What is a forging flange?
Forging is a process in which a metal is plastically flowed to form a desired shape. The metal does not change in volume after plastic flow by external force, and the metal always flows to the portion with the least resistance. Forged flange is the best mechanical product in flange products. Its raw material is generally tube blank, and then it is cut and then beaten continuously to eliminate the segregation and looseness in the ingot. The main materials for forged flanges are carbon steel, alloy steel and stainless steel. The forged flange has good pressure resistance and temperature resistance, and is generally suitable for use in high pressure and high temperature working environments. In production, the shape of the workpiece is often controlled according to these laws, and deformations such as upsetting, reaming, bending, and drawing are realized. Forging flange is a combination of forging and stamping. It is a hammer, anvil, punch or a die that applies pressure to the blank by means of a forging flange machine to plastically deform it to obtain the desired shape and size. Forming processing method. In the forging process, the billet as a whole undergoes significant plastic deformation and a large amount of plastic flow; in the stamping process, the billet is mainly formed by changing the spatial position of each part of the area, and there is no plastic flow of a large distance inside. Forging flanges are mainly used for processing metal parts, as well as for processing certain non-metals such as engineering plastics, rubber, ceramic blanks, bricks and composites.
The history of forging flanges
Forging flanges and rolling and drawing in the metallurgical industry are all plastic processing, or pressure processing, but forging flanges are mainly used for the production of metal parts, while rolling, drawing, etc. are mainly used for the production of plates and belts. General metal materials such as materials, pipes, profiles and wires. At the end of the Neolithic Age, humans began to hammer natural copper to make decorations and small items. China has applied cold forging process manufacturing tools in about 2,000 BC. For example, the red copper objects unearthed from the Qijia Cultural Relics Site of Wuwei Huangniangtai in Gansu Province have obvious hammering marks. In the middle of the Shang Dynasty, weapons were made from ferroniobium, and a heating forging process was adopted. The block of wrought iron that appeared in the late spring and autumn is repeatedly heated and forged to extrude oxide inclusions and formed. Initially, people used to forge with a tamper, and later forged the billet by pulling the rope and the pulley to lift the weight and then free fall. After the 14th century, animal power and hydraulic drop hammer forging occurred.
The workpieces from the forged flanges are accurate in size and are advantageous for mass production. The dimensions of die forming, such as die forging, extrusion, and stamping, are accurate and stable. High-efficiency forging machines and automatic forging lines can be used to organize specialized large-volume or mass production.
The forging production process includes forging blanking before forming, forging billet heating and pretreatment; heat treatment, cleaning, calibration and inspection of the workpiece after forming. Commonly used forging flange machinery are forging hammers, hydraulic machines and mechanical presses. The hammer has a large impact speed, which is good for metal plastic flow, but it will produce vibration. The hydraulic machine is forged by static force, which is good for forging metal and improving the structure. It works smoothly, but the productivity is low. The mechanical press has a fixed stroke and is easy to mechanize.
Future forging process will improve the intrinsic quality of forgings, develop precision forging and precision stamping technology, develop forging equipment and forging production lines with higher productivity and automation, develop flexible forging forming systems, develop new forging materials and forging processing methods.
Improve the intrinsic quality of forging flanges, mainly to improve their mechanical properties (strength, plasticity, toughness, fatigue strength) and reliability. This requires a better application of the metal plastic deformation theory; the application of better intrinsic quality materials; correct pre-forging heating and forging heat treatment; more stringent and more extensive non-destructive testing of forgings.
Less and no cutting is the most important measure and direction for the machinery industry to improve material utilization, increase labor productivity and reduce energy consumption. The development of precision forging and precision stamping will be beneficial to the development of less forging blanks, no oxidation heating, and high hardness, wear resistance, long life mold materials and surface treatment methods.
Classification of the main forming methods and deformation temperatures of forging flanges:
Forging according to forming method can be divided into two categories: forging flange and stamping; forging temperature can be divided into hot forging, cold forging, warm forging and isothermal forging.
The hot forging flange is a forging performed above the metal recrystallization temperature. Increasing the temperature can improve the plasticity of the metal, which is beneficial to improve the intrinsic quality of the workpiece and make it less prone to cracking. The high temperature also reduces the deformation resistance of the metal and reduces the tonnage of the required forging machinery. However, there are many hot forging processes, the workpiece precision is poor, the surface is not smooth, and the forgings are prone to oxidation, decarburization and burning. /> Cold forging is forging at a temperature lower than the recrystallization temperature of the metal. The so-called cold forging is usually referred to as forging at normal temperature, and forging at a temperature higher than normal temperature but not exceeding recrystallization temperature. For warm forging pressure. The temperature of the forging pressure is higher, the surface is smoother and the deformation resistance is not large.
The workpiece for cold forging and forming of forging flange at normal temperature has high shape and dimensional precision, smooth surface and less processing steps, which is convenient for automatic production. Many cold forged and cold stamped parts can be used directly as parts or articles without the need for cutting. However, in cold forging, due to the low plasticity of the metal, cracking is likely to occur during deformation, and the deformation resistance is large, and a large tonnage forging machine is required.
Isothermal forging is the constant temperature of the billet throughout the forming process. Isothermal forging is to take advantage of the high plasticity of certain metals at equal temperatures or to achieve specific microstructure and properties. Isothermal forging requires constant maintenance of the mold and billet at a constant temperature, and is only used for special forging processes such as superplastic forming.
Forging flanges can change the metal structure and improve metal properties. After the ingot is hot forged, the original cast loose, pores, microcracks, etc. are compacted or welded; the original dendrites are broken to make the grains fine; at the same time, the original carbide segregation and unevenness are changed. Distribution, so that the organization is even, so that the internal compact, uniform, fine, comprehensive performance, reliable use of forgings. After the forging is deformed by hot forging, the metal is a fibrous structure; after cold forging deformation, the metal crystal is ordered.
