What Are Our Concerns About Bearings（55）

Q1:20# steel for flange, must it be forged?

A:Depending on the pressure grade of your flange, if greater than or equal to PN2.0mpa, it must be forged or cast, the standard is not allowed to directly use steel plate.  

Check two standards, one is allowed to use plate, one is not allowed, in order to facilitate the manufacturing process, can use plate, production organization is more convenient.  

Q2:JIS B2316-1997 Forgings standard?

A:Steel sleeve welded pipe joint for piping

The standard only provides for steel, and does not stipulate that it must be forged, so it cannot be said to be a forgings standard.

Q3:Are the forgings of the same material and thickness the same mechanical properties as sheet metal?

A:Take S30403 as an example:

Forgings: NB/T47014 standard tensile/yield/elongation respectively: 480/175/35

Sheet: ASTM A276 tensile/yield/elongation: 485/170/40, respectively.

Q4:Gb12459-2005 standard is forgings or castings?

A:Steel butt-welded seamless pipe fittings

It is the size of the specific pipe fitting that is required. There is no specific description of whether the material should be cast or forged. The specific requirements depend on the customer’s requirements.

Q5:What is the difference between flat forging machine and hot upsetting machine?

• A:Under the action of external force, the metal billet produces plastic deformation in the mold and fills the mold chamber (mold cavity) to obtain the desired shape and size of the forging method.  Most metals are die forged in a hot state, so die forging is also called hot die forging.  Compared with free forging, die forging can forge a more complex shape, more accurate size forgings, production efficiency is relatively high, can produce a large number of shape and size are basically the same forgings, easy to use automatic machine tools and automatic production lines in the subsequent cutting process.  After die forging, the forging is formed with directional fiber structure, that is, streamline.  The mechanical properties of forgings can be significantly improved by selecting reasonable die forging process and die to make the distribution of streamline consistent with the shape of parts.  But die forging needs special die, die must be made of high quality alloy tool steel, mold bore shape complex, high precision requirements, large processing, long production cycle, expensive.  Therefore, die forging is generally suitable for mass production, or for batch is not large, but the shape and performance of the forgings have higher requirements.  
• Die forgings have high precision and small machining allowance. The decision of machining allowance needs to consider the manufacturing accuracy of the die and its wear in use, the cold shrinkage and surface oxidation of metal, the metal flow and filling state, the required slope of forging, fillet and forging deviation, and the allowance required by cutting, etc.  In actual production, forging processing allowance is selected according to the standard.  The use of special precision forging technology, strict control of local tolerance forgings, no cutting allowance, no cutting, is one of the development direction of modern die forging technology.  
• Die forging is usually divided into hammer die forging, hot die forging press die forging, screw press die forging, hydraulic press die forging, flat forging machine die forging and electric upsetting, etc.  
• Hammer die forging is widely used in production. The forging die is divided into two parts, which are fixed on the hammer head and anvil seat respectively. The upper die on the hammer head is struck on the lower die of the anvil seat (without anvil seat die forging hammer is struck on the anvil) so that the forging takes shape.  The billet often goes through a number of billet processes, for which the forging die is provided with a corresponding number of die bore.  When forging, the billet is heated to the initial forging temperature (see forging billet heating), and then the forging billet is moved to the corresponding die chamber according to the process by manual, which is hit by the forging hammer in turn, and finally formed in the final forging die chamber.  Typical hammer die forging goes through 6 processes (no upsetting process is shown in Figure 1[Basic process of hammer Die]).  ① Upsetting: used to reduce the height of the billet, increase the cross-sectional area.  (2) drawing: the billet is flipped around the axis and sent along the axis to reduce the local section of the billet and extend the length of the billet.  (3) rolling: when the operation is only turned over without feeding, the local section of the billet can be increased and the appearance of the whole billet is round and smooth.  Bending: used to change the shape of the billet axis.  (5) pre-forging: improve forging forming conditions, reduce the wear of the final forging die bore.  The final forging: the final forging shape, determine the shape and precision of the forging.  The final forging die bore is provided with a flapping groove around it.  
• Die forging hammer strike speed, impact energy is large, the weight of the strike can be controlled by the operator at will, so the adaptability of forgings can be forged below 1 kg to about 200 kg of various complex shape forgings, such as engine connecting rod, crankshaft, automobile universal joint, front beam and all kinds of gears.  Hammer die forging has high productivity and less equipment investment.  Disadvantages are vibration and noise, operating technology is not easy to master, poor labor conditions, labor intensity.  In addition, the die hammer generally does not have a ejection device, forgings need a large die forging slope, the life of the die is low.  
