Weld Metal Dilution

Date 09-10-2013 17:46 Edited 09-16-2013 20:26

Example fo when: when welding dissimilar metals, to know what the weld seam chemical composition will be.
Example of how: for SMAW (shielded metal arc welding, or covered electrode) dilution is taken as 30%. For SAW (submerged arc welding) is taken as 80%. These are usual figures taken for calculations, doesn't mean that they are exact and precise. However, they lead to acceptable results in the majority of cases.

A couple of more percentages:
MIG: 40%
TIG: 40%

Giovanni S. Crisi
Sao Paulo - Brazil

By 803056

Date 09-11-2013 01:15

To add to Giovanni's applications; it is also used to predict F numbers when welding stainless steels, when calculating the chemistry of a surface weld for cladding, overlays, hard facing, etc. are two additional applications.

By rmdrmd15 (**)

Date 09-16-2013 11:25

These approximate percentages, where do they come from? What are they based on?

By G.S.Crisi (****)

Date 09-16-2013 20:37 Edited 09-16-2013 20:44

They are taught at the Course of Welding Engineering organized by Petrobras, the Brazilian State Oil Company, to prepare its Welding Engineers.
The course has one year duration and who attends it must satisfy two conditions: he (she) must have an engineering degree in any specialty (mechanical, chemical, material, civil etc.) and must be a Petrobras employee.
The course is given at the Sao Jose dos Campos refinery, at 90 kilometers from Sao Paulo, and for 11 months the attendees are full time pupils, they have no other thing to do but study, practice and become good Welding Engineers. I'm not one of them, pity.
Giovanni S. Crisi

By Jorge Giraldo (**)

Date 09-11-2013 19:39 Edited 09-11-2013 20:59

When: Is already answered.

Example of "How": As you see in the Fig. B.24L of AWS A3.0, you can obtain a cross section of your weld (or several) for macroetching, wich consist in polish the sections and attack them with a proper reagent (Nital 5 to 10 is usually used in carbon and low alloy steels) to reveal the weld metal and HAZ. Knowing your initial joint, is possible calculate the Dilution of your particular welding conditions (Process, electrical parameters, joint geometry, etc.) according formula in F24L.

On the image you can see an example of macroetch in BOP weld for hardfacing.

Jorge

Attachment: Dilution.png (27k)

By ssbn727 (*****)

Date 09-11-2013 21:46 Edited 09-11-2013 22:02

Hola Jorge!

So what did you measure for A & B? The formula you're referring to is this correct?

Calculation of Base Metal Dilution from Cross-Sectional Area of Weld Bead.

B
% Dilution = _____ X 100
A+B

   (L)

Figure 24 (Continued)---Parts of a Weld - found on page 81 of AWS A3.0 = F24L correct?

I thought so! So what was the percentage of dilution you calculated?

Respectfully,
Henry

By Jorge Giraldo (**)

Date 09-11-2013 22:45 Edited 09-14-2013 23:57

Hello Henry.
I don't know if I understood well your whole idea...
The formula is correct for any calculation of Dilution, where B represents the area of base metal fused and A area of the filler metal added to the weld.

We used two Eutectic-Castolin electrodes 1/8" Diam. with 4 Amps. and the %D was 15-50% (See attached graphic).

Nice day.

Jorge

Attachment: DilutionVsAmperage.png (8k)

By G.S.Crisi (****)

Date 09-11-2013 23:28 Edited 09-12-2013 18:56

4 Amps? Are you sure? Seems too low an amperage for welding.
Giovanni S. Crisi

By Milton Gravitt (***)

Date 09-12-2013 00:46

Giovanni check the attachment that he posted.

M.G

By G.S.Crisi (****)

Date 09-12-2013 18:55 Edited 09-16-2013 20:39

On the graph that he posted, the amperage goes from 100 to 160 A, a more reliable figure.
Giovanni S. Crisi

By Jorge Giraldo (**)

Date 09-13-2013 00:17

Hello Mr. Giovanni.
You were right. I meant four (4) different Amps. to plott the graph.
Jorge