Mechanical equipment for forging flanges:
Due to the low production efficiency of hand forging and the forging flange of more than 10 kg weight, it is difficult to manufacture. Therefore, the modern forging workshop is equipped with mechanical forging equipment and has high efficiency.
1. Compressed air hammer
It is mainly used for various basic operations of free forging, and can also perform various manual tread forging. Also called the air hammer.
2, Steam (air) hammer
It is used in a wide range of equipment, free forging and model forging.
3, Hydraulic press
4, Forging hydraulic machine
5. Determination of tonnage of forging hammer and press
There is enough hitting energy to obtain qualified forgings; there is enough space for holding the forging die, mainly the spacing of the guide rails; normal production efficiency can be obtained; and the forging die has a normal service life.
Heating during metal pressure processing
First, the heating specification of the forging flange
1. Heating requirements: The metal is required to obtain the specified temperature under the most uniform heating condition; efforts should be made to minimize the metal oxide scale and minimize the decarburization layer.
2, heating temperature range: over-burning and overheating; initial forging and final forging temperature; heating range; heating rate; heating time determination; temperature stress.
Forging flange production process:
The forging process generally consists of the following steps: selecting high-quality billet blanking, heating, forming, and forging cooling. Forging processes include free forging, die forging and film forging. At the time of production, different forging methods are selected according to the quality of the forgings and the number of production batches.
The free forging productivity is low, the machining allowance is large, but the tool is simple and the versatility is large, so it is widely used for forging a single piece and a small batch of forgings with a simple shape. Free forging equipment includes air hammer, steam-air hammer and hydraulic press, which are suitable for the production of small, medium and large forgings. Die forging has high productivity, simple operation, and easy mechanization and automation. The die forgings have high dimensional accuracy, small machining allowance, and reasonable distribution of the fiber structure of the forgings, which can further improve the service life of the parts.
First, free forging
Basic process: For free forging, the shape of the forging is gradually forged by some basic deformation process. The basic processes of free forging are upsetting, lengthening, punching, bending and cutting.
1. Upsetting Upsetting is an operation process in which the raw material is forged in the axial direction to reduce its height and increase the cross section. This type of process is commonly used for forging gear blanks and other disc-shaped forgings. The ups and downs are divided into two types: all upsetting and partial forging.
2. Pulling out Lengthening is a forging process that increases the length of the blank and reduces the section. It is usually used to produce shaft blanks, such as lathe spindles and connecting rods.
3. Punching A forging process in which a punch punches a through hole or a through hole without using a punch.
4. Bending A forging process that bends the billet into a certain angle or shape.
5. Torting A forging process that rotates a portion of a blank relative to another portion by a certain angle.
6. Cutting The forging process of dividing the blank or cutting the material.
Second, die forging
The die forging is collectively referred to as model forging, and the heated billet is placed in a forging die fixed to the die forging device to be forged.
1. The basic process of die forging The process of die forging: cutting, heating, pre-forging, final forging, punching, trimming, quenching and tempering, shot peening. Commonly used processes are upsetting, lengthening, bending, punching, and forming.
2. Common die forging equipment Common die forging equipment includes die forging hammer, hot die forging press, flat forging machine and friction press.
Generally speaking, forged flanges are of better quality, generally produced by die forging, with fine crystal structure and high strength, of course, the price is also more expensive.
Whether it is cast flange or forged flange, it is a common method of manufacturing flanges. See the strength requirements of the parts to be used. If the requirements are not high, you can also use turning flanges.
What is a casting flange?
Casting is a process in which a liquid metal is cast into a casting cavity adapted to the shape of the part, and after cooling solidification and finishing, a casting or blank having a predetermined shape, size and performance is obtained. The casting blank is nearly shaped to achieve machining-free or small-scale processing, which reduces costs and reduces production time to some extent. Casting flange is a commonly used flange process, which has the advantages of being able to produce more complicated shapes, high production efficiency and low production cost, and is suitable for medium and low pressure pipelines. However, the casting flange has disadvantages such as pores, cracks, inclusions, and poor internal flow lines.
The difference between cast flange and forged flange
Forged flanges generally have lower carbon content than cast flanges and are less prone to rust. Forgings have better streamlined shape, denser structure, better mechanical properties than cast flanges, higher shear and tensile forces than castings, and uniform internal organization of forgings. There are no shortcomings such as pores and inclusions in the casting. However, if the forging process is improper, there will be large or uneven grains, hardening cracks and the like. The cost of forged flanges is higher than that of cast flanges, so the price of forged flanges is much higher than the price of cast flanges.
This analysis is not very good from the appearance analysis, I will tell my analysis experience:
First, the difference in price: the flange sold in the market, the cheapest casting flange, the second casting and forging flange, the price of pure forging flange is higher. This means that you can reach a rough conclusion after going to various stores.
The second is to do a destructive analysis: the flange is cut in half, the cast flange has trachoma, and the pure forged flange has no trachoma. Cast and forged flanges can sometimes be found to have cracks.
The third is to distinguish the size and finish of the flange (this is not generally not visible.): The general tolerance of the casting flange on the market is 1-5mm, the edge chamfer is irregular, and the edge hole burr is not smooth. Because cheap work is not so fine. Forged flanges have small tolerances or positive tolerances.
The distinction between cast steel flange and cast iron flange: The cast iron flange has poor toughness and can be split with a hammer. The material of the flange is generally close to low carbon, and it will be easy to crack if it is welded.
Source: China Stainless Steel Flanges Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)