The main technological process of steel pipe fittings manufacture
Blanking forming (welding) surface heat treatment processing cutting nondestructive testing of surface protection
Pipe materials used mainly for pipes, sheet and rod, according to the material properties and the shape of the billet blanking methods used for the product. Blank shape, size and other requirements according to the technological requirements of the different products.
For the pipe, the cutting method with common sawing machine or bow sawing machine cutting, gas cutting, plasma cutting.
For plate, blanking methods with gas cutting, plasma cutting, punching, punching.
For the bar, the cutting method with common sawing machine or bow sawing machine cutting, punching and shearing cutting.
(2) forming (welding)
For all the pipe manufacturing process, forming is the indispensable process. Due to the need of the forming process of different products is different, the length is longer, will also be described in the first section 15.2.4. Here, in part forming process including heating and welding a briefly introduction.
For manufactured hot forming methods fitting, in order to meet the requirements on the material deformation in forming process, forming the need for billet heating. Heating temperature usually depending on the material and process need to be addressed.
Pushing elbow or hot elbow forming, usually adopt the method of intermediate frequency or high frequency induction heating, adopt the method of flame heating. This heating mode is synchronized with the elbow or bend forming process of continuous heating, the movement of the tube billet is heated and forming process are completed.
Hot pressing elbow, hot-pressing tee or forging forming, usually adopt the method of reverberatory furnace heating, flame heating method, the method of induction heating or electric heating method, etc. This heating is leading to tube billet heated to the required temperature, to suppress or forging is made into the mould.
B. the welding
Weld pipe fittings including two cases, one is made of welded pipe fitting, for pipe fittings manufacturer, using the forming process of welded pipe forming process of using seamless tube of basic same, pipe forming process does not include the welding process; Another is done by fitting factory the welded pipe forming need process, such as single chip to suppress again after assembling welding elbow, use steel drum welding into the pipe and then to suppress the tee, etc.
In pipe welding methods commonly used with manual arc welding, gas shielded welding and automatic welding.
Manufacturer shall prepare the welding procedure specification to guide the welding work, and should be in accordance with codes for the corresponding welding procedure qualification, to verify the correctness of the welding procedure specification and assess of welding the weld ability.
Welders engaged in pipe welding operations shall be determined by the quality and technical supervision departments of examination and obtain a corresponding qualification certificate shall not engage in relevant steel welding work (according to the regulation of some industries, used for welding pipe fittings to get industry rules in some sectors of welder and welding procedure qualification examination, such as Marine welding pipe fittings to obtain corresponding class welder test and welding procedure qualification).
(3) heat treatment
Heat treatment process is made an important part of pipe fittings. By heating, heat preservation and cooling of the heat treatment step, eliminate the forming process of work hardening, residual stress, the metal deformation defects, etc., make the pipe after forming metal organization, performance, change, return to the front of the deformation processing of status, or make it improved and improve performance.
Commonly used equipment for heat treatment furnace, furnace, etc.; The usual control method for the furnace thermocouple automatically by the sensor is connected to the temperature – time recorder on the control unit.
Different pipe fittings product standards for the regulation of heat treatment is not the same. Not all through the deformation of the pipe fittings are to be heat treatment, usually, for low carbon steel material pipe fitting its final forming temperature is not lower than 723 ℃ (recrystallization temperature), can be heat treatment, not because of the temperature under the condition of its ultimate state of organizations is basically normalizing state, or lower than the temperature higher than 980 ℃ heat treatment should be; Alloy steel or stainless steel pipe fittings whether using cold forming or hot forming, heat treatment shall be.
Routine test of the heat treatment are usually performed by hardness test.
(4) surface treatment
Pipe surface treatment usually adopt sand blasting, shot blasting, polishing, pickling, such as method, to remove rust on the surface of the product, such as scratches, make products to achieve smooth surface, to meet the requirements of the subsequent processing and inspection.
For blasting is adopted to improve the surface fitting, the surface hardness will increase slightly.
Machining is completed in pipe welding ends, structure size and shape tolerance machining process. For some pipe fittings products machining include inner and outer diameter of processing. Cutting processing mainly through special machine tools or general is complete; For pipe size is too large, when the existing machine tool can not meet the requirements of processing, also can use other methods to complete the processing, such as large diameter bend after gas cutting grinding methods.
The appearance of the pipe fittings, dimension inspection often after machining.
Nondestructive testing is the process of testing materials and fittings processing possible defects of important process. The most fitting product standard for nondestructive testing requirements of the rules, but have different requirements. In addition to meet the requirements of product standards and order for nondestructive testing, some of the more stringent quality control of the factory is according to the material, processing technology and quality of internal control regulation on nondestructive testing requirements, in order to guarantee the quality of products.
In the practical work of pipe nondestructive testing qualified grades judgement should be based on orders or specified criteria. For fitting surface basically is the original state of pipe, plate, or forging, the surface quality of pipe nondestructive testing (MT, PT), if there is no clear requirement according to Ⅱ level grade, but no matter how qualified level regulation, for sandwich and this is not easy to determine the depth of crack defect shall be considered not qualified. Internal quality of pipe nondestructive testing (RT, UT,), radiographic testing if there is no clear grading standards should press Ⅱ level (such as weld testing), ultrasonic testing should press Ⅰ level.
In order to prevent the product defects that may occur in the process of heat treatment, fitting the final NDT shall be carried out after heat treatment.
Pipe fittings manufacturer in China NDT commonly used is the JB/T 4730 standard. Do the work in the field of nondestructive testing personnel should be obtained according to the relevant provisions of the corresponding qualifications.
All landowners surface protection
On the surface of carbon steel, alloy steel pipe protection usually adopt the method of painting, after the adoption stainless steel pickling passivation methods (for all surface machining of stainless steel pipe fittings, can need not passivation treatment). The main purpose of the fitting surface protection is anticorrosive, and at the same time to achieve the effect of the product appearance. Usually, the orderer puts forward specific requirements for the surface protection, factory complete protection on the surface of the pipe fittings according to the requirement of the orderer.
Mark is an integral part of product, it is the basis of realizing traceability requirements. Usually, the content and method to the symbol in the product standard for the rules. Pipe symbol content generally includes manufacturer trademarks or name, material grade, specification and other contents required by the order. Marks methods include permanent marks, such as steel, sculpture, electric erosion, etc.; Non-permanent marks, such as spray printing, label, etc.
Other pet-name ruby
Besides the conventional manufacturing process, to control the quality of raw materials, manufacturers should also complete raw material inspection, to ensure that the right of the materials used; To meet the special requirements of goods or materials, but also should be such as microstructure, intergranular corrosion, ferrite, such as inspection and testing, guarantee the use of the product to meet customer requirements.
Source: Zhejiang Yaang Pipe Industry Co., Limited (www.yaang.com)