NES 791 Part 4 Requirements for Weldable Structural Steels

Ministry of Defence Defence Standard 02-791 (NES 791)

Issue 1 Publication Date 01 April 2000

Incorporating NES 791 Category 2

Issue 2 Publication Date December 1988

Requirements For WeldableStructural Steels

Part 4'BX' Quality Steel-Plates

DStan

DStan is now the publishing authority for all Maritime Standards (formerly NESs). Any reference to any other publishing authority throughout this standard should be ignored. Any queries regarding this or any other Defence Standard should be referred to the DStan Helpdesk as detailed at the back of this document.

AMENDMENT RECORD

Amd No Date Text Affected Signature and Date

REVISION NOTE

This standard is raised to Issue 1 to update its content.

HISTORICAL RECORD

This standard supersedes the following:

Naval Engineering Standard (NES) 791 Part 4 Issue 2 dated December 1988.

Ministry of Defence

Naval Engineering Standard

NES 791 Part 4 Issue 2 (Reformatted) December 1988

REQUIREMENTS FOR WELDABLESTRUCTURAL STEELS

PART 4

‘BX’ QUALITY STEEL—PLATES

This NES Supersedes

NES 791 PART 4 ISSUE 1

Record of Amendments

AMDT INSERTED BY DATE

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2

3

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5

6

7

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i

NAVAL ENGINEERING STANDARD 791

REQUIREMENTS FOR WELDABLE STRUCTURAL STEELS

PART 4

ISSUE 2 (REFORMATTED)

‘BX’ QUALITY STEEL—PLATE

The issue and use of this Standard

is authorized for use in MOD contracts

by MOD(PE) Sea Systems and

the Naval Support Command

ECROWN COPYRIGHT

Published by:

Director of Naval ArchitectureProcurement Executive, Ministry of DefenceSea Systems, Foxhill, Bath BA1 5AB

ii

NES 791Part 4

Issue 2 (Reformatted)

iii

SCOPE

1. The requirements for ‘BX’ Quality Steel Plate in thickness above 18mm for special structuralpurposes. Each plate is tested to ensure minimum susceptibility to lamellar tearing.

NES 791Part 4Issue 2 (Reformatted)

iv

NES 791Part 4


v

FOREWORD

Sponsorship

1. ThisNaval Engineering Standard (NES) is sponsored by theProcurement Executive, Ministryof Defence, Chief Naval Architect (CNA), Section NA 132.

2. It is to be applied as required by anyMinistry of Defence contract for steel plate of ‘BX’ qualityfor special structural purposes and is applicable to Surface Ships and Submarines.

3. This NES comprises:

Requirements for Weldable Structural Steels

Part 1 Mild Steel—Plate, Sections and Bars.

Part 2 Notch Tough Mild Steel—Plate.

Part 3 ‘B’ Quality Steel—Plates and Sections.

Part 4 ‘BX’ Quality Steel—Plate.

4. If it is found to be technically unsuitable for any particular requirement the Sponsor is to beinformed in writing of the circumstances with a copy to CNA, Section NA 145.

5. Any user of this NES either within MOD or in outside industry may propose an amendmentto it. Proposals for amendments which are:

a. not directly applicable to a particular contract are to be made to the Sponsor of theNES;

b. directly applicable to a particular contract are to be dealt with using existing proceduresor as specified in the contract.

6. No alteration is to be made to this NES except by the issue of a formal amendment.

7. Unless otherwise stated, reference in this NES to approval, approved, authorized and similarterms means by the Ministry of Defence.

8. Any significant amendments that may be made to this NES at a later date will be indicatedby a vertical sideline. Deletions will be indicated by 000 appearing at the end of the lineintervals.

9. This NES has been reissued to update preliminary pages and because of the changes requireddue to the revision of BS 4360.

Conditions of Release

General

10. This Naval Engineering Standard (NES) has been prepared for the use of the Crown and ofits contractors in the execution of contracts for the Crown. The Crown hereby excludes allliability (other than liability for death or personal injury) whatsoever and howsoever arising(including but without limitation, negligence on the part of the Crown, its servants or agents)for any loss or damage however caused where the NES is used for any other purpose.

11. This document is Crown Copyright and the information herein may be subject to Crown orthird party rights. It is not to be released, reproduced or published without written permissionof the MOD.

