Manufacturing process of valve body forging with side flange
At present, high and medium pressure valves with flange are widely used in petrochemical system. The valve body is the main part of the valve. According to American Petroleum Association (API) specification for wellhead and Christmas tree equipment, the oil valve body is often required to work under high pressure, high corrosive gas and high air tightness conditions, and the working conditions are harsh. For a long time, there are welding, casting and forging processes for valve body with flange. The welding process is generally the flange part welding of the main body forging of the valve body. Its disadvantage is that the weld seam is easy to produce pores and hot cracks, and the welding process is complex and the production efficiency is low. The disadvantage of casting process is that there are many defects such as blowhole, inclusion, porosity and crack inside the casting. In view of the rated working pressure of valve body used in petrochemical industry is 13.8mpa-138mpa. In view of the defects of insufficient air tightness, unsatisfactory pressure bearing and low qualified rate of finished products in welding and casting processes, forging process is more and more used to produce petroleum valve body forgings.
At present, the valve body with flange is usually forged separately, and then the valve body and flange are connected by welding. However, the welding parts are easy to have defects, which will affect the overall quality of the valve. Some manufacturers also adopt the membrane forging process of step forging and local forming. The disadvantage of this process is that the operation process is various, and the separation of materials is accurate in the process of blank making, otherwise the forging is easily scrapped However, due to the serious damage of metal flow line, the mechanical performance of valve body is extremely unstable, and the multi-directional die forging technology can solve the above problems. Through one forging, forgings with complex structure, boss or hollow can be formed.
Therefore, this paper describes the manufacturing process of multi-directional die forging technology for a valve body with side flange. The forging of valve body with complex shape and inner hole can be forged in one fire, and the forging streamline is complete. Then the necessary post forging treatment is carried out to ensure the overall performance of the valve body, which provides a new idea for the application of this or similar valve body manufacturing process.
Table of Contents
In this paper, the manufacturing process of Q345B valve body with side flange is studied. The valve body parts are mainly used in petrochemical industry. The traditional process is directly processed by bar. The mechanical performance requirements are shown in Table 1.
Table.1 mechanical property requirements of forgings
|Parameter||Tensile strength / Mpa||Yield strength / Mpa||Elongation /%||Impact energy / J|
It can be found from Figure.1 that the inside of the valve body is composed of two vertical and horizontal holes. The projected area of the vertical plane of the valve body is larger than that of the horizontal plane. The volume of the side flange of the valve body is large, which is difficult to be forged. The structure of the valve body is complex and irregular. Therefore, multi direction die forging technology is proposed to be used in forging process, and heat treatment is carried out after forging to ensure the mechanical properties of valve body meet the requirements.
According to the shape of parts, performance requirements and the capacity of hydraulic press, the structural form of valve body forging shown in Fig. 2 is designed and manufactured on 40Mn multi direction die forging hydraulic press and auxiliary equipment. The main technological route is determined as follows: 1) computer numerical simulation → 2) preparation for returning materials → 3) heating for returning materials → 4) die preparation → 5) multi direction die forging forming → 6) nondestructive testing of forgings → 7) heat treatment of forgings → 8) shot blasting of forgings, among which 1) and 2) are the key control links.
Fig.1 part diagram
Fig.2 structural diagram of valve body forging with side flange
Computer simulation of forging
According to the requirements of forming process parameters of valve body forging, the three-dimensional modeling of blank, upper die, lower die and punch is shown in Fig.3 by using SolidWorks software. The 3D model format is transformed and imported into DEFORM-3D software to simulate and analyze the forging forming process.
Fig.3 three dimensional drawing of forging and die
1-vertical punch 2-upper die 3-forging 4-horizontal punch 5 lower die
In the process of finite element simulation, the bar is selected as the blank, and the initial forging temperature is 1150 ℃ and the die temperature is 200 ℃. The blank is set as plastic body, and the die is set as rigid body. The rigid viscoplastic flow model is used in the forming process. The shear friction model is selected between the blank and the module, and the friction factor is 0.15.
In the process of forging with multi-directional die forging technology, the punch can exert pressing force on the blank in the die from all directions, and the movement sequence, travel distance and displacement of the punch can be arbitrarily combined. This combination has great influence on forging effect, load and die life. According to the analysis of the structure and shape of the valve body forging, the flange is easy to be filled and incomplete, so it is difficult to form. Therefore, the multi-directional die forging process is as follows: upper and lower die closing → horizontal punch movement → vertical punch movement → reset.
