What are the different features of aluminum hot-forging, warm-forging and cold-forging and what types of forging pieces they each applicable to?
Refer to the processing of blank at a temperature above the recrystallization temperature of the metal. The features are:
1) deformation resistance of the metal is reduced;
2) the cast structure of steel ingot is changed, through recrystallization in the hot-forging process, the casting texture of big particles transforms into the new texture of fine grains, which can reduce the defects of cast structure and improve the mechanical properties of steel;
3) ductility of steel is improved, this is particularly important for some high alloy steels which are brittle and difficult to forge at low temperatures.
It is suitable for metal materials having high deformation resistance and poor plasticity under room temperature.
Refer to the forging process at temperatures around the recrystallization temperature of the metal. The features are: warm-forging is used to get precision forging pieces; the advantage of warm-forging is that it can improve the precision and quality of forging pieces, while is not having the forming force of cold-forging. It is suitable for complex shape small and medium-size precision dies forging pieces of medium carbon steel.
refers to the forging process at temperatures below the recrystallization temperature of the metal. The features are: cold-forging pieces have good surface quality and high dimension accuracy; therefore, cold-forging can replace some kind of cutting processes. Cold-forging can strengthen the metal and improve the strength of metal parts. It is suitable for aluminum and partially alloyed aluminum, copper and partially alloyed copper, low carbon steel, medium carbon steel and low alloy structural steel of small deformation resistance and good ductility at room temperature.
With the screw press machine, how many forging methods are there and what are the features of each method?
The screw press machine is suitable for die forging only, the features are: 1) having the characteristics of both forging hammer and crank press;
2) the per minute stroke is small and the blow speed is low;
3) in a screw press, friction press has the lowest transmission efficiency.
What are the forging features of aluminum, magnesium, titanium and copper alloys and what materials and parts they each suitable for?
Forging features of aluminum alloy: aluminum alloy forging temperature is low and the range of temperature is narrow, tools in contact with aluminum alloy must be smooth, the forging action must be quick and forging process must be in still air; the cracks and folds produced in the forging process should be removed in time, it is hard to punch aluminum alloy forgings. Magnesium alloy is a light metal structure material, it has the feature of high specific strength and high specific stiffness, good damping and electromagnetic shielding properties and dimensional stability, easy to process and recyclable.
In recent years, the use of magnesium alloy is experiencing rapid growth in the automobile, communication, 3C products, transportation, home appliances, new energy, and other fields. Forging features of copper alloy: the copper alloy forging temperature range is narrow (around 150~200℃). Copper alloy is good at conducting heat and electricity, and because of its proper strength, stiffness and ductility, especially its corrosion resistance property in air and seawater, copper alloy makes up a considerable proportion of marine parts.
Currently, copper alloys are widely used for forging various types of high strength and high temperature, high pressure and corrosion-resistant marine shaft, flange and valve body. Forging features of titanium alloys: titanium alloy has high deformation resistance, narrow forging temperature, and high defect sensitivity. It is used on occasions requiring high strength, high stiffness and high reliability such as turbine compressor plate and artificial bone for medical purposes.
There are 3 differences between hot-forging drawing and cold-forging drawing:
I. The advantages are different:
1. Advantages of hot-forging drawing: hot extrusion is not only suitable for forming non-ferrous metals and their alloys and low and medium carbon steels with good ductility and relatively low strength, but also suitable for forming high carbon, high alloy steel with high strength, such as special structural stainless steel, high-speed tool steel, and heat resistant steel.
2. Advantages of cold-forging drawing: producing forgings with cold extrusion technology can save materials, usually output coefficient of cold forging material can reach 80% and above. Take Jiefang Automobile, for example, the output coefficient of materials of piston pin cutting is 43.3%, while that of materials of cold extrusion reaches up to 92%.
For another instance, after changing the manufacturing process of the universal joint bearing sleeve into cold extrusion, the material output coefficient increased to 64% from the past 27.8%. Clearly, using cold extrusion technology to produce mechanical parts can save steel and non-ferrous materials in great quantities.
II. The meanings are different:
1. Meaning of hot-forging drawing: hot extrusion is to heat metal materials to hot-forging temperature for extrusion, which is to heat blank material to a temperature above the recrystallization temperature of the metal for extrusion.
2. Meaning of cold-forging drawing: cold extrusion is the process of making parts under room temperature by placing metal blank in cold extrusion die cavity and putting pressure on the blank with punch pin fixed on the press machine to cause the metal blank to produce plastic deformation.
III. Application objects are different:
1. Application objects of hot-forging drawing: hot extrusion is mainly used for the production of common long pieces of the equal section, profiles, pipes, bars, and various machine parts, stainless steel, nickel-based high-temperature alloy and bars, pipes and profiles of refractory alloy, etc.
2. Application objects of cold-forging drawing: cold extrusion technology is mainly used for cold extrusion of lead, tin, aluminum, copper, zinc and their alloys, low carbon steel, medium carbon steel, tool steel, low alloy steel, and stainless steel, it is also used for causing a certain amount of deformation of bearing steel, high carbon and high aluminum alloy tool steel, and high-speed steel, etc.
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