12. The Crown reserves the right to amend or modify the contents of this NES without consultingor informing any holder.


vi

MOD Tender or Contract Process

13. ThisNES is the property of the Crown and unless otherwise authorized in writing by theMODmust be returned on completion of the contract, or submission of the tender, in connectionwith which it is issued.

14. When this NES is used in connection with aMOD tender or contract, the user is to ensure thathe is in possession of the appropriate version of each document, including related documents,relevant to each particular tender or contract. Enquiries in this connection may be made ofthe local MOD(PE) Quality Assurance Representative or the Authority named in the tenderor contract.

15. When NES are incorporated into MOD contracts, users are responsible for their correctapplication and for complying with contracts and any other statutory requirements.Compliance with an NES does not of itself confer immunity from legal obligations.

Related Documents

16. In the tender and procurement processes the related documents listed in each section andAnnex A can be obtained as follows:

a. British Standards British Standards Institution,389 Chiswick High Road,London W4 4AL

b. Defence Standards Directorate of Standardization and Safety Policy,Stan 1, Kentigern House, 65 Brown Street,Glasgow G2 8EX

c. Naval Engineering Standards CSE3a, CSE Llangennech, Llanelli,Dyfed SA14 8YP

d. Other documents Tender or Contract Sponsor to advise.

Note: Tender or Contract Sponsor can advise in cases of difficulty.

17. All applications to Ministry Establishments for related documents are to quote the relevantMOD Invitation to Tender or Contract Number and date, together with the sponsoringDirectorate and the Tender or Contract Sponsor.

18. Prime Contractors are responsible for supplying their subcontractors with relevantdocumentation, including specifications, standards and drawings.

Health and Safety

Warning

19. ThisNESmay call for the use of processes, substances and/or procedures thatmay be injuriousto health if adequate precautions are not taken. It refers only to technical suitability and inno way absolves either the supplier or the user from statutory obligations relating to healthand safety at any stage of manufacture or use. Where attention is drawn to hazards, thosequoted may not necessarily be exhaustive.

NES 791Part 4


vii

CONTENTSPage No

TITLE PAGE i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SCOPE iii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

FOREWORD v. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Sponsorship v. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Conditions of Release v. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

General v. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .MOD Tender or Contract Process vi. . . . . . . . . . . . . . . . . . . . . . . . . .

Related Documents vi. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Health and Safety vi. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Warning vi. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

CONTENTS vii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 1. MATERIALS AND MANUFACTURE 1.1. . . . . . . . . .1.1 Chemical Composition 1.1. . . . . . . . . . . . . . . . . . . . . . . .

TABLE 1.1 CHEMICAL COMPOSITION 1.1. . . . . .1.2 Weight Rolling Margins 1.1. . . . . . . . . . . . . . . . . . . . . . .1.3 Flatness 1.1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 2. TEST REQUIREMENTS AND MECHANICALPROPERTIES 2.1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .TABLE 2.1 PLATE 2.1. . . . . . . . . . . . . . . . . . . . . . . . . .

2.1 Ultrasonic Examination 2.2. . . . . . . . . . . . . . . . . . . . . . .

SECTION 3. QUALITY OF FINISHED STEEL 3.1. . . . . . . . . . . . . .3.1 Surface Treatment 3.1. . . . . . . . . . . . . . . . . . . . . . . . . . .

SECTION 4. QUALITY ASSURANCE DOCUMENTATION 4.1. . .

SECTION 5. IDENTIFICATION 5.1. . . . . . . . . . . . . . . . . . . . . . . . . . .

ANNEX A. RELATED DOCUMENTS A.1. . . . . . . . . . . . . . . . . . . .

ANNEX B. DEFINITIONS AND ABBREVIATIONS B.1. . . . . . . .

ANNEX C. SURFACE CONDITION OF HOT ROLLEDHEAVY PLATE, MEDIUM PLATE, AND WIDEFLATS/UNIVERSALS. STANDARD FORREFERENCE IN CASES OF DISPUTE C.1. . . . . . . . .

C.1 SCOPE C.1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .C.2 DEFINITION C.1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .C.3 SURFACE ASSESSMENT C.1. . . . . . . . . . . . . . . . . . . .C.3.1 METHOD C.1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .C.3.2 SURFACE DEFECT AREA C.1. . . . . . . . . . . . . . . . . . .C.3.3 DEFECT DEPTHS C.1. . . . . . . . . . . . . . . . . . . . . . . . . . .C.3.4 SIGNIFICANCE OF DEFECTS C.2. . . . . . . . . . . . . . . .

