Quenched and Tempered High Strength Steel for Leg Components of Jack-up Rigs

Bozhong® 690 CR (SE 690 CR) is a 690 MPa (100 ksi) yield strength quenched and tempered steel adapted for jack-up rig legs of offshore drilling platforms. Bozhong® 690 CR is manufactured via the electric furnace with dephosphorisation, ladle refining and vacuum degassing to provide a reproducible, clean and homogenous steel. This material has been specially designed for offshore applications requiring the use of heavy thick plates (up to 250 mm/10”) with demanding mechanical properties requirements. The chemical composition of Bozhong® 690 CR has been carefully adapted and allows the achievement of high impact values (> 50 J at – 60°C) across the thickness while respecting the tensile properties required.

The main application of Bozhong® 690 CR being the manufacturing of racks and chords, particular attention has been paid on forming, oxycutting and welding properties. The very low carbon content of this material allows cutting and welding under classical conditions, increasing in this way the cost efficiency of manufacturing.

Standards
1.DNV : NVF 690 / grade F
2.ASTM : A 514 – A 517
3.ABS : FH 40

Chemical Analysis
Typical values (weight %)

	C	Mn	Si	P	S	Ni	Mo	Cr	Al
Bozhong®690 CR	≤ 0.15	≤ 1.2	0.15/0.45	≤ 0.01	≤ 0.002	≤ 4	≤ 0.7	≤ 0.7	≤ 0.05
DNV	≤ 0.18	≤ 1.70	0.1/0.5	≤ 0.025	≤ 0.02				0.04/0.1
ABS	≤ 0.16	0.9/1.6	0.1/0.5	≤ 0.025	≤ 0.025				0.04/0.1

Mechanical Properties
Typical and guaranteed mechanical properties (thickness ≤ 210 mm)

	YS (1/2 thickness)	UTS (1/4 thickness)	A%	KVT (1/4 thickness)	KVL (1/4 thickness)	KVT (1/2 thickness)
	(MPa)			-60°C (J)		-37°C (J)
Guaranteed	≥ 690	790 / 940	≥ 16	46 / 32 ave./mini.	46 / 32	46 / 32
Typical	770	840	20	65 / 120	80 / 130	50 / 110
DNV / ABS (≤150 mm)	≥ 690	770 / 940	≥ 14	46 / 32	69 / 48	/