In the process of multi-directional die forging, the movement sequence of punch affects the material flow and displacement field in the forging. The diameter of the horizontal hole cavity of the valve body part is small. The force on the punch is large when forming the horizontal hole cavity by simulation calculation, which is beyond the capacity of the equipment. Moreover, the horizontal punch has large deformation, which is difficult to draw and easy to fracture. Therefore, by adjusting the displacement of the vertical punch, the blank can be orderly filled with the cavity under a small deformation force, and the internal tearing and surface folding of the forging can be avoided
To sum up, the blank is placed horizontally in the lower mold cavity, the upper and lower dies are closed, and then the left and right horizontal punch jointly extrude and move to specify the displacement, as shown in Fig. 4B. During the whole process, the metal flows to the side flange first, and a drum is formed in the middle of the blank in the vertical direction, as shown in FIG. 4A and 4B. After the horizontal punch reaches the designated point, the outer fillet of the flange and the lower bottom surface of the forging are not fully filled with gold At this time, the blank is extruded by the vertical punch movement to make the metal fill the mold cavity, as shown in Fig. 4D. The simulation results show that the forging has good forming effect without defects. The required clamping force is 20Mn, the vertical punch pressing force is 3.2mn, and the horizontal punch pressing force is 5.6mn. Through comparison, the selected forging equipment capacity can meet the design requirements.
Blank and die
The technical requirements of the rolling bar with a diameter of 145mm are in line with the requirements of GB/T 1591 and GB/T 702. The sawing machine is used for blanking. The oxidation burning rate and sawing loss should be considered when calculating the cutting weight, and the blanking weight should be accurately controlled in 76.2-76.5kg.
|(a) early||(b) middle|
|(c) late||(d) end|
Fig. 4 metal flow process
According to the factory conditions, the billet can be heated by chamber furnace or medium frequency furnace. The heating temperature is 1200 ℃, and the initial forging temperature is above 1150 ℃. Descaling must be carried out after heating.
The preheating temperature of the mould should be above 200 ℃, and the mould lubricant should be water-based graphite emulsion.
Multi direction die forging
The multi-directional die forging process of the forging with side flange is obviously different from that of the ordinary tee forgings. Therefore, the upper and lower dies, vertical and horizontal punch adopt pressure control. In the forming process, the pressure of horizontal cylinder and vertical cylinder is adjusted according to the situation to obtain the best process parameters. While the side flange is formed by horizontal punch, the synchronization of symmetrical punch in horizontal direction should be ensured during the forming process The specific forming process is as follows: ① upper and lower die closing → ② the left and right horizontal punch moves to the specified stroke position → ③ the vertical punch moves to the specified stroke position → ④ the vertical punch resets → ⑤ the horizontal punch resets → the upper die resets → ⑦ the forging demoulding → and (8) enters the next cycle
The main control parameters of multi direction die forging are shown in Table 2.
Table.2 main forming control parameters
|Forming process||Control mode||Pressure / Mpa||Initial point||Termination point||Displacement / mm|
|Upper mode downlink||Control displacement||一||0||390||390|
|Upper mode downlink||Control pressure||50||390||一||一|
|Horizontal punch movement||Control displacement||一||0||290||290|
|Horizontal punch movement||Control pressure||50||290||一||一|
|Vertical punch movement||Control displacement||一||0||435||435|
|Vertical punch movement||Control pressure||15||435||一||一|
|Reset and demoulding|
Post treatment of forgings
After cooling, 100% ultrasonic testing was carried out on the outer surface of forgings according to GB / T 6402, and no defects were found. After normalizing at 910 ℃ and holding time 5ho, the surface of forgings shall be shot blasted to remove oxide skin. The main parameters of shot blasting are shown in Table 3.
Table.3 main parameters of shot blasting
|Parameter||Diameter of steel shot / mm||Ejection velocity / m, min||Shot blasting time / min|
According to the process plan, the trial production of this kind of products was carried out on the 40Mn multi direction die forging hydraulic press. According to the actual structure and shape of the forging, the forging forming results were basically consistent with the simulation results. Qualified products were forged in one fire, and the flange was fully filled. After inspection, the mechanical properties of the products were better than the design requirements. See Table 4, and the appearance quality of forgings was good, as shown in Figure 5.
Table.4 mechanical properties of forgings
|Parameter||Tensile strength / Mpa||Yield strength / Mpa||Elongation /%||Impact energy / J|
Fig.5 trial production
On the basis of trial production, small batch production was carried out, and the first pass rate reached 91%. At the same time, in the design process, the stress of the punch in the metal deformation was fully considered, the use of small pressing force, no vertical punch metal accumulation, no obvious groove scratch in the mold cavity, improved the service life of the mold.
- (1) The forming process of valve body forging with side flange is simulated by computer numerical simulation. The law of metal flow, stress distribution and deformation are analyzed, which provides technical support for practical production
- (2) According to this scheme, qualified valve body forgings with side flange can be manufactured, which is in good agreement with the numerical simulation results
- (3) The valve body manufacturing technology based on multi-directional die forging process can be forged in one fire. The forging has excellent mechanical properties and appearance quality, and can save energy and materials
- (4) Through the reasonable movement sequence, displacement and pressing force of die and punch, the forging of valve body with flange can be formed.
Author: Song Changzhe
Source: Network Arrangement – China Valve Supplier: www.epowermetals.com
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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