FIGURE C.1 PLATES <12MM C.3. . . . . . . . . . . . . . .FIGURE C.2 PLATES >12MM <20MM C.3. . . . . . .FIGURE C.3 PLATES 20MM TO 50MM C.3. . . . . . . .

ALPHABETICAL INDEX


viii

NES 791Part 4


1.1

1. MATERIALS AND MANUFACTURE

a. The steel is to comply with the requirements of BS 4360 except where statedherein.

b. The steelmaking process is to be in accordance with BS 4360. The steel is to befully killed, and is to have a grain size of 5 or finer determined by theMcQuaid−Ehn method in accordance with BS 4490. Plate is to be normalized.

1.1 Chemical Composition

a. The ladle analysis of the steel is to be as shown in TABLE 1.1:

C Si Mn S P

% max % min % max % min % max % max % max

0.19 0.10 0.35 1.20 1.70 0.025 0.025

TABLE 1.1 CHEMICAL COMPOSITION

b. The carbon equivalent value when calculated in accordance with the formulain option B7 of BS 4360 is not to exceed 0.45. The ladle analysis is to includedetails of all elements in the carbon equivalent value (CEV) formula.

1.2 Weight Rolling Margins

a. The specified weight for plates is the maximum and the rolling margins are tobe wholly under the specified thickness. Option B16 and TABLE 37 of BS 4360apply.

1.3 Flatness

a. Plates are to be flat within the tolerance limits specified in accordance withBS 4360 Table 5.


1.2

NES 791Part 4


2.1

2. TEST REQUIREMENTS AND MECHANICAL PROPERTIES

a. The steel plate is to be subjected to a tensile test from a sample test piece cutin a crosswire direction in accordance withBS 4360Section 3Clause 21. Tensiletest samples are to be in accordance with BS 4360, Section 3 Clause 22 and thetest results are to be in accordance with mechanical properties shown inTABLE 2.1.

Tensile strength Yield Elongationi

Charpy V Notch

Thickness of

Tensile strength Yieldstress min on

gauge length

Charpy V Notchimpact test

Thickness ofplate min max min

gauge lengthof 5.65 So

Temp Energyplate

N/mm2 N/mm2 N/mm2 % °C min avJ

Above 18mm upto and inc 32mm 460 580 295 20 −30 40

Above 32mm upto and inc 75mm 450 560 280 20 −30 40

TABLE 2.1 PLATE

b. Three adjacent Charpy V-Notch specimens are to be taken from each plate. Thelocation, preparation and testing of the samples is to be in accordance withBS 4360 Section 3.

c. Each broken Charpy test piece is to be examined for crystallinity in accordancewith BS 131 Part 5 and the crystallinity is not to be greater than 75%. Forgeneral estimation of this area the visual method described in BS 131 Part 5Clause 4amay beused. For critical cases approaching 75%crystallinity themoredirect methods described in Clauses 4b and 4c are to be used. If the methoddescribed in Clause 4b is used, the crystalline area is to be estimated from themean values of at least three separate measurements of both width and length.

d. Through thickness tensile testing is to be undertaken on each test pieceremoved from the six test blocks cut from each plate as shown in the sketchbelow. Each test piece is to be of 6mm diam (minimum) and the gauge lengthis to be the full plate thickness with friction welded extension pieces as required.

e. All samples tested from each plate are to have an average reduction of area notless than 20%. If one or more samples fall below 15% reduction of area, twofurther samples are to be taken from the same test block and provided no singlesample falls below 15% reduction of area the plate is acceptable.


2.2

2.1 Ultrasonic Examination

a. Each plate is to be ultrasonically tested in accordance with NES 729. Theacceptance standard is to be L2−C2 to the requirements of BS 5996.

