Steel For offshore structures, Standards Comparison

Introduction

The requirements on structural steel plates for offshore structures differ because of the varying fields of application and location. Today, there are four major standards existing, beside of the shipbuilding standards,
which describe the severe requirements on structural steel plates for offshore constructions. The standards prEN 10225, BS 7191 and the material data sheets of NORSOK (Norwegian standard) are primarily applicable in Europe (North Sea).

The API-standard is mainly applied in American and Asian areas. However, the different standards may also be used in other areas. In some parts, the standards correspond to each other. So, the Norsok standard refers to the prEN 10225 which itself is based on the BS 7191. The more the standards approach each other, the easier it will be for the steel fabricator to develop together with the engineering companies improved steel grades in an economic way.

Here you will find a comparison of the steel grade 355 in the delivery conditions normalized (N) and thermo mechanically rolled (TMCP) and also of the steel grades 420, 450 and 460 in the delivery conditions thermo- mechanically rolled and quenched and tempered (Q+T). The comparison is based on the latest revisions of the mentioned standards at the date of this issue. *) Furthermore, you will find all weldability qualifications of Dillinger Hütte for offshore grades and all approvals for ship-building grades.

*) Remark: In order to ease the use of this document the supplementary requirements of the different standards are not listed.

Grade 355 / API 2H and 2W - chemical compositions

Grade 355N - comparison of tensile strength, yield strength and toughness

355 N	355EM / EMZ	S355G2+N	S355G3+N	S355G7+N S355G8+N S355G9+N S355G10+N	API 2H-50	e. g. E 36 / EH 36
Thick. [mm]	Tensile strength Rm [MPa]
≤25	460 – 620	470 – 630	470 – 630	470 – 630	483 – 620	490 – 620
> 25 ≤40	"	"	"	"	"	"
> 40 ≤100	''	-	''	''	''	''
> 100 ≤150	''	-	-	''	''	''
Thick. [mm]	Yield Strength ReH [MPa]
≤16	≥355	≥355	≥355	≥355	≥355*)	≥355
> 16 ≤20	''	≥345	≥345	''	''	''
> 20 ≤25	''	''	''	''	''	''
> 25 ≤40	≥345	-	''	≥345	''	''
> 40 ≤63	≥340	-	-	≥335	''	''
> 63 ≤80	≥325	-	-	≥325	≥325*)	''
> 80 ≤100	≥325	-	-	''	''	''
> 100 ≤120	≥315	-	-	''	''	''
> 120 ≤150	≥305	-	-	≥320	''	''

355 N	355EM / EMZ	S355G2+N	S355G3+N	S355G7+N S355G8+N S355G9+N S355G10+N	API 2H-50	e. g. E 36 / EH 36
	Minimum Impact Energy Av [Joule] - transverse (average/single) - at a test temperature of
	-40^oC	-40^oC	-40^oC	-40^oC	-40^oC	-40^oC
Surface All thickness < 40 mm < 50 mm	50 / 35 - -	50 / 35 - -	50 / 35 - -	50 / 35 - -	- 41/34 -	- - 24/17
Quarter thick. >40 > 50 < 70 > 70 < 150	- - -	- - -	- - -	- - -	41/34 - -	- 27 /19 34 / 24
Mid-thickness All thicknesses > 40 mm	- 50 / 35	- -	- -	- 50 / 35	- -	- -

Grade 355 TMCP – comparison of tensile strength, yield strength and Toughness

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355 N and TMCP – Comparison of yield to tensile strength ratios

420/450/460 - chemical compositions

420 / 450 / 460 TMCP – comparison of tensile strength, yield strength and toughness

420 / 450 / 460 Q+T – comparison of tensile strength, yield strength and toughness

420 / 450 / 460 TMCP and Q+T – comparison of yield to tensile strength ratios

Weldability qualifications of Dillinger Hütte
for different delivery conditions and steel grades *)