Aircraft Steel BS S99/ 5S99D / 5S99G (826M40)

Technical Data Sheet

BS S99, along with S98 is the British aerospace equivalent of 826M40. A 2 1/2% Nickel-Chrome-Moly high carbon steel, it is available in bars and forgings. S98 is generally supplied as bright bar in either the softened condition (5S99D) or hardened and tempered (5S99G).

Chemical Composition Limits
Weight%	C	Si	Mn	P+S max	Cr	Mo	Ni	Other	Al
S99	0.36-0.44	0.10-0.35	0.45-0.70	P 0.025 S 0.020	0.50-0.80	0.45-0.65	2.30-2.80	-	0.015-0.050
Chemically similar British Specifications BS.970 Pt2
Weight%	C	Si	Mn	P+S max	Cr	Mo	Ni	Other
826M40	0.36-0.44	0.10-0.35	0.45-0.70	P 0.040 S 0.050	0.50-0.80	0.45-0.65	2.30-2.80	-
EN26	0.34-0.44	0.10-0.35	0.50-0.70	-	0.50-0.80	0.40-0.70	2.30-2.80	-
Other Chemically similar Specifications
Weight%	C	Si	Mn	P+S max	Cr	Mo	Ni	Other
WS 1.6745 40NiMoCr105	0.37-0.43	0.15-0.35	0.50-0.70	0.035 max	0.60-0.80	0.40-0.60	2.4-2.7	-

Typical Mechanical Properties

Grade	Treatment	Tensile Strength Rm N/mm²	Proof Stress Rp 0.2, N/mm²	Elongation in 5.65 √Cross Sectional Area%	Hardness HB	Ruling Section
3S99D	Solution Annealed	-	-	-	277 max	-
3S99G	Hardened and Tempered	1230-1420	1080	10	363-415	6"

Availability
Alloy S99 is available in Bar . For all stock availability contact Sales.

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Disclaimer
Every effort is made to ensure that technical specifications are accurate. However, technical specifications included herein should be used as a guideline only. All specifications are subject to change without notice.