AN UPDATE ON AWS D1.6 STRUCTURAL WELDING

CODE STAINLESS STEEL

AWS Stainless Steel Welding ConferenceMarch 25-26, 2014 Philadelphia, PA

Richard CampbellBechtel

281-630-8517 (Cell)rdcampbe@bechtel.com

Stainless Steel Structures have beenaround for decades

St. Louis Arch (built early 1965) Chrysler Building (built 1930)

How old is it? 1st Edition 1999 2nd Edition 2007 3rd Edition being balloted hopefully to be published late

2014 or 2015 Prior to 1999 Edition, many end users applied AWS D1.1

rules to stainless steel But, they dont work filler metals, preheat, thermal

conductivity are all different for stainless steels Stainless steel structures:

Buildings Supports (legs, supports for pressure vessels) Ladders Platforms

AWS D1.6 Structural Welding Code Stainless Steel

Clause 1 - General Provisions1.1 ScopeThis code covers welding requirements applicable to stainless steel structures and weldments subject to design stressThis code is not intended to be used for pressure vessels or pressure piping.(AWS D1.1 references AWS D1.6 for welding of stainless steels)1.2 Base Metals1.2.1 Carbon 0.5% Cr 10.5% Fe exceeds content of any other single element Combinations of stainless steels with weldable carbon or low

alloy steels

Clause 1 - General Provisions1.2.2 Stainless steels may include any of the following: Austenitic Ferritic Martensitic Precipitation Hardening (austenitic, semi-austenitic, and

martensitic) Duplex1.2.3 Combinations of base metal (references Annex F very good table of suggested filler metals)1.2.4 Many forms (sheet, plate, tubular, castings, etc.)1.2.6 Thicknesses 1/16 in. or 16 gage

Clause 1 - General Provisions1.2.8 Prequalified Base Metals Austenitic stainless steel base metals (in Table 3.2) whose

filler metals (in Table 3.3) normally produce a small amount of ferrite can be used in prequalified WPSs

All other stainless steels or combinations shall be qualified

1.2.9 Unlisted Base Metals Welding of unlisted stainless steels (not listed in Table 3.2)

shall be qualified to Clause 4 Unlisted metals with same chemical composition &

strength as a listed metal may be welded with a prequalified or qualified WPS for the listed metal

2.1 Scope of Clause 2Major revision from 1999 to 2007 Edition to align with D1.1. Fatigue provisions revised Added fillet welds and plug and slot welds to Tables 2.1 & 2.2

and revised provisions Commentary for Clause 2 added

Part A General RequirementsPart B Weld Lengths and AreasPart C Miscellaneous Structural Details Nontubular and Tubular Connections Statically and Cyclically Loaded

Clause 2 Design of Welded Connections

2.3.5 Welding Symbols use (same as AWS A2.4:2007): S for depth of bevel E for weld sizeAWS A2.4:2012 changes this to: D for depth of bevel S for weld sizeNext D1 codes will most likely reference AWS A2.4:2007 (also affects Clause 6 RT weld size) Table 2.1 provides the maximum allowable stresses for joints

based on type and orientation of applied stresses and based on lesser strength of base metal or filler metal

Being revised

Clause 2 Design of Welded Connections

Clause 3 Prequalification of WPSs3.0 Scope Prequalification of WPSs applies only to austenitic

stainless steel base metals and filler metals that form a small amount of ferrite

AWS B2.1 Standard WPSs also prequalified

3.1 Variables Amps, volts, TS, shield gas composition & flow rate,

position, SAW flux trade designation, filler metal class

3.4 Processes SMAW, GMAW, GTAW, FAW, some SAW

3.6 Base Metals per Table 3.2 Classified by strength, alloy, ASTM specification into 5

groups (A through E)

Clause 3 Prequalification of WPSs3.9 Filler Metals per Table 3.3 (revised from 1999 Edition)

For proposed revision, several paragraphs are being moved from Clause 3 Prequalification to Clause 5 Fabrication (e.g. electrode and filler metal requirements)

1999 said Group B also includes all of Group C base metals of Table 3.2

Written similar to ASME Section IX. But, inconsistencies between text, tables, and figures.Only minor revisions from 1999 Edition to 2007 Edition.

