific requirements, the manufacturer according to the requirements of the order to complete the stainless steel pipe surface protection.
The last is marked on the stainless steel tube, the mark is an integral part of the product is to achieve the basis of traceability requirements. In general, the standard stainless steel pipe on the logo content and methods to do some provisions. Stainless steel pipe signs usually include the manufacturer’s trademark, name, material grade, specifications and other requirements of the order. Signs are mainly permanent signs, such as stamping, sculpture, galvanic corrosion, there are also non-permanent signs, such as jet printing, labels and so on.
In addition, in addition to some of the above conventional production processes, in order to control the quality of raw materials, the production plant to complete the inspection of raw and auxiliary materials to ensure the accuracy of the use of materials to meet some special requirements, but also for example, microstructure , Intergranular corrosion, ferrite and other tests and tests to ensure that the final product quality in line with the needs of use.
Source: China Pipe Fittings Manufacturer – Yaang pipe fitting Industry Co., Limited (www.yaang.com)