The agricultural diesel engine forging is one kind of power machinery. The varieties of forgings have crosshead pin shaft, main journal, piston head, connecting rod, crankshaft drive gear, connecting rod, cylinder head, gear ring, intermediate gear and fuel pump body.
The quenching treatment of the agricultural diesel engine forgings
The products are tempered after quenching and normalizing treatment. Tempering is the last process of heat treatment. There four kinds of main purpose of tempering.
1. Eliminate or reduce the internal stress produced during quenching and normalizing cooling.
2.The stable tempering structure is obtained to meet the required technical index of the mechanical property.
3.Further remove the hydrogen in the forging or make the distribution more reasonable.
4.As mentioned earlier, the core organization transformation in the cooling process is further completed.
In the production process of agricultural diesel engine forgings, to meet the different hardness and other mechanical properties of large forgings, different temperature tempering needs to be selected after quenching. According to the different tempering temperature, the tempering process is often divided into low temperature tempering in the production. Tempering temperature is between 150 - 250 ℃. Its purpose is to stabilize or reduce the quenching stress, reduce the brittleness of steel and keep the high hardness of steel.
The surface quenching of agricultural diesel engine forgings should be tempered at low temperature, and the temperature is about 130 degrees to 140 degrees. In the middle tempering, the tempering temperature is generally between 350 degrees to 500 degrees, so that the higher elastic limit can be obtained, and has the high toughness.
The stress relieving of the agricultural diesel engine forgings
There is large internal stress in the general welded parts. In order to eliminate the internal stress of these parts and to achieve the purpose of stable shape and geometric size, high (medium) temperature tempering treatment is often needed. Some factories call the tempering of such parts as artificial ageing treatment, sometimes referred to as low temperature annealing.