What is WRC-1992 Diagram & application of WRC diagram


WRC-1992 Constitute Diagram and its Uses

WRC-1992 diagram solves many of the problems faced with the Schaeffler and DeLong diagrams. WRC Diagram was developed with data measured by the most recent definition of the Ferrite Numbers (FN) scale, it removed the erroneous Mn coefficient from the Ni eq and eliminated the systematic overestimation of FN for highly alloyed weld metals.

 While it covers a much broader range of compositions than does the DeLong diagram, it has a narrower composition range than the Schaeffler diagram, because it extends only over the composition range of the commercial alloys. Independent data from over 200 weld metals have confirmed the improved prediction accuracy of the WRC-1988 diagram over that of its predecessors and adopted by the ASME therefore in BPVC codes.

WRC-1992 Diagram (Figure A.1) predicts ferrite in Ferrite Number (FN). This diagram is the newest of the diagrams mentioned. Studies within the WRC Subcommittee on Welding Stainless Steel and within Commission II of the International Institute of Welding show the closest agreement between measured and predicted ferrite using this diagram. It should be noted that predictions of the WRC-1992 Diagram are independent of silicon and manganese contents because these elements were not found to have statistically significant effects. The WRC 1992 Diagram is preferred for “300” series stainless steel and for duplex stainless steel. It may not be applicable to compositions having greater than 1% Si.

WRC-1992 Diagram

Practical use of WRC-1992 Phase Diagram

WRC-1992 Diagram
WRC-1992 Diagram
WRC-1992 Diagram
WRC-1992 Diagram

Example of Practical Use of WRC Diagram-2

Consider, we want to predict the Ferrite Number for a weld of UNS S32205 Duplex Steel welded with a “matching” E2209 (SFA  A5.4/A5.4M) SMAW electrode for duplex stainless.

Let’s assume a 30% dilution rate (Where 2205  base metal contributes a total of 30% of the weld (15 % + 15 % from both sides of the base metal) and the E2209-XX  electrode adds the other 70%). The composition of the resultant weld metal can be predicted as below.

Step: 1 We should have a complete chemical composition of base metal (Mills / material suppliers Certificate / PMI Spectroscopy report)

Chemical Composition of UNS S32205 as per PMI Spectroscopy

CSiMnPSCrNiMoNbCuCoN
0.0230.371.500.0180.00122.375.723.210.110.140.080.177

Step 2

We should have filler/electrode chemical composition (As per ASME SEC IIC, Weld Pad Method/ Electrode manufacturer’s suppliers test report)

The Chemical compositions of the undiluted weld metal as per the ASME SEC IIC weld pad test method

Elements Nominal Values in (Wt%)CMnSiSPCrNiMoCuN
Commercial
E2209-16
0.0311.080.590.0070.02522.389.153.350.0960.18

Step 3

Calculate the Chromium equivalent and Nickel equivalent for base metal and filler/electrode composition:

Cr eq = Cr + Mo +0.7Cb

Ni eq = Ni + 35C+20N+0.25Cu

Step 4 :Plotting the values of Cr eq & Ni eq on the WRC-1992 diagram

The UNS S32205 composition is represented by point B (Cr equivalent 25.6%; Ni equivalent 10.1%) and the E2209-XX   electrode composition  by point A (Cr equivalent 25.7%; Ni equivalent 13.8%). As shown in given at the last. At the same time below Table lists the estimated composition of weld metal/synthetic base metal. Table 1 Calculates Weld metal composition / Synthetic base metal composition from  given base metal and Filler/electrode composition, considering 30:70 dilution (Base metal: Filler Metal).

Delong Diagram

Based on the Creq & Nieq & Plotting their values on the WRC diagram as shown below, you will notice that any output weld metal from this mixture of A and B will be on the line that joins them. As we have presumed 30 percent dilution, point C will give the resultant predicted FN = 42.7 approximately as shown in below figure.  (Notice the calculated Weld metal composition point C which is near thick orange line (FN=40) & between thin blue line (FN=46).

Delong Diagram
FN 42.7 Prediction from WRC 1992 diagram for weld sample prepared by E2209 –XX electrode.

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