The use of forgings is very wide, aircraft, automobiles, diesel engine, soldiers, petrochemical, mining and many other aspects are used to forgings.
In many precision mechanical sector forgings are more used.For example, the proportion of forgings used in the aircraft is very high, up to 85% of the aircraft components are forgings.There are also many forging departments on the car, which have the common characteristics of light weight, poor working premise, complex shape, high safety requirements, such as the connecting rod, crankshaft in the car idea, the front beam of the front axle, the rear axle and other security hub parts for the safe operation of the car.Because the scale of forgings is very large and the section is very thick, so the steel in the alloy planning and production skills have many characteristics: in order to ensure the large scale of forgings, large steel needs to be used in the exercise Due to the influence of scale effect, the heat treatment of large forgings has its own characteristics. It is necessary to think about the metallurgical characteristics of large forgings, the instantaneous stress and residual stress in large forgings in heat treatment, the impact of latent heat on heating and cooling process, tempering brittleness and arrangement refinement, etc.There are two kinds of heat treatment in large forgings: top heat treatment and second heat treatment.Top heat treatment is also known as post-forging heat treatment. The primary intention is to prevent the occurrence of white spots, progressive uniformity of chemical composition, refine the arrangement, eliminate mixed crystal appearance, etc., to invent internal arrangement conditions for ultrasonic flaw detection and final function, and to eliminate the reduction of hardness Stress facilitates rough machining invention conditions.If the hydrogen content in steel drops below 2% in the process of exercise, the top heat treatment will first think about grain refinement and elimination of hybrid appearance.The second heat treatment is the final functional heat treatment, its primary intention is to make the rough processed large forgings to achieve the best arrangement required, to ensure the outstanding induction function of large forgings.The second heat treatment usually chooses the first skills of quality adjustment, fire and fire, fire and time and so on.For forgings with high hardness demand, such as large cold roll, the final heat treatment should be selected by quenching and low temperature tempering to meet the application demand.Modify the precautions for heat treatment of large forgings in this section First, large forgings must be slow when heating, section heating is necessary, Austrian insulation should be abundant, usually with a trolley stove dry.Two, low carbon low alloy steel directly quenching salt water, medium carbon alloy structural steel with water and oil double liquid quenching comparison insurance, in the moment of water stay with useful thickness accounting, usually in the skill data book.Three, the new water cooling medium suitable shape simple, data and goods of a single forging, the individual is conditional can be, the condition does not have is still not better.Four, must be the initial condition of a large forging, to detect its microscopic arrangement is necessary, especially wei's arrangement is severe, it is necessary to use the correct The skill of the elimination.
