C45 quenched and tempered steel
C45 quenched and tempered steel
C45 steel is carbon structure steel, hot and cold processing performance is good, mechanical performance is better, and low price, wide source, so it is widely used.Its biggest weakness is the hardenability is low, large cross section size and high requirements of the workpiece is not suitable.
C45 steel quenching temperature in A3+(30~50) ℃
It is generally taken upper limit.The high quenching temperature can accelerate the heating speed, reduce the surface oxidation, and improve the efficiency.In order to make the austenite of the workpiece uniform, it needs enough time for insulation.If the actual furnace load is large, it is necessary to appropriately extend the insulation time.
Otherwise, the phenomenon of insufficient hardness may occur due to uneven heating.However, if the insulation time is too long, the grain size will also appear, serious defects of oxidation and decarburization, affecting the quenching quality.
heating and holding time should be extended by 1/5.
Because C45 steel hardenability is low, so should use cooling rate of large 10% brine solution.After the workpiece enters the water, it should be quenched thoroughly, but not cold. If the workpiece cools thoroughly in the brine, it may cause the workpiece to crack. This is because when the workpiece cools to about 180℃, the austenite rapidly changes to martensite, resulting in excessive tissue stress.Therefore.
When the quenching workpiece quickly cold to the temperature of the region, should take a slow cooling method.Because the water outlet temperature is difficult to grasp, must operate by experience, when the shaking of the workpiece in the water stops, the water outlet air cooling (such as oil cooling is better).In addition, the workpiece into the water should not be static. It should be in accordance with the geometric shape of the workpiece, regular movement.Static cooling medium plus stationary workpiece, resulting in uneven hardness, uneven stress and workpiece deformation, even cracking.
Hardness of C45 steel quenched
Hardness of C45 steel quenched parts should reach hrc56-59, and the section may be lower, but not lower than HRC48, otherwise, it means that: the workpiece has not been completely quenched, sostenite and even ferrite may appear in the tissue, which is still retained in the matrix through tempering, so as to reach the purpose of tempering.The tempering temperature of 45 steel after quenching is usually 560~600℃, and the hardness is HRC22~34.
Because the purpose of tempering is to obtain comprehensive mechanical properties, the hardness range is relatively wide.But the drawing has the hardness request, must adjust the tempering temperature according to the drawing request, in order to ensure the hardness.If some shaft parts require high strength, high hardness requirements;And some gear, with keyway shaft parts, because after conditioning, but also milling, insert processing, hardness requirements are lower.
About tempering insulation timeaccording to the hardness requirements and the size of the workpiece, we believe that the hardness after tempering depends on the tempering temperature, and the tempering time is not relevant, but must be back through, generally the tempering insulation time of the workpiece is always more than an hour.
The commonly used alloy tempered steels are divided into 4 categories according to hardenability and strength:
(1) quenched steel with low hardenability;
(2) quenched tempered steel;
to be continued
Ms Sharon Wan
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