• Hot die forging press Die forging hot die forging press is generally crank mechanical press.  Its vibration and noise than the hammer die forging, the operation technology is relatively easy to master, high productivity, easy to use manipulator to achieve automatic production.  Hot die forging press has good rigidity, high slider guide precision, forging ejection device, can use smaller die forging slope.  The second Automobile factory of China has automatic forging production line with 120,000kn hot die forging press, equipped with roll forging press, edge cutting press, torsion press, correction press, manipulator and transmission device, which can forge 60 ~ 90 automobile crankshafts or front beams per hour.  The stroke of hot die forging press is fixed, and it can not replace the roll forging machine or other equipment to complete the corresponding blank operation, nor can it use the impact inertia like forging hammer to form forging parts.  In order to make the forgings full of die bore, it is often necessary to increase the number of pre-forging, so that the blank gradually approaches the shape of the forgings in several die bore, so the structure of the die is more complex.  Die forging of hot die forging press is suitable for mass production.  
• Die forging screw press is characterized by large impact inertia of forging hammer, good guidance of mechanical press, ejection device, no need for steam power, is a universal die forging equipment.  It has only a small amount of flying edge, the mold Angle is very small, forging by the push rod will be pushed out of the forging.  For small and medium forgings single die chamber forging effect is very good, especially upsetting forged valve, bolt and other rod parts of the head.  Forgings with complex shapes can be preformed on other equipment and then finished on the screw press.  
• Hydraulic press die forging hydraulic press working speed is low, stroke is large, high pressure, and can be adjusted, there is a top out device;  If necessary, pressure can also be applied from several directions (multi-directional die forging hydraulic press).  The pressure of giant hydraulic press reaches hundreds of thousands of thousands of cattle, and the working platform area reaches dozens of square meters.  It is suitable for forging large steel, titanium alloy, aluminum alloy and magnesium alloy forgings, especially large aviation forgings, such as aircraft frame, landing gear girder.  Multi-directional die forging hydraulic press is suitable for die forging various multi-hollow complex forgings, such as high pressure machine housing, valve body and three-fork, four-fork pipe joints, etc. (Figure 2 [multi-directional die forging diagram]).  
• Flat forging machine die forging, also known as flat forging, is a common method for upsetting the head of long rod, pipe and rod to manufacture annular parts with through-hole, such as the flange part of long shaft, bearing ring and so on.  FIG. 3 [Flat forging die forging process] shows a typical flat forging die forging process.  FIG. 4 [Flat forging die and its movement process] shows the flat forging die and its movement process.  When working, the movable die moves, clamping the heated bar material at the end, and then upsetting is carried out by the multi-station punch fixed on the main slide block, so that the metal fills the die bore.  If the length of the deformed part of the bar is more than 3 times of the diameter of the bar, the bar end must be aggregated one or more times before pre-forging and final forging to avoid bending or folding during upsetting.  Forgings with blind holes are first forged and then separated from the bar during punch punch.  Flat forgings generally do not produce flaps or only produce smaller flaps, so the utilization rate of the material is high, but the bar needs to be clampped after forging, so the bar is required to have a smaller diameter tolerance.  
• The die forging process (FIG. 5[Electric upsetting]) in which the end of the bar is energized and the resistance of the bar itself is used for contact heating. At the same time, the axial pressure is applied to the end of the bar, so that the end gradually becomes hot and coarse until it is filled with the die bore and formed.  This method combines heating and deformation in a machine at the same time, so forming good, high efficiency, mainly used for internal combustion engine valve forming.  
• With the progress of technology, in addition to the traditional die forging method in continuous improvement, there are many precision high-speed die forging new technology and new equipment.  For example, with hydraulic screw press, only a small amount of grinding allowance is left on the blade surface.  Precision die forging gear, tooth shape can no longer be machined;  Multi-station automatic hot heading machine forming rods or discs of rods are fed, heated, cut into a blank of fixed length, and then formed in 3 or 4 stations.  The whole process is carried out automatically, and about 3kg of gear billets and bearing ring billets can be forged in 40 ~ 70 pieces per minute.  High speed hammer forging is die forging with special equipment.  Extrusion and cold heading also belong to die forging in a broad sense  
• Hot stamping refers to the material processing than thick material punching, blanking, bending, etc.;  Hot upsetting extrusion refers to extrusion type such as tool wrenches, screw caps, nuts and so on