6Cr4W3Mo2VNb 6Cr4W3Mo2VNb steel is a high toughness cold-working die steel, and its composition close to the high-speed steel (W6Mo5Cr4V2) of the basic ingredients are the type of substrate steel. It has high hardness and high-speed steel high strength, because no excess carbides, it has a higher than high-speed steel toughness and fatigue. Adding an appropriate amount of niobium in steel, you can play the role of grain refinement, and can improve the toughness of the steel and improve process performance. 6Cr4W3Mo2VNb steel can be used to manufacture cold heading and cold extrusion die molds, mold life were significantly improved.
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6Cr4W3Mo2VNb the chemical composition

C	Si	Mn	Cr	Mo	W	V	Nb	P	S
0.60~ 0.70	≤0.40	≤0.40	3.80~ 4.40	1.80~ 2.50	2.50~ 3.50	0.80~ 1.20	0.20~ 0.35	≤0.030	≤0.030

6Cr4W3Mo2VNb heat treatment process
 Annealing: General isothermal annealing, the heating temperature of 860 degrees, heat 3 ~ 4H, 740 degree temperature 5 ~ 6H, hardness 217HBW. If the isothermal extended to 9H, the hardness can be further reduced to 187HBW, help cold extrusion.
 Hardening: normal quenching temperature of 1080 ~ 1160 degrees, cooling the mold shape and the deformation according to the requirements of the oil can be cold, air cooling or oil quenching - quenching levels.
 Tempering: generally take 520 ~ 580 degrees, tempering holding time 1 ~ 2H, tempering the second. Tempering temperature to take maximum toughness; take the lower limit, the intensity is higher.
 6Cr4W3Mo2VNb thermal processing
　　

Project	Heating temperature / ℃	On forging temperature / ℃	Final forging temperature / ℃	Cooling
Ingot Billet	1140~1180 1120~1150	1100~1150 1080~1120	≥900 900~850	Slow cooling (sand pit or cold) Slow cooling (sand pit or cold)