7 Fabrication Requirements
7.1 Typical Specification Requirements
In addition to special requirements on the materials, special fabrication requirements are also needed to ensure proper corrosion and environmental cracking resistance. These restrictions are applied in addition to the applicable Code requirements. The goal of these additional restrictions is to ensure that the fabrication procedures will not significantly diminish the most important engineering properties, namely the corrosion resistance and the mechanical strength/toughness of the steel. Annex B and Annex C show examples of specifications. Typical user specifications add requirements on the following topics:
7.1.1 Welding
a) Cutting and joint preparation restrictions.
b) Welding process restrictions.
c) A list of acceptable filler metals (including over-alloyed and nickel-based filler metals.
d) The maximum and minimum heat input.
e) A maximum interpass temperature.
f) Require GTAW for single-sided welds (with filler metal except for thin gauge material).
g) The backing and shielding gas compositions.
h) Require heat tint removal on process side.
i) Require removal of arc strikes.
7.1.2 Welding Procedure Qualification (WPS/PQR)
a) Added essential variables for each process.
b) Require the following additional testing—listing the test methods, sample number and locations, and criteria:
i) ASTM A923 Test Method B or Test Method C;
ii) microstructure and percent ferrite from point count;
iii) hardness survey;
iv) for 25 % Cr alloys, ASTM A923 Method C corrosion test (with agreed to criteria).
c) Critical repair welds should be qualified with a partial penetration joint detail and consideration of cumulative heat implications.
7.1.4 NDE
a) Require PT of back gouging.
b) Require PT of completed welds.
c) Require % ferrite check, with ferritescope and calibration to AWS A4.2.
d) Code-required NDE.
Example of Special Welding Procedure Qualification Requirements for DSS
B.1 The WPS/PQRs shall be qualified in accordance with ASME Section IX and the requirements of this
specification. Existing WPS/PQRs, or parts of existing WPS/PQRs may be acceptable provided all of the
requirements are satisfied below.
B.2 Each WPS shall contain the information required by ASME Section IX, QW-250, and the following:
a) the specific welding process or combination of processes to be used in production;
b) for filler metal(s), the specific manufacturer(s) and trade name(s) to be used in production;
c) details of tack welding technique (where applicable);
d) electrical characteristics of welding [i.e. current and voltage range and polarity for each size (diameter) of filler metal];
e) heat input range;
f) welding head travel speed;
g) maximum interpass temperature.
B.3 For repair welding, details of technique for removing and verifying removal of defects shall be supplied to
purchaser for approval before any repairs are done.
B.4 Essential variables for procedure qualification shall be in accordance with ASME Section IX, QW-250, including supplementary essential variables for notch toughness, and those listed below. Any changes in the essential variables of an approved WPS shall require re-qualification.
B.4.1 For manual, semi-automatic and machine welding.
a) Thickness: In addition to ASME Section IX requirements given in QW-403.6, the maximum qualified thickness shall not exceed 1.2T.
b) Joint design: A change from single to double side welding or vice versa.
c) Filler metal type: Any change in manufacturer beyond those approved by the purchaser.
d) Filler metal size: Any change in diameter of the filler metal.
e) Shielding gas flow rate: Any change in flow rate beyond –20/+10 %.
f) Backing gas composition: Any change in the gas composition.
g) Electrical characteristics: Any change in type of current, polarity, or pulse range.
h) Interpass temperature: Any increase in the maximum interpass temperature.
i) Heat input: Any change greater than }10 %. Additionally, for single-sided, complete joint penetration welds, the
WPS shall restrict the heat input during welding for the root pass and hot pass layers to the PQR heat input
values used for these specific layers to }10 %.
B.4.2 For machine welding only:
a) joint configuration: any change in joint configuration outside tolerances specified in the procedure;
b) weld orientation: any change in the weld orientation (e.g. vertical to horizontal);
c) filler metal: for SAW, any change in the brand name and type of flux.
B.5 Test Quantities
The minimum number of mechanical test specimens required for a welding procedure qualification test weld shall be
in accordance with ASME Section IX and Table B.1.
B.6 Test Methods
Test procedures and acceptance standards for supplementary welding procedure qualification tests shall be as
follows.
B.6.1 ASTM A923 Tests
B.6.1.1 Charpy impact testing shall be in accordance with ASTM A923 Test Method B, with test results reported. The number of specimens shall be increased in accordance with B.5. Specimens shall be removed from the locations specified by ASME Section IX. Lateral expansion measurements shall be reported for information. Test parameters and criteria shall also be in accordance with A.1.4.(SEE BELOW).
B.6.1.2 Ferric chloride corrosion tests shall be in accordance with ASTM A923 Test Method C with test results reported. The test specimens shall include weld HAZ and base metal. Test parameters and criteria shall also be in accordance with A.1.4.(SEE BELOW)
B.6.1.3 The rapid screening test (ASTM A923 Test Method A) shall not be used to approve procedures.
