EN8 | 080M40 Medium Carbon Steel BS970 Standard

EN8/080M40 steel,as ’40’ carbon steel, is a common unalloyed medium carbon steel as per British standard BS 970.It has medium carbon content with 0.36-0.44% which gives it medium tensile strength.EN8 steel is generally supplied in untreated condition or normalized condition,and also suitable in the hardened and tempered condition for tensile ranges of 625-775 Mpa(Q),and 700-850Mpa(R). For further process,it can be flame or induction hardened to produce a good surface hardness(50-55HRC) and moderate wear resistance.With good homogenous metallurgical structures which gives stable machining properties, EN8 material can be easily machined in any condition.

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1.Supply Form & Size & Tolerance

Hot Forged Round bar:Φ80-Φ1000mm

Hot Forged Square bar: Max Thickness:500mm

Flat bar/Blcoks:Thickness :120-800mm ,Width:120-1500mm

Surface Finish	Black-Forged	Black-Rolled	Turned	Grinding	Polished	Peeled	Cold Drawn
Tolerance	(0，+5mm)	(0，+1mm)	(0，+3mm)	Best h9	Best h11	Best H11	Best H11

2.Chemical Composition

Grade	C	Si	Mn	P	S
EN8	0.35-0.45	0.05-0.35	0.60-1.0	≤ 0.06	≤ 0.06
080M40	0.36-0.44	0.1-0.4	0.60-1.0	≤ 0.05	≤ 0.05

EN8 Series For Speical Applications:EN8A,EN8B,EN8C,EN8D,EN8E,EN8K

Grade	C	Si	Mn	P	S
EN 8A	0.33-0.38	0.05-0.35	0.70-0.9	≤0.06	≤0.06
EN 8B	0.35-0.40	0.05-0.35	0.70-0.9	≤0.06	≤0.06
EN 8C	0.38-0.43	0.05-0.35	0.70-0.9	≤0.06	≤0.06
EN 8D	0.40-0.45	0.05-0.35	0.70-0.9	≤0.06	≤0.06
EN 8E	0.35-0.40	0.05-0.35	0.9-1.1	≤0.06	≤0.06
EN 8K	0.35-0.45	0.05-0.35	0.6-1.0	≤0.05	≤0.05

EN8 Series For Free Cutting:EN8M,EN8AM,EN8BM,EN8CM,EN8DM

Grade	C	Si	Mn	P	S
EN 8M	0.35-0.45	≤0.25	1.0-1.3	≤0.06	0.12-0.20
EN 8AM	0.33-0.38	≤0.25	0.9-1.3	≤0.06	0.12-0.20
EN 8BM	0.35-0.40	≤0.25	0.9-1.3	≤0.06	0.12-0.20
EN 8CM	0.38-0.43	≤0.25	0.9-1.3	≤0.06	0.12-0.20
EN 8DM	0.40-0.45	≤0.25	0.9-1.3	≤0.06	0.12-0.20

3.Relevant Standards

USA	EN/DIN	Japan
1040/1045	C40/CK40/C45/CK45/1.0511/1.1186/1.1189	S40C/S45C

4. Mechanical Property

Condition	Normalized		Hardened & Tempered
Condition	N		Q	R
Tensile Strength,Mpa	≥540	≥540	≥620	≥700	≥700
Yield Strength,Mpa	≥ 280	≥540	≥435	≥495	≥495
Elongation	≥20%	≥20%	≥22%	≥20%	≥20%
ISO V Impact,J	≥28	≥20	≥34	≥54	≥34
Hardness,HBW	152-207	152-207	179-229	201-255	201-255

EN8 Round steel Lab Tesing Data with Normalizing condition

Diameter,mm	Tensile Strength MPa	Yield Strength MPa	Elongation %	Hardness,HB
Φ460	675	375	25	179-187
Φ510	620	360	28	135-167
Φ600	615	355	27	124-156

5.Forging EN8/080M40 steel

Forging temperature around 1200℃,but don’t forge below 800℃,EN8 steel should be cooled as slowly as possible in still air(may get fine grain) or in sand after forged.

6.Heat Treatment

Normalizing

Heat the steel to the temperature 830-860ºC ,keep the temperature depend on the steel size, then followed by cooling in still air.

EN8/080M40 Normalizing Diagram

Annealing

Heat EN8 steel slowly to 680-710°C, keep the temperature stable . Cool slowly in the furnace.

Hardening

Hardening of this grade is carried out from an austenitizing temperature of 820-860ºC followed by oil or water quenching.

Tempering

Carbon steel EN8 or 080m40 can be tempered at a heat of between 550°C to 660°C,heating for about 1 hour for every inch of thickness, then cool in oil or water.