Casting, hot rolling process and forging process

Hot rolling refers to cold rolling, which is rolling below the recrystallization temperature, and hot rolling is rolling above the recrystallization temperature. In simple terms, a billet is rolled several times after heating, then cut the edge and corrected to become a steel plate. This is called hot rolling. Can significantly reduce energy consumption, reduce costs. When hot rolling, the metal has high plasticity and low deformation resistance, which greatly reduces the energy consumption of metal deformation. Hot rolling can improve the processing performance of metals and alloys, that is, the coarse grains in the casting state are broken, the cracks are significantly healed, the casting defects are reduced or eliminated, the cast tissue is transformed into deformed tissue, and the processing performance of the alloy is improved.

Forging refers to the object produced by forging metal in a red hot state by air hammer or press and other equipment. To put it bluntly, forging is to bake the metal of the object soft and knead it into shape. Forging processing can ensure the continuity of the metal fiber organization, so that the fiber organization of the forging is consistent with the shape of the forging, the metal flow line is complete, the organization is dense, and the mechanical properties are good. The forged objects have high hardness, hard and sharp wear resistance, good texture and good corrosion resistance, which can ensure that the objects have good mechanical properties and long service life. Forgings are objects in which metal is subjected to pressure to shape the required shape or appropriate compressive force by plastic deformation. This force is typically achieved through the use of a hammer or pressure. The forging process builds a refined grain structure and improves the physical properties of the metal. In the actual use of parts, a correct design can make the particle flow in the direction of pressure.

The mechanical properties of castings are lower than those of forgings of the same material. In addition, forging processing can ensure the continuity of metal fiber structure, keep the fiber structure of forgings consistent with the shape of forgings, and complete metal streamline, which can ensure that the parts have good mechanical properties and long service life. Forgings produced by precision die forging, cold extrusion, warm extrusion and other processes are all incomparable castings. Castings are metal forming objects obtained by various casting methods, that is, smelting liquid metal, by pouring, injection, suction or other casting methods into the pre-prepared mold, after cooling by falling sand, cleaning and post-treatment, etc., the resulting object has a certain shape, size and performance.

1. hot rolling means rolling at a temperature above the recrystallization temperature of the metal.

Recrystallization means that when the annealing temperature is high enough and the time is long enough, new grains (recrystallization core) without strain are generated in the fibrous structure of deformed metal or alloy. The new grains grow up continuously until the original deformed structure completely disappears and the properties of metal or alloy also change significantly. This process is called recrystallization, and the temperature at which new grains begin to be generated is called the starting recrystallization temperature, the temperature at which the microstructure is occupied by all new grains is called the final recrystallization temperature. Generally, the recrystallization temperature we call is the arithmetic mean of the beginning recrystallization temperature and the end recrystallization temperature. Generally, the recrystallization temperature is mainly affected by the alloy composition, deformation degree, original grain size, annealing temperature and other factors.

The above is the simple principle of hot rolling in theory. In the actual production of our aluminum processing industry, the main manifestation is that when the ingot is heated to a certain temperature in the heating furnace, that is, above the recrystallization temperature, the rolling is carried out. The determination of this temperature is mainly based on the phase diagram of aluminum alloy, that is, under the most idealized conditions, the determination of heating temperature is based on the temperature at 80% of the solidus of the alloy in the multi-phase diagram, which involves the problem of multi-phase diagrams of different alloys. The determination of heating temperature is based on 80% of the solidus of the alloy. In the implementation of the system, the temperature suitable for the production of the alloy is modified according to the actual production situation and the operation of the equipment.

Features of hot rolling:

1, low energy consumption, good plastic processing, low deformation resistance, work hardening is not obvious, easy to roll, reducing the energy consumption required for metal deformation.

2, hot rolling usually uses large ingots, large pressure under the amount of rolling, fast production, large output, so as to create conditions for large-scale production.

3. Through hot rolling, the cast organization is transformed into the processing organization, and the plasticity of the material is greatly improved through the transformation of the organization.

4, the characteristics of the rolling method determines the existence of anisotropy in the performance of the rolled sheet, one is the material of the vertical, horizontal and high to have obvious performance differences, the second is the existence of deformation texture and recrystallization texture, there is a clear direction in the punching performance.

2. forging processing can ensure the continuity of the metal fiber organization, so that the fiber organization of the forging is consistent with the shape of the forging, the metal flow line is complete, the organization is dense, the permeability is resistant, and the mechanical properties are good. [The forged objects have high hardness, sharpness, wear resistance, good texture and good corrosion resistance, which can ensure that the objects have good mechanical properties and long service life. The application scope of forging is used in the processing of aviation parts, marine parts, diesel engines, petrochemicals, heavy machinery, and high-quality cutting tools.

The theory of 3. casting forming metal liquid forming is often called casting, and the casting forming technology has a long history. As early as more than 5000 years ago, our ancestors were able to cast red copper and bronze products. Casting is the most widely used liquid metal forming process. It is a method of pouring liquid metal into the mold cavity and obtaining a certain shape of blank or part after cooling and solidification.

In the machinery and equipment, the proportion of liquid molding parts is very large, in the machine tool, internal combustion engine, mining machinery, heavy machinery, liquid molding parts accounted for 70% to 90% of the total weight; in the car, tractors accounted for 50% to 70%; in agricultural machinery accounted for 40% to 70%. Liquid molding process can be so widely used, because it has the following advantages:

(1) can produce the cavity, the shape is very complex blank. Such as all kinds of box, machine tool bed, cylinder block, cylinder head and so on.

(2) process flexibility, wide adaptability. The size of the liquid molding is almost unlimited, its weight can be from a few grams to several hundred tons, and its wall thickness can be from 0.5mm to 1m. Industrial where can be dissolved into liquid metal materials can be used for liquid molding. For cast iron with poor plasticity, liquid forming is the only way to produce its blanks or parts.

(3) The cost of liquid molding is low. Liquid molding can directly use waste parts and chips, equipment costs are low. At the same time, the processing allowance of liquid molded parts is small, saving metal.

However, there are many processes in liquid metal forming, and it is difficult to accurately control, so that the quality of castings is not stable enough. Compared with forgings of the same material, due to the loose structure and coarse grains of liquid molding, the internal

It is easy to produce defects such as shrinkage cavity, shrinkage porosity and pores. Its mechanical properties are low. In addition, the labor intensity is large and the conditions are poor. It has excellent mechanical and physical properties. It can have a variety of comprehensive properties with different strength, hardness, and toughness. It can also have one or more special properties, such as wear resistance, high temperature and low temperature resistance, and corrosion resistance.

The weight and size range of castings are very wide, the lightest weight is only a few grams, the heaviest can reach 400 tons, the thinnest wall thickness is only 0.5mm, the thickest can be more than 1 meter, the length can be from a few millimeters to more than 10 meters, can meet the requirements of different industrial sectors.

Use

The use of castings is very extensive, has been applied to the hardware and the entire machinery and electronics industry, and its use is becoming a growing trend. Specifically used in construction, hardware, equipment, construction machinery and other large machinery, machine tools, ships, aerospace, automobiles, locomotives, electronics, computers, electrical appliances, lamps and other industries, many of which are exposed to ordinary people all day long, but do not understand metal objects.