Part A WPS General Requirements4.1.1 For qualification of WPSs for 6 processes in Table 4.14.1.2 Previous Qualification Records The acceptability of qualification to other standards is the Engineers responsibility to be exercised based upon the specific structures and service conditions. AWS B2.1 may be used for the qualification of WPSs and personnel. If in conflict, AWS D1.6 takes precedence.

Clause 4 Qualification

4.1.7 CJP Qualification CJP tests qualify all positions of plate and pipe Also qualifies PJP and fillet welds (macroetch tests also

required for PJP and fillet welds)4.1.8 PJP tests qualify fillets also4.1.10 Mechanical Testing Allows testing per AWS B4.0 or D1.6 (if in conflict, D1.6 takes

precedence)4.2 Essential Variables Table 4.1 Some conflicts between text and table

Clause 4 Qualification

4.3.1 CJP Groove Weld Tests per Table 4.2Clause 4 Qualification

4.3.2 PJP Groove Weld Tests per Table 4.2 A sample weld shall be made using a type of groove

design to be used in construction, but need not exceed 1 in. (for macroetch tests)

Clause 4 Qualification4.4 Fillet Weld Tests per Table 4.2(B) Groove & Fillet welds in same table Note c carried over from AWS D1.1 Note e sends to Table 4.3 but that is Performance Qualification

larger (Errata)

Clause 4 Qualification4.6.11 Overlay Requirements For stainless steel overlay of carbon or low alloy steel Bend tests, penetrant exam, chemical analysis Separate essential variable table

Part B Performance Qualification Requirements for Welders and Welding Operators4.7.3 Previous Qualification Records Allows performance qualification to AWS B2.1 (new in 2007)4.7.5 Base Metals Qualify on any base metal in code With Engineers approval, may qualify with D1.1, Group I or II

Clause 4 Qualification4.7.10 Limitations in Tables 4.3 and 4.4 Note b limits thickness for welder qualification to minimum

WPS limits why? Max. to be welded means what? To change to Unlimited

Clause 4 QualificationTable 4.3 (2nd part) Maximum Outside Diameter or Minimum or OD

Qualified? Note f welder limited to minimum WPS limits for thickness?

4.7.12 No tack welder qualifications tack welding must be done by qualified welders or welding operators

Clause 4 Qualification4.8.3 and 4.9.1 Electrode and Shielding Medium What is an approved electrode and shielding medium? Approved in PQR or welder qualification? Is shielding medium the flux for SAW, shielding gas for GTAW? If change shielding gas composition, does that require

requalification?

Clause 4 QualificationProposed Revision for Next Edition Part A General Requirements Part B Welding Procedure Specification Qualification Part C Performance Qualification

Provides qualification requirements Allows qualification to other standards or AWS B2.1

(Engineers responsibility) Added CVN supplementary essential variables Addresses base metals per AWS B2.1 M-Numbers and Table 3.2

Group Numbers and references AWS B2.1-BMG Cleaned up tables and figures

5.2 Preparation of Base Metal Addresses corrosion properties of stainless Addresses importance of cleaning of stainless5.4 Assembly Tolerances & 5.5 Distortion of Members For future editions, need to evaluate concerns with much

higher thermal expansion & lower conductivity of stainless steels compared with carbon steels

5.10 Weld Cleaning Addresses importance of using brushes made of stainless steels

& iron-free abrasive wheels5.16 Postweld Heat Treatment and Recommendations

Clause 5 Fabrication

2007 EditionPart A General RequirementsPart B RT of Groove Welds in Butt JointsPart C UT of Groove Welds Different than D1.1 because of large grains in stainlessPart D Other Examination MethodsPart E Quality of Welds (for austenitic stainless steels) VT, RT, UT, PT for each of: 6.28 Statically Loaded 6.29 Cyclically Loaded 6.7.7 MT of Ferritic and Martensitic and some Precipitation

