18NiCrMo5 Case Hardening Steel | 17NiCrMo6-4

18NiCrMo5 steel is an alloy structural steel containing Ni-Cr-Mo elements according to the UNI 8550 standard, with high strength and plasticity, moderately high hardenability and good machinability.

In fact, among the special case hardening steels, 18NiCrMo5 steel is the most famous and used steel in Italy, widely used in the production of wear-prone parts such as gears, pinions, bushings, camshafts.

18NiCrMo5 steel is generally used in the quenched and tempered condition or carburized and quenched condition.

18NiCrMo5 STEEL CHEMICAL COMPOSITION

Grade	C	Si	Mn	P	S	Cr	Ni	Mo
18NiCrMo5	0.15-0.21	≤0.4	0.6-0.9	≤0.035	≤0.035	0.7-1.0	1.2-1.5	0.15-0.25

18NiCrMo5 STEEL RELATED STANDARD & EQUIVALENT GRADE

Europe/EN:17NiCrMo6-4 | DIN 1.6566

UK/BS:815M17

France:18NCD6

Sweden:SS2523

18NiCrMo5 STEEL FORGING

Initial Forging Temperature：1100-1150℃
Final Forging Temperature：above 900℃
Forging Ratio：above 4:1
Post-Forging Treatment:As a low carbon Cr-Ni-Mo series alloy steel, 18NiCrMo5 is a white point sensitive steel. After forging, dehydrogenation annealing heat treatment should be done immediately.

18NiCrMo5 STEEL HEAT TREATMENT

Critical Temperature for Heat Treatment of 18NiCrMo5

Ac1:730ºC
Ac3:815ºC
Ms:360ºC

Hardness of Different Types of Annealing for 18NiCrMo5

Soft Annealing:≤240HBW
Isothermal Annealing：149-207HBW
Spheroidizing Annealing：≤207HBW

Temperature Selection for Different Types of Heat treatment for 18NiCrMo5

Normalizing: 850 – 900°C,Cooling in air
Isothermal annealing:850 – 900°C,Cooling to 650°C with 2 hours time holding.Cooling in furnace
Subcritical Annealing:650 – 700°C,Cooling in furnace
Carburizing:870-900°C
Core-hardening:840-870°C,oil-polymer salt bath
Case-hardening:800-830°C,oil-polymer salt bath
Tempering:150-200°C

18NiCrMo5 Steel Mechanical Property with Quenched and Tempered Condition

Thickness/Diameter,mm	Tensile Strength Mpa	Yield Strength Mpa	Elongation %	Impact,KCU, J
≤11	1225-1520	≥980	≥8	≥30
11-25	1030-1325	≥785	≥9	≥32.5
25-40	930-1230	≥735	≥9	≥32.5
40-100	785-1080	≥590	≥10	≥35

Jominy Quenching Test Curve For 18NiCrMo5 Steel

Quenching at 850°C

Distance from quenched end mm		1.5	3	5	7	9	11	13	15	20	25	30	35	40	45	50
18NiCrMo5	HRC Min	39	38	36	34	31	29	27	25.5	23	21	20.5	20	–	–	–
18NiCrMo5	HRC Max	49	48.5	48	46.5	45	43.5	41	40	37	35.5	34.5	33.5	33	32.5	32