NES 791Part 4


3.1

3. QUALITY OF FINISHED STEEL

a. The quality of all finished steel is to be in accordance with BS 4360: Section 1,except that the reference standard at ANNEX C. of this NES is to apply. Thecorrection of minor defects is to be limited such that the thickness is not locallyreduced by more than 4% below the minimum thickness otherwise allowed.Correction of defects by weld repair is not permitted, options B11 and B12 ofBS 4360 apply.

b. In the assessment of ‘fitness for purpose’ any defect of a type which could affectthis purpose in respect of possible stress raisers or sites of local corrosion, egsharp bottomed scars or pits (see Notes 1 and 2 in Clause 3.c.), pitting withoverhanging edges etc, the purchaser is to report the product to themanufacturer for early agreement on repair or replacement.

c. When the foregoing requirements have been met and there are surfaceblemishes such that it is considered unsatisfactory, because the blemishes marthe appearance of the plate or would adversely affect the adhesion of aprotectivepaint system, then Annex C. is to be used as the basis for arbitration betweenthe purchaser and the manufacturer.

Notes:

(1) For the purpose of this NES a sharp bottomed scar or pit is defined as anyscar or pit which is greater than 0.2mm deep and the depth is greater thanthe width.

(2) To assist in the assessment of borderline cases a reference block is to beused as the datum. This block may be in the form of 50mm ¢ 15mm¢ 2mm with machined slots 0.2, 0.3, 0.4, 0.5, 0.6 and 0.7mm wide. Otherforms of approved assessment methods may be used.

3.1 Surface Treatment

a. All plates are to be abrasively blasted in accordance withNES 755 and inspectedin accordance with Clauses 3.a. to 3.c. Immediately after blasting, the steel isto be coated with priming paint in accordance with NES 757.


3.2

NES 791Part 4


4.1

4. QUALITY ASSURANCE DOCUMENTATION

a. Certification is to be provided to the consignee in accordance with BS 4360 andis to include ladle analysis, mechanical properties, with details of any reheat orretest, and results of the non-destructive examination. This certification isrequired even when inspection has taken place. A copy of each certificate is tobe provided to the MOD Quality Assurance Representative.


4.2

NES 791Part 4


5.1

5. IDENTIFICATION

a. All finished steel is to be legibly marked with the following:

(1) Hard Stamped—markings outlined by circling with paint of acontrasting colour:

(a) specification number;

(b) cast number;

(c) test certificate number;

(d) manufacturer’s works code.

These numbers are to be positioned at the top right and left hand cornerseither on the edge of the plate or on the plate within 16mm of the plateedge.

(2) Painted Markings—located near the end of the plates:

(a) contract number;

(b) destination;

(c) dimensions;

(d) customer identification (last 7 digits of NS Cat No).

(3) Colour Coding—on each plate is to be painted with distinctive green,yellow and white colour bands on diagonally opposite corners.


5.2

NES 791Part 4


A.1 ANNEX A.

ANNEX A.

RELATED DOCUMENTS

A.1 Reference is made to:

Referred to in Clause

BS 131 Part 5 Methods for Notched BarTests—Determination ofCrystallinity

2.c.

BS 4232 Surface finish of blast-cleanedsteel for painting

ANNEX C.

BS 4360 Specification for weldablestructural steels

1.a., 1.b., 1.1b., 1.2a.,1.3a., 2.a., 2.b., 3.a.,4.a., ANNEX C.

BS 4490 Methods for the determination ofaustenitic grain size of steel

1.b.

BS 5996 Method of testing and qualitygrading of ferritic steel plate byultrasonic methods

2.1a.

NES 729 Requirements for Non-destructiveExamination Methods

2.1a.

NES 755 Abrasive Blasting of Steel 3.1a.

NES 757 Application and Uses ofPrefabrication (Shop) Primers

3.1a.


A.2ANNEX A.

NES 791Part 4


B.1 ANNEX B.

ANNEX B.

DEFINITIONS AND ABBREVIATIONS

B.1 There are no Definitions and Abbreviations for this NES.


B.2ANNEX B.

NES 791Part 4


C.1 ANNEX C.

ANNEX C.

SURFACE CONDITION OF HOT ROLLED HEAVY PLATE, MEDIUM PLATE, AND WIDEFLATS/UNIVERSALS. STANDARD FOR REFERENCE IN CASES OF DISPUTE

C.1 SCOPE

a. The surface conditions which supplement the quality requirements of BS 4360for hot rolled heavy and medium plate, also hot rolled wide flats/universals inthicknesses up to 50mm; for thickness over 50mm special agreements may bemade. The requirements for the surface condition of these steel products are tobe used as a basis for arbitration between the supplier and the customer wherethe customer or his representative considers plate surface condition to beunsatisfactory.

