4Cr3Mo2NiVNb（HD）Steel- TJC STEEL.

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.