Casting High Quality C12A Valve Manufacturers Association of America March 2012

BRADKEN ENERGY PRODUCTS March 2012 Elaine Thomas, Director of Metallurgy

Bradken Tacoma

ASTM A217 C12A and ASME Code case 2197-7 Chemistry Element

wt%

C

0.08 – 0.12

Mn

0.30 – 0.60

Si

0.20 – 0.50

P

0.020

S

0.010

Mo

0.85 – 1.05

Cr

8.0 – 9.5

Nb

0.060 – 0.10

V

0.18 – 0.25

N

0.030 – 0.070

Al

.02

Ti

.01

Zr

.01 2

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QUALITY SYSTEM MANUAL

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CERTIFICATES

• ASME • ISO 9002:2002 • Det Norske Veritas • Nuclear Industry Assessment Committee (Audit) • American Bureau of Shipbuilding • LLOYDS Registrar • Boeing D6-56202 © 2011

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EMPLOYEE TRAINING Training Manuals for Skilled PositionsPositions • • Training Manuals for Skilled Continuing Education From Professional Society Participation • • Continuing Education From Professional Society Participation

•

American Society for for Testing and Materials – – American Society Testing and Materials Steel Founders Founders Society of America – – Steel Society of America American Foundry Society – – American Foundry Society American Welding Society – – American Welding Society – American Society for Non-destructive Testing – American Society for Non-destructive Testing Continuing Education From National Conferences – Offshore Technical Conference – – Offshore Technical Conference Submarine Industrial Base – – Submarine Industrial Base Conference Marine Machinery Association – – Marine Machinery Association Hydro Vision – – Hydro Vision Power-Gen

• Continuing Education From National Conferences

– Power-Gen

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THE CASTING PROCESS MOLD CLOSING POURING

MOLDING

PATTERN MAKING

CONTRACT REVIEW SHAKEOUT & BLAST

INITIAL HEAT TREATMENT HEAT TREATMENT RISER REMOVAL FOR PROPERTIES

CORE MAKING

ENGINEERING REVIEW

ORDER ENTRY FINAL INSPECTION

SHIPPING

HEAT TREATMENT

ROUGH MACHINE

GRINDING & WELDING

INSPECTION 6

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ENGINEERING REVIEW • Process Simulation (MagmaSoft) • Process Instruction/Documentation (Process Sheet)

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CORE MAKING • Core Ticket • Process Sheet • Sign-Off Sheet

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MOLDING • • •

Mold Ticket Process Sheet Sign-Off Sheet

Molding Customer: CANYON Serial No: TP 4370-1 Gate Type: tile Tile Size: 5,4 Pattern No. 10-3096 Quantity: Test bar: M Qty: 1 Cast in mold: NO Eng. WC Date: 2/7/11 Material: 903 per cstg Test bar comments: Special Id: A743 CA6NM Cheek: Cookie Cores n/a Break Off Cores n/a Cope Sprue Size 5x5 Spacing: standard Facing Sand: si Flask Size Width Length Height Loose Pcs: 22-popoff vents sticks 168 168 48 Chills: n/a Paint popoff vents thoroughly with silver parting. Using 4" tile, risers will interconect with each other, 12" hi into the riser measuring from Eng. Comments: the contact surface and form a loop around the center of the part Drag Flask Size Width Length Height Facing Sand: si Loose Pcs: 2 wood lock pieces 168 168 48 Chills: 16-8x8x8 Eng. Comments: Rigging Qty.

Size

Open Qty. Sleeves Blind Qty. Sleeves

Open Sand

4

Ht.

Qty.

Size

Ht.

Qty.

Size

Ht.

Blind Qty. Sand

Size

Ht.

Size

Ht.

Qty.

Size

Ht.

Qty.

Size

Ht.

Qty.

Size

Ht.

Qty.

Size

Ht.

Qty.

Size

Ht.

18

24

Size

Ht.

Qty.

Size

Ht.

Qty.

Size

Ht.

Qty.

Size

Ht.

Qty.

Size

Ht.

Qty.

Size

Ht.

Guide: Br=brick, BO=break off core, C=cookie core, D=dome, Nd=neck down, sp=stove pipe, TB=test bar, F=Flange

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Qty.

Size

Ht.

Qty.

9

Size

Ht.

MOLD CLOSING

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MELTING • Radioactivity Test on incoming scrap • Chemical Analysis – Traceable to National Standards – Internal Proprietary Chemistry

• Gas Analysis

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C12A is AOD refined

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ASTM A217 C12A and ASME Code case 2197-7 Chemistry Element

wt%

C

0.08 – 0.12

Mn

0.30 – 0.60

Si

0.20 – 0.50

P

0.020

S

0.010

Mo

0.85 – 1.05

Cr

8.0 – 9.5

Nb

0.060 – 0.10

V

0.18 – 0.25

N

0.030 – 0.070

Al

.02

Ti

.01

Zr

.01 13

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Cross section of an AOD Vessel

Tuyere 14 © 2011 BRADKEN®

Tuyere allows Nitrogen injection

N or Ar

oxygen

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Issues with casting C12A Nitrogen – – keeping N in solution • chemistry • low turbulence gating

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POURING Document Pour Weight, Time, Temperature Sign-Off Sheet Problem Report

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SHAKEOUT AND BLAST • Time to Shake Out • Visual Evaluation after Blast

