P91 alloy pipe is rolled from a solid pipe blank after being perforated.
1. Production and manufacturing methods
According to different production methods, it can be divided into hot-rolled pipes, cold-rolled pipes, cold-drawn pipes, extruded pipes, etc.
1.1. Hot-rolled P91 alloy pipes are generally produced on automatic pipe rolling units. The solid tube blank is inspected and surface defects are removed, cut into the required length, centered on the perforated end of the tube blank, and then sent to the heating furnace for heating and piercing on the punching machine. It continues to rotate and advance during piercing holes. Under the influence of the rollers and the end, the tube blank is hollow gradually, which is called gross pipe. Then it is sent to the automatic pipe rolling machine to continue rolling. Finally, the wall thickness is evened by the leveling machine, and the diameter is determined by the sizing machine to meet the specification requirements. The use of continuous pipe rolling units to produce hot-rolled P91 alloy pipes is a more advanced method.
1.2. If you want to obtain seamless steel pipes with smaller size and better quality, you must use cold rolling, cold drawing or a combination of the two. Cold rolling is usually carried out on a two-roll mill, and the steel pipe is rolled in an annular pass composed of a variable cross-section circular groove and a fixed conical head. Cold drawing is usually performed on a 0.5 to 100T single-chain or double-chain cold drawing machine.
1.3. The extrusion method is to place the heated tube blank in a closed extrusion cylinder, and the perforation rod and the extrusion rod move together to make the extrusion part extruded from the smaller die hole. This method can produce steel pipes with smaller diameters.
2. Purpose
2.1. P91 alloy pipe is widely used. General-purpose P91 alloy pipes are rolled from ordinary carbon structural steel, low alloy structural steel or alloy structural steel. They have the largest output and are mainly used as pipes or structural parts for conveying fluids.
2.2. They are supplied in three categories according to different uses: a. Supplied according to chemical composition and mechanical properties; b. Supplied according to mechanical properties; c. Supplied according to hydraulic pressure test. If the steel pipes supplied according to categories a and b are used to withstand liquid pressure, they must also undergo a hydrostatic test.
2.3. Special-purpose P91 alloy pipes include P91 alloy pipes for boilers, P91 alloy pipes for geology, and seamless steel pipes for petroleum.
Classification of 3P91 alloy pipe
The main alloying elements of alloy pipes are silicon, manganese, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, aluminum, copper, boron, rare earth and other alloy steel pipes. In addition to iron, carbon and a small amount of indispensable materials, alloy steel pipes contain In addition to the avoided elements of silicon, manganese, phosphorus and sulfur, it also contains a certain amount of alloying elements. The alloying elements in steel include silicon, manganese, molybdenum, nickel, chromium, alum, titanium, niobium, boron, lead, rare earths, etc. One or several types of steel are called alloy steel. Each alloy steel system varies with their respective resource conditions, production and use conditions. Foreign countries have developed nickel and nickel steel systems in the past, but our country has discovered that silicon, manganese, Alloy steel systems based on vanadium, titanium, niobium, boron, lead and rare earths account for about more than ten percent of the total production of steel. They are generally smelted in electric furnaces. Alloy steel pipes can be divided into 8 major categories according to their uses. categories, they are: alloy structural steel pipes, spring steel pipes, bearing steel pipes, alloy tool steel pipes, high-speed tool steel pipes, stainless steel pipes, heat-resistant non-flaking steel pipes, electrical silicon steel pipes PC/ABS have good formability and can process large-scale automobiles Components, such as automobile fenders, have a high cost performance. Alloy steel pipes are made of iron-carbon alloy steel pipes by adding an appropriate amount of one or more alloy elements to ordinary carbon steel. Classification of steel pipes: steel pipes are divided into P91 alloy pipes and welded steel pipes. Steel pipes, etc.
3. Specifications and appearance quality
P91 alloy pipe is in accordance with GB/T8162-87
3.1. Specifications: The outer diameter of hot-rolled pipe is 32~630mm. Wall thickness 2.5~75mm. The outer diameter of cold rolled (cold drawn) pipe is 5~200mm. Wall thickness 2.5~12mm.
3.2. Appearance quality: The inner and outer surfaces of the steel pipe must not have cracks, folds, roll folds, separation layers, hair lines and scarring defects. These defects should be completely removed, and the wall thickness and outer diameter should not exceed negative deviations after removal.
3.3. Both ends of the steel pipe should be cut at right angles and burrs should be removed. Steel pipes with wall thickness greater than 20mm are allowed to be cut by gas cutting and hot sawing. It is also possible not to cut the head after agreement between the supply and demand parties.
3.4. The "surface quality" of cold-drawn or cold-rolled precision P91 alloy tubes refers to GB3639-83.
4. Chemical composition inspection
4.1. The chemical composition of domestic P91 alloy pipes supplied according to chemical composition and mechanical properties, such as No. 10, 15, 20, 25, 30, 35, 40, 45 and 50 steel, shall comply with the regulations of GB/T699-88. Imported P91 alloy pipes are inspected according to relevant standards stipulated in the contract. The chemical composition of 09MnV, 16Mn, and 15MnV steel should comply with the regulations of GB1591-79.
4.2. For specific analysis methods, please refer to the relevant parts of GB223-84 "Chemical Analysis Methods for Steel and Alloys".
4.3. The analysis deviation refers to GB222-84 "Permissible deviations of chemical composition of samples and finished products for chemical analysis of steel".
Welding process of 6P91 alloy pipe[1]
In order to increase the argon gas protection zone and enhance the protective effect, a large-diameter welding gun porcelain nozzle can be used to increase the argon gas flow rate of the welding gun. When there is splash attached to the nozzle that obviously hinders the flow of argon gas. Splash must be removed or the nozzle must be replaced. When the tungsten tip is contaminated or irregular in shape, it must be repaired or replaced. The tungsten pole should not stick out of the nozzle. The control of welding temperature is mainly the control of welding speed and welding current. The test results show that high current and fast welding can effectively prevent the occurrence of pores. This is mainly due to the faster penetration of the weld during the welding process, the shorter the heating time of the molten metal and the less chance of absorbing gas.
Seamless steel pipe classification
The types of seamless steel pipes are as follows: (1) Seamless steel pipes for general structures and mechanical structures (GB8162-87) (2) Seamless steel pipes for low and medium pressure boilers (GB/T3087-1999) (3) Seamless steel pipes for high-pressure boilers ST45.8/111 (GB5310-85) (4) Seamless steel pipe for conveying fluids (GB/T8163-1999) (5) Cold-drawn or cold-rolled precision seamless steel pipe (GB3639-83) (6) Steel pipe for geological drilling (YB235-70) (7) Oil drilling steel pipe (YB528-65) (8) Seamless steel pipe for precision inner diameter of hydraulic cylinder barrel (GB8713-88) (9) Special seamless steel pipe for fertilizer (GB6479-86) (10) Ships Pipe (GB5312-85) (11) Petroleum cracking pipe (GB9948-88) (12) Various alloy pipes 16Mn 27SiMn 15CrMo, 35CrMo 12CrMov 20G 40Cr, 20Gr, Gcr15
