EN9 | 070M55 Medium Carbon Steel BS970 Standard

EN9/070M55 steel,called ’55’ Carbon steel, is a common unalloyed medium steel as per British standard BS 970.It has carbon content with 0.50-0.60% which gives it tensile strength between 500-800Mpa when supplied in untreated condition or normalized condition.EN9 is also suitable in the hardened and tempered condition for tensile ranges of R(700-850Mpa),S(775-925Mpa),and T(850-1000Mpa). For further process,it can be flame or induction hardened to produce a high surface hardness with excellent wear resistance .This material has poor weldability, pre-heat treatment before welding is recommended to prevent cracking.Annealing after welding is also suggested to minimize the risk of breaking.

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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
EN9	0.5-0.6	0.05-0.35	0.5-0.8	≤0.06	≤0.06
070M55	0.5-0.6	0.1-0.4	0.50-0.9	≤0.05	≤0.05

EN9 Series For Speical Applications:EN9K

Grade	C	Si	Mn	P	S
EN9K	0.5-0.6	0.05-0.35	0.5-0.8	≤0.05	≤0.05

3. Equivalent Grade

BS 970-1991:070M55
AISI/ASTM A29:1050,1055
DIN Werkstoff No.: 1.0535,1.1209
BS & DIN European:C50,C55,CK55
JIS G4051: S50C,S55C

4. Mechanical Property

Condition	Normalized	Hardened & Tempered
Condition	N	R	S	T
Ruling Section,inch	4	2	1 1/8	1 1/8
Tensile Strength,Mpa	≥695	≥695	≥775	≥850
Yield Strength,Mpa	≥355	≥465	≥510	≥555
Elongation	≥18%	≥18%	≥18%	≥15%
Hardness,HBW	201-255	201-255	223-277	248-302

EN9 Round steel Lab Tesing Data with Normalizing condition

Diameter,mm	Tensile Strength MPa	Yield Strength MPa	Elongation %	Hardness,HB
Φ360	780	405	20	139-172
Φ430	765	400	22	184-203
Φ510	755	400	23	193-240
Φ600	740	410	22	184-232

5.Forging EN9/070M55 steel

Recommended Forging temperature:800℃- 1200℃,and final forging temperature should not below 800℃,EN9 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 temperaure 810-840ºC with several steps,keep proper holding time depend on the steel size, then followed by cooling in still air.