How to weld cast iron correctly and why does the copper wire electrode not work? We answer the question
Cast iron welding is a rather rare phenomenon in the household. But sometimes you have to fix something and the question arises: how to carry out this operation correctly? On the Internet there is a "old-fashioned" way of welding cast iron with a simple electrode wrapped in copper wire. This does not work. Let's explain why.
Copper wire - like a dead poultice
The bulk of electrodes for welding cast iron contains nickel in its composition - about 92%. There are electrodes where the percentage of nickel with iron is about 50/50. There are electrodes for welding cast iron, where the basis is copper (88%), and iron is 10% in it. Ratio 9: 1. And there are also electrodes, where nickel is 66%, and copper is 30%.
When welding with copper electrodes, the metal deposited on cast iron is a copper alloy interspersed with iron-carbon particles. This character of the structure is determined by the fact that copper practically does not dissolve Fe and C. The properties of welds and their workability depend on the ratio of Cu and Fe in the alloy. An alloy composition of 80–90% Cu and 10–20% Fe is considered optimal.
From this it can be understood that a copper wire wound on an ordinary electrode will not give any sense, because its ratio to iron is critically small. Even if you wind a copper wire of the same cross-section (3 mm) on an electrode with a diameter of 3 mm, then, taking into account the winding, the ratio of copper to iron will become approximately 3: 1. This is still not enough, since in a special electrode the ratio of copper to iron is at least 8: 1. And if you wind a thin stranded copper wire around the electrode, it will simply burn out, and not melt.
The copper wire on the electrode will not bring any sense. On YouTube, they show how to cook in this "old-fashioned" way, but do not show the result. And the seams after such electrodes are more like an accumulation of "snot". We can safely predict that the vice repaired in this way will serve exactly until the first use.
How to cook cast iron correctly?
The answer to this question, unfortunately, is simple, and it does not smell of any simplicity and benefit. It is imperative to buy specialized electrodes and use only them. They are expensive, but they are sold in packs of three. Estimated cost - 100 rubles per electrode.
- But even when working with them, there are certain rules that must be followed.
- Sand the seams and make a small chamfer on them for the penetration depth.
- Heat the parts to be welded with a torch to 50–70 ° C.
- Set the current to 100-110 amperes and cook on a long arc. This is necessary to prevent the electrode from sticking.
- After welding, immediately ignite the torch and use it to slowly cool the metal. Do not allow welded cast iron (or cast iron / steel) parts to cool rapidly.
- Next, beat off the slag and the part can be used!
Have you encountered cast iron welding? Write in the comments how this was done.
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