QPQ is abbreviation of quench-polish-quench. QPQ is a kind of metal surface modification technology, with high corrosion resistance,high wear resistance and non-pollution.
The advantage of QPQ
1. High wear resistance
2. High corrosion resistance
3. High fatigue resistance
4. Little deformation
5. Non-pollution
Process case
Auto valve using 4Cr9Si2 steel, the exhaust valve adopt 5Cr21Mn9Ni4N steel.
4Cr9Si2 valve stem and head hardness is 30~37HRC, valve rear hardness more than 48HRC.
5Cr21Mn9Ni4N exhaust valve stem and head hardness is 34~40HRC, valve rear hardness is 50~60HRC after solution. Can also use 4Cr9Si2 steel as the rear and 5Cr21Mn9Ni4N steel welding. The rear after high frequency quenching hardness can reach 55 ~ 63 HRC.
First valve achieve the above technical requirements after preheating process, and then start QPQ treatment , so that forming more than 5 microns compound layer on the surface, increase the high temperature condition of corrosion resistance, abrasion resistance and fatigue resistance.
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