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HEAT TREATMENT • • • •

Heat Treat Procedures Furnace Uniformity Survey Time & Temperature Fans for cooling Stress prior to Riser removal; Aus/fan Cool + Temper (1350< T < 1450F); PWHT ASME code being discussed: PWHT would be Aus/fan Cool + Temper (1350< T < 1450F);

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Microstructure

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INSPECTION •Personnel • ASNT qualified inspectors Level III on staff Procedure and Acceptance Standards • ASME, ASTM, Internal Quality Procedures Visual Dimensional Magnetic Particle / Liquid Penetrant Ultrasonic Radiography 21 © 2011 BRADKEN®

INSPECTION Which should you choose? • • • • •

Visual Dimensional Magnetic Particle / Liquid Penetrant Ultrasonic Radiography Choices:  critical areas like areas to be welded,  high stress  fatigue areas  Max feasible volume? what level? (1,2,3,4) 22

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Welding C12A Welding & Hydrogen Pipe must be welded in dry environment. Welding followed by hydrogen diffusion cycle. No evidence (so far) that Castings have the same issues as pipe. Unlike Pipe, Casting receive upgrade welds followed by low temperature PWHT.

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C12A

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Issues with casting C12A

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the intercritical region

• •

Perhaps the most common problem with Grade 91 is post-production exposure to temperatures in

Perhaps the most common problem with Grade 91 is post-production exposure to temperatures in the intercritical region—where the tempered martensite begins to transform back into austenite and below the temperature where phase transformation is complete. This can happen in the field where thermal blankets are used for PWHT. If not used properly (e.g. overlapped blankets), regions can get too hot putting the metal into the intercritical zone. When Grade 91 is heated into this intercritical region, the material partially reaustenitizes, and the resulting structure will have substantially reduced creep-rupture strength In the worst case, this material will have lower creep-rupture strength than that of traditional Grade 22.

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Type IV Cracking in Modified 9Cr-1Mo Steel Weld Joint

•

Type IV cracking in the heat affected zone (HAZ) of weld joints limits the life of the component. • Creep tests performed on the steel and its joint revealed that the type IV cracking occurs in the inter-critical region of HAZ, which is sandwiched between relatively higher creep resistant constituents of the joint. • The constrained localized deformation leads to the pronounced creep cavitation in the soft intercritical region of HAZ of the weld joint to yield type IV failure. • The creep rupture life reduction due to type IV cracking in the weld joint of the steel was found to depend on the applied stress and test temperature. • Based on the study, the reductions in 105 hours creep rupture strength of the steel weld joint are estimated as 18 %, 30 % and 45 % of base metal strength at 823 K, 873 K and 923 K respectively. ( i.e. 1022F, 1112F, and 1202F)

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ASME New C12A considerations • ASME Section I Code Case 2192 permits the use of A217 C12A and A426 CP91 castings in the construction of boilers. The case has been revised several times to tighten requirements to deal with problems encountered with this grade (in both its cast and wrought product forms).

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ASME New C12A considerations • Volumetric inspection of castings (per S5, RT, or S7, UT, of A703) has been made mandatory, with the choice of the inspection method to be at the discretion of the material manufacturer unless stipulated otherwise in the PO. –

–

ASME Section I, PG-25 applies an 80% casting quality factor to the allowable stresses of pressure containing castings; but permits use of a 100% factor if castings are RT and MT examined. Castings with up to a 4½ in. nominal body thickness require partial RT, while larger castings require 100% RT.

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ASME New C12A considerations • A full normalizing and tempering heat treatment has been made mandatory following the completion of any major repair to the casting. • Type 4 weld failure w.r.t. stress rupture – especially bad in large welds - Piping issues with thermal blankets which caused overheating.

• FC+T eliminates the type 4 issues in the weld HAZ

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ASME New C12A considerations • It is required that compliance with the specified temperature ranges during any heat treatment operation be demonstrated by thermocouples placed directly on the casting or batch of castings and that a record of these operations be provided to the purchaser.

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ASME New C12A considerations • The hardness requirements currently in the two material specifications, SA-217 and SA-426, have been added to the Code Case. • This has been discussed previously in A01.18 and the 185 HB minimum hardness for this grade was accepted by the ASME committees, even though this is lower than the 190 HB minimum hardness required of wrought grade 91. • The required hardness range is the same as that required by A217/A217M-11 paragraph 7.2 for C12A and by Table 3 of A426/A426M for CP91. 33 © 2011 BRADKEN®

ASME New C12A considerations • It has been made mandatory that the location of all weld repairs on a casting be recorded and that for major weld repairs the dimensions of the repair be recorded, and it is required that this information be documented either on the Material Test Report, for repairs made by the material manufacturer, or on the Manufacturer's Data Report, for repairs performed by the Boiler Manufacturer.

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ASME New C12A considerations This requirement is not relevant to material manufacturer, but might be relevant to valve and pump manufacturers.

It has been stipulated that in cases where the requirement to either re-heat treat or replace a portion of the casting that has been heated above 1470°F is waived due to the fact that the allowable stress values used are less than or equal to those used for Grade 9, the use of the waiver must be recorded on the Manufacturer's Data Report.

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ASME New C12A considerations • Some of these proposed changes are unnecessary and impractical. • Not all users want or need these restrictions. • Mapping all weld repairs is impractical. Majors only. • Re-normalizing and tempering a finish machined casting is impossible. – Dimensions will change and/or warp.

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DISCUSSION

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