This paper focuses on the analysis of the fracture, management and use factors caused by the poor heat treatment materials, in order to strengthen the management of technology and lifting appliances and ensure the safety of the enterprise.
Cause analysis and prevention of fracture in heat treatment
The classification of heat treatment cracks: non quenched crack surface crack, surface edge crack; quenched crack longitudinal crack (tissue stress type), arc crack (local tensile stress type), large workpiece quenched crack (longitudinal and transverse), edge surface crack (local tensile stress type), fracture, the second type of stress crack.
Methods for checking cracks:
The simplest and most common way to check whether the parts have cracks is to directly observe the parts with naked eyes after sandblasting or use a magnifying glass to observe the surface of the parts. When no crack can be seen with eyes or magnifier, oil immersion flaw detection method can also be used. Immerse the parts in kerosene, gasoline and other oil, take out the parts later and wipe them with cotton yarn, then apply lime powder or other white powder, if there is crack, oil will seep out in the white part. Experienced inspectors can also use percussion method to check whether there is crack, that is, use a small hammer and other light percussion parts, if there is a clear metal sound, the tail sound is long, indicating that there is no crack; otherwise, if there is a heavy noise, there is a crack. Magnetic flaw detection and fluorescent flaw detection can also be used to check whether the parts have cracks.
Precautions:
(1) Reduce the heating temperature of quenching and shorten the holding time.
(2) Increase the temperature of the cooling medium from 0 ℃ to above 15 ℃.
(3) Increase the concentration of quenching medium, add water glass, and adjust to the upper limit of specified process value.
On 2018-08-08 11:45:46
