1. The reasons for low hardness after quenching are:
(1) Low quenching temperature
(2) The quenching water pressure is low, the water volume is not enough, and the cooling speed is not enough
(3) Surface decarburization
(4) Steel has poor hardenability
(5) Too much retained austenite
Preventive or precautionary measures:
(1) Increase the quenching heating temperature by adjusting voltage or mechanical parameters
(2) Increase the water pressure or water temperature and increase the cooling speed
(3) Select materials with composite requirements
(4) Use materials with good hardenability
(5) Choose a medium with good cooling performance to reduce retained austenite or increase the tempering temperature
2. Uneven hardness after quenching:
(1) The water distributor is reversed or clogged
(2) The sensor, sprinkler and roller are not concentric
Preventive or precautionary measures:
(1) Reduce the water pressure or the angle of the water spray
(2) Adjust the sensor and sprinkler
3. The soft spot at the lower end of the roller is too wide:
(1) The starting position of the sensor is too high
(2) The sensor, sprinkler and roller are not concentric
Preventive or precautionary measures:
(1) Lower the power outage position of the sensor
(2) Increase water spray
4. The soft belt at the upper end of the roll is too wide:
(1) The sensor is powered off too early
(2) The sensor stop position is too low
Precautionary or precautionary measures: Raise the power outage position of the sensor
5. The upper edge of the roller falls off (the edge falls off):
(1) The sensor power outage is too late
(2) The sensor stop position is too high
Measure:
(1) Lower the sensor power outage position
(2) Lower the sensor power outage position
(3) Add protective ring
6. Quenching deformation or cracking:
(1) The temperature difference between the surface or core during quenching is too large, causing internal stress.
(2) The quenching temperature is too high, the heating speed is too fast, the holding time is too long, and the cooling is too intense
(3) Decarburization occurs during the heating process and tempering is not timely.
(4) The interface difference is large and the structural design is unreasonable, resulting in excessive quenching stress and exceeding the strength limit of the material.
(5) Fiber cracks in high-carbon martensite expand into macro cracks
(6) The quality of raw materials is poor and the hydrogen content exceeds the standard.
(7) Improper forging process
Measure:
(1) Select materials correctly and try to use materials with less tendency to deform and crack.
(2) Optimize quenching process parameters, fully preheat and select cooling medium
(3) Use paint to protect it during heating to avoid surface oxidation and decarburization, and temper it immediately after quenching.
(4) Properly design the roll mechanism to minimize the thickness disparity and asymmetric shape of the roll section.
(5) Reasonably formulate the heat treatment process and temper in time after quenching to eliminate stress
(6) Select appropriate raw materials and conduct sufficient dehydrogenation treatment
(7) Strictly implement forging process parameters
