4Cr3Mo2NiVNb is also named HD Steel, which is a kind of air-cooled hardening martensitic body hot die steel, which is a new hot die steel developed by[TJC STEEL] school of Materials, Huazhong University of Science and Technology and other units on the basis of Swedish Udholm QRO-80 steel.

 

01 Chemical Composition（%）

C	0.35～0.45	Cr	2.50～3.00
Si	≤0.35	Mo	1.80～2.20
Mn	≤0.40	Ni	0.80～1.20
P	≤0.030	V	1.00～1.40
S	≤0.030	Nb	0.10～0.25

 

02 Critical Point

Ac1=789℃，Ac3=910℃，Ms=363℃

 

03 Heat Machining

Spciciation for Forged HD Steel

Type	Steel Ingot	Steel Billet
Heating Tem℃	1140～1180	1120～1160
Beginning Tem℃	1080～1140	1060～1120
End Tem℃	≥900	≥850
Cooling Method	Sand or Pit Slow Cooling	Sand or Pit Slow Cooling

 

04 Preliminary Heat Treatment

Isothermal annealing of forged materials: < 500℃ into the furnace with the furnace heating temperature, heating temperature [TJC STEEL]830 ~ 850℃, holding time (H) 1+1min/mm, isothermal temperature 730±10℃, holding time (H) 2+1min/mm, with the furnace cooling to < 500℃ out of the furnace cooling (HB≤250).

 

05 Quenching Specification

Quenching temperature is 1130±10℃ and the oil is cold.

 

Relationship Between Quenching Temperature and Hardness And Grain Size of Hd Steel

Quenching Tem/℃	HRC	Grain size/Grad
1050	50.5	—
1100	53.5	11
1130	53.5	10
1160	56.0	8～9
1180	56.0	7～8
1200	56.5	7～8

 

Hardness Datas for HD Steel under different Tempering Temperatures:

Tempering Tem/℃	HRC
	HD Steel	3Cr2W8V Steel
300	52.5	51.0
400	52.0	51.0
500	52.5	51.4
530	53.5	52.3
560	54.0	51.5
590	53.8	51.8
620	51.2	50.0
650	47.0	46.0
700	41.0	34.0

 

06 Mechanical Property[TJC STEEL]（Comparing with 3Cr2W8V Steel）

Mechanical Property for HD Steel in Room Tem

Types	1130℃Quenching 650℃Tempering		1130℃Quenching 700℃Tempering
	HD	3Cr2W8V	HD	3Cr2W8V
σ0.2/MPa	1633	1463	1165	952
ψ（%）	32.4	41.8	45.7	41.9
αk/(J/cm2)	38.8	—	48.8	—

 

Mechanical Property for HD Steel in HighTem

 

Tem	650℃		700℃
	HD	3Cr2W8V	HD	3Cr2W8V
σ0.2/MPa	536.9	414	405.3	235
ψ（%）	66.1	49.1	69.3	85.4
αk/(J/cm2)	56/54	—	75/40	62/38

 

07 Performance Features

4Cr3Mo2NiVNb (HD) steel is based on 4Cr3Mo3V steel. By reducing the content of Mo and V and adding mass fractions of 1%Ni and 0.15%Nb, the toughness and thermal stability of 4Cr3Mo2NiVNb (HD) steel can[TJC STEEL] be improved at room temperature and high temperature, and the hardness of 40HRC can be maintained at 700℃.Under the same hardness, HD steel has 50% higher fracture toughness than 3Cr2W8V steel, 70% higher tensile strength at 700℃, 1 time higher cold and hot fatigue resistance and 50% higher thermal wear resistance, respectively.

 

08 Applications

HD steel comprehensive performance is good, suitable for making heating temperature about 700 ℃, using strict hot-work mold, such as ferrous and non-ferrous materials of hot extrusion die, such as hot fine forging die, in the steel tube hot extrusion convex die, the bottom of the copper alloy tube extrusion die and [TJC STEEL]punch needle, hot extrusion convex die and concave die bearing ring, valve end of extrusion die and mold USES, the service life than 3 cr2w8v steel has improved significantly.