4Cr3Mo2NiVNB steel code name is HD steel, is a kind of air-cooled hardening martensitic hot work die steel, is based on Sweden Udholm QRO-80 steel, by the Huazhong University of Science and Technology and other units[TJC STEEL] independently developed new hot work die steel.  

 

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

 

Citical Point  

AC1 =789℃, AC3 =910℃, MS =363℃  

 

Hot Forming

➣ HD Steel Forging Process Specification  

ITEMS	STEEL INGOT	BILLET
HEATING TEM℃	1140～1180	1120～1160
FORGING TEM(BEGINNING)℃	1080～1140	1060～1120
FORGING TEM(END)℃	≥900	≥850
COOLING METHOD[TJC STEEL]	SAND OR PIT SLOW COOLING	SAND OR PIT SLOW COOLING

 

Preliminary Heat Treatment  

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

 

Quenching Specification  

Quenching temperature is 1130±10℃, oil cold.  

➣ The Relationship Between Quenching Temperature And Hardness And Grain Size Of Hd Steel  

QUCHENING TEM/℃	HARDNESSHRC	GRAIN SIZE/CLASS
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

 

➣ HD Stee’s Hardness Levels on Different Tempered Tem:

Tempered Tem/℃	HRC
	HD Steel	3Cr2W8VSteel
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[TJC STEEL]	51.2	50.0
650	47.0	46.0
700	41.0	34.0

 

Mechanical Properties（Comparing with 3Cr2W8V Steel）

 

➣ HD Steel’s Mechanical Property under Different Room Tem:

Heat Treatments	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	—

 

➣ HD Steel’s Mechanical Property under Different Tem:

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

 

Note: The denominator in αk value is hardness value (HRC).  

 

Performance Characteristics:

On the basis of 4Cr3Mo3V steel, the toughness and thermal stability of 4Cr3Mo2NiVNb (HD) steel at room temperature and high temperature were improved by reducing the content of Mo and V and adding[TJC STEEL] the mass fraction of 1%Ni and 0.15%Nb. The hardness of 4Cr3Mo3V steel at 700℃ could still maintain 40HRC.  Under the same conditions of hardness, HD steel has 50% higher fracture toughness than 3Cr2W8V steel, 70% higher tensile strength at 700℃, 1 times higher cold and hot fatigue resistance and 50% higher hot wear resistance, respectively.  

 

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[TJC STEEL] forging die, in the steel tube hot extrusion convex die, the bottom of the copper alloy tube extrusion die and punch needle, hot extrusion convex die and concave die bearing ring, valve end of extrusion die and mold USES,  The service life of 3Cr2W8V steel is significantly improved.