C.2 DEFINITION

a. This document relates solely to defects within the rolling margin, and isconcerned with those minor defects which arise in processing despite regularmaintenance of equipment and inspection controls, such as scale, pitting,scores, small blisters and light surface laminations (slivers or shell). These arenot readily seen in the scaled condition and are revealed after descaling.

b. Within the terms of this standard a surface defect is a surface blemish or groupof minor blemishes which do not affect fitness for purpose but mar the surfaceappearance of the plate.

C.3 SURFACE ASSESSMENT

C.3.1 METHOD

a. Both surfaces are to be inspected and assessed independently, bearing in mindthat the resulting thickness must be not less than the minimum permissible.The inspection of plates is to be carried out in good lighting conditions(preferably 400 lux) or with the use of a local light source, in a practical mannerby slowly walking the length of the plate.

b. The depths of surface defects are measured with a surface depth gauge.However, with a little experience it is possible to estimate surface defect depthvisually with a sufficient accuracy, having taken the precaution of gauging somesurface defects in the light conditions prevailing.

C.3.2 SURFACE DEFECT AREA

a. The surface defect area is to be regarded as the area which is circumscribed bya line drawn round the limit of the surface defect at a distance of 80mm. If thesurface defects are significant, ie outwith the standard indicated inFIGURE C.1, FIGURE C.2 and FIGURE C.3, then it is this area that is likelyto be affected by grinding and fairing into the surrounding material.

b. The defect area is expressed as a percentage of the total area of that surfacecontaining the defect.

C.3.3 DEFECT DEPTHS

a. In the case of clusters of surface defects, the average depth is to be used fordetermining if rectification is warranted.


C.2ANNEX C.

C.3.4 SIGNIFICANCE OF DEFECTS (FIGURE C.1, FIGURE C.2 AND FIGURE C.3)

a. The maximum permissible depth and area of defect have been related to platethickness, considering three broad thickness ranges for the sake ofpracticability viz: up to and including 12mm; over 12mm to less than 20mm;20mm to 50mm, and are given in FIGURE C.1, FIGURE C.2 and FIGURE C.3.The smallest defect depth considered is 0.15mm, slightly above the maximumsurface roughness amplitude of 0.1mm for blast cleaned surfaces as defined inBS 4232.

b. Defects within the allowable range (Area A) are considered so insignificant thatrectification is not required. Defects outside this area are normally rectified towithin the permissible range. However, rectification need not be carried out ifthe usefulness of the plate is not impaired by the defects present.

NES 791Part 4


C.3 ANNEX C.

FIGURE C.1 PLATES <12MM

FIGURE C.2 PLATES >12MM <20MM

FIGURE C.3 PLATES 20MM TO 50MM


C.4ANNEX C.

NES 791Part 4


INDEXINDEX.1

ALPHABETICAL INDEX

CChemical Composition, 1.1

Colour coding, 5.1

FFlatness, 1.1

GGrain size, 1.1

IIdentification, 5.1

LLamellar tearing, i

MMarking, 5.1

PProperties, 2.1

QQuality, 3.1, 4.1

SSamples, 2.1

Steelmaking process, 1.1

Surface treatment, 3.1

TTests, 2.1

UUltrasonics, 2.1


INDEX INDEX.2

WWeight rolling margins, 1.1

Inside Rear Cover

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When Defence Standards are incorporated into contracts users are responsible for their correctapplication and for complying with contractual and statutory requirements. Compliance witha Defence Standard does not in itself confer immunity from legal obligations.

Revision of Defence Standards

Defence Standards are revised as necessary by up issue or amendment. It is important thatusers of Defence Standards should ascertain that they are in possession of the latest issue oramendment. Information on all Defence Standards is contained in Def Stan 00-00 Standardsfor Defence Part 3 , Index of Standards for Defence Procurement Section 4 ‘Index of DefenceStandards and Defence Specifications’ published annually and supplemented regularly byStandards in Defence News (SID News). Any person who, when making use of a DefenceStandard encounters an inaccuracy or ambiguity is requested to notify the Directorate ofStandardization (DStan) without delay in order that the matter may be investigated andappropriate action taken.