B.6.2 Ferrite Tests (Modified ASTM E562)
B.6.2.1 For ferrite assessment during procedure qualification tests, metallurgical sections shall be polished and etched to clearly reveal the two-phase austenite/ferrite microstructure. The area being point counted, either parent material, weld metal or HAZ, should be examined and photographed under a microscope at a sufficient
magnification to fill the field of view and to be able to clearly discriminate between the constituent phases. (For parent plate and weld metal, a magnification of approximately X400 is required, and for HAZ, about X700 to X1000 is recommended.)
B.6.2.2 The photographs shall be overlaid with a grid of at least 100 points and the percentage ferrite shall be calculated from the number of points that fall on the ferrite phase and the total number of points used. Automated counting methods using quantitative metallography equipment can also be used.
B.6.2.3 The ferrite content shall be measured on one of the metallurgical sections using the point counting technique at the following locations:
a) in the parent metal, one measurement on each side of the weld at mid thickness (total of two);
b) in the HAZ on each side of the weld, in the region of the root pass (total of two);
c) in the weld metal, three measurements near to the vertical center line of the weld, one in the cap, one in the root,
and one at mid thickness (total of three).
B.6.2.4 Ferrite content limits shall be:
• in the base metal, 30 % to 65 %,
• in the HAZ, 40 % to 65 % and
• in the weld deposit, 25 % to 60 %.
In less severe services, the purchaser may allow up to 70 %.
B.6.2.5 Experience within the refining industry indicates that this is a difficult test (especially on HAZ) and results are often not accurate. Experienced laboratories should be used.
B.6.3 Photo-micrographs and Macro-examination
B.6.3.1 Photo-micrographs at approximately 400X shall be provided to the purchaser for each of the locations where a phase balance assessment is performed.
B.6.3.2 Photo-micrographs shall show a typical austenite/ferrite microstructure.
B.6.3.3 The macro-examination shall provide evidence that the weld is sound and free from cracks and other
defects with full penetration and fusion between weld passes and parent metal.
B.6.4 Hardness Testing
Hardness testing is required on all weld procedure qualification records. Hardness readings shall be taken in Vickers with a 10 kg load for base and weld metal testing and 5 kg load for HAZ testing. At least eight readings at a depth of 2.5 mm below the inside and below the outside surfaces shall be recorded for both base metals, HAZ and welddeposit. Hardness shall not be above 310 HV average, with no reading over 320 HV for standard DSS grades. For other grades, the limit shall be 340 HV average, with no reading over 350 HV.
B.7 Dissimilar Metal Welds
Dissimilar metal welds (i.e. carbon steel to DSS or austenitic SS to DSS) shall require qualification and testing to the requirements of this specification except that the weldment shall not be subjected to ASTM A923 corrosion testing and the non-duplex HAZ need not be subjected to ASTM A923 Charpy testing.
B.8 Third-party Testing
Third-party laboratories used for testing (for both procedure qualifications and production) shall be experienced in themethods used for DSS testing. When requested, the vendor shall submit to the purchaser, the laboratory name and qualifications.
A.1.4 To ensure adequate corrosion resistance, each heat of material of standard
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of subrata das
Sent: Wednesday, August 11, 2010 12:50 AM
To: materials-welding@googlegroups.com
Subject: [MW:6431] RE: 6399] MW: 6397- What type of Heat treatment to be done
Dear Sir
Following are the Inspection requirements from our client side:
(1) Electrode-ASME Sec II C SFA 5.9 ER 2594;
(2) The PQR shall be qualified as per ASME SEC IX & additional test as per API 938-C
(3) Tensile test, bend test, chemical test as per ASME SEC IX
(4) Ferric chloride corrosion test as per ASTM A 923 Method C
(5) Cross section macro examination; ferrite measurement & hardness testing.
(6) Heat input range to be specified in WPS.
(7) All weld location shall be checked for % ferrite measurement.
Regards
Subrata Das
P. K. Tubes & Fittings Pvt. Ltd.
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of pgoswami
Sent: Monday, August 09, 2010 5:01 PM
To: materials-welding@googlegroups.com
Subject: [MW:6399] MW: 6397- What type of Heat treatment to be done
What's the design code and applicable specifications(e.g NACE, API)....
Please provide these details.Duplex S.S can have different testing requirements based on the end services.
Thanks.
Pradip Goswami,P.Eng.
Welding & Metallurgical Engineer/Specialist
Ontario Power Generation Inc.
Email-pgoswami@sympatico.ca,
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of subrata das
Sent: Monday, August 09, 2010 7:06 AM
To: materials-welding@googlegroups.com
Subject: [MW:6397] What type of Heat treatment to be done
Dear All
Can anyone suggest me which type of heat treatment to be carried out on a PQR test coupon. My PQR test coupon is cladded plate Duplex SS UNS S32750 to SA516 Gr.70. Thickness of Duplex SS UNS S32750 is 3 mm and thickness of SA516 Gr.70 is 10 mm. This PQR to be used while welding in two part welded fittings.
Regards
Subrata Das
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The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.
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The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.
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