Hardening

Clause 6 Inspection

Proposed Revision to Parallel AWS D1.1:2010Part A General RequirementsPart B Contractors ResponsibilitiesPart C Acceptance Criteria New VT TablePart D NDT ProceduresPart E RT of Groove WeldsPart F UT of Groove WeldsPart G Other Examination Methods

Clause 6 Inspection

Example of proposed revision from responses to several interpretation requests on 7.7.1.4 Pre-production bending test: Test to approximately 30o, not destruction At temperatures below 50F, preferable to do continuous slow

bending moving to Commentary Torque test doesnt apply just to below 50F Torque test to values in Tables 7.3 or 7.4, not to destruction

Clause 7 Stud Welding

Since pre-production testing is also used to qualify welders, same information is being copied to a new section

Current 2007 Clause 7 Outline7.1 Scope7.2 General Requirements7.3 Mechanical Requirements7.4 Workmanship7.5 Technique7.6 Stud Application Qualification Requirements7.7 Production Control7.8 Fabrication and Verification Inspection RequirementsAnnex D Manufacturers Stud Base Qualification Requirements

Poor organization

Clause 7 Stud Welding

Draft Revised Clause 7 Outline7.1 Scope7.2 General Requirements7.3 Mechanical Requirements of Studs7.4 Manufacturers Stud Base Qualification Requirements

(moved from Annex D)7.5 Stud Welding Procedure Qualification

7.5.1 Prequalified WPSs7.5.2 WPSs Qualified by Testing

7.6 Stud Welder Performance Qualification

Clause 7 Stud Welding

Draft Revised Clause 7 Outline7.7 Production Welding / Fabrication

7.7.1 Pre-Production Testing7.7.2 Technique7.7.3 Production Welding7.7.4 Workmanship7.7.5 Repair of Studs7.7.6 Removal and Repair7.7.7 Fillet Welding Option

7.8 Inspection and TestingC7 Commentary

More logical organization

Clause 7 Stud Welding

Since stainless steels do not rust, there is no clause pertaining to strengthening and repairing existing structures.

However, there are several paragraphs in Clause 5 that address importance of cleanliness of base metal as well as corrosion issues other than rusting.

No Clause 8 on Strengthening & Repairing Existing Structures

Provides recommendations on which filler metals to use for combinations of

Austenitic stainless steels Ferritic stainless steels Martensitic stainless steels Duplex stainless steels Precipitation hardening stainless steels Stainless steels to carbon and low alloy steels

Informative Annex F Suggested Filler Metals for Various Combinations of Stainless

Steels and Other Ferrous Base Metals

Addresses uses of nonprequalified stainless steels Martensitic stainless steels Ferritic stainless steels Austenitic stainless steels which do not produce ferrite

when welded without filler metal Austenitic stainless steels whose strength cannot be

matched by an AWS classification of austenitic stainless steel filler metal which provide a small amount of ferrite

Duplex stainless steels Precipitation hardening stainless steels

Informative Annex I Nonprequalified Stainless Steels Guidelines for WPS

Qualification and Use

Engineer to evaluate strength, hardness, toughness, corrosion resistance

Addresses concerns about: Hot cracking of austenitics with low ferrite Cold cracking of martensitics and need for preheat, low

hydrogen electrodes, postweld heat treatment Embrittlement of ferritics due to grain growth and use

of low heat input High or low ferrite content in duplex and controlling

heat input Special conditions for welding precipitation hardening Concerns with welding stainless to carbon or low alloy

steels

Informative Annex I

Provides recommended etchants for macroetching stainless steels

For PQRs on fillet welds and PJP groove welds Recommended etchants formulas Recommendations for various metals Safety procedures

Informative Annex N Etchant Solutions

2007 Edition only Commentary is on Clause 2 Commentary will be added for other Clauses as appropriate

in upcoming Edition

Commentary