The joint between the reinforcement rod legs of the bird and the cast iron body cracked.

Cast iron is a little tricky to weld. Besides the fact that some alloys are not weldable, all cast iron is very weak in tension, which can result in cracking when the weld cools off and shrinks. Normally the best technique is to preheat the entire casting to a temperature of 1200°F Then weld it. Then let it cool slowly. A critical temperature in most cast iron is about 1450 degrees F. When at this temperature, conditions that can lead to cracking occur. While the arc will heat the casting to temperatures above this level, it is important that the casting not be held at this temperature for long periods of time. In the case of this bird I didn’t want to preheat above 250 degrees F, because I was worried that the preheat would damage the paint. I selected a Nickel-Chromium-Molybdenum super alloy aerospace rod called Hastelloy W. It contains 55% Nickel, which can absorb a whole bunch of carbon and iron and still remain ductile. It has a tensile strength of 110 KSI and an elongation of 42%. Below is a table comparing Tensile Strength and elongation for various alloys

1. Tensile Strength Table

Click image for larger version

Name:	1. Tensile Strength Table.jpg
Views:	174
Size:	19.6 KB
ID:	608635

Below are some pictures of the weld and the whole bird.
Sorry, but I didn't take a picture of the original crack.

2. Whole repaired Bird

Click image for larger version

Name:	2. Whole repaired Bird.jpg
Views:	123
Size:	159.7 KB
ID:	608637

3. Weld with leg and body
Click image for larger version

Name:	3. Weld with leg and body .jpg
Views:	123
Size:	46.0 KB
ID:	608638

4. Close up of weld
Click image for larger version

Name:	4. Close up of weld.jpg
Views:	123
Size:	80.1 KB
ID:	608639

-Don

Attached Files