Cast iron is an alloy of carbon and iron, which also contains alloying additives and impurities.
Cast iron parts are widely used not only in industrial and production areas, but also in everyday life. Cast iron products for private use: plumbing elements, fence structures, car parts and much more. The active use of this alloy leads to the need for welding work. The main difficulties in welding cast iron that home craftsmen encounter:
- due to the fluidity of the alloy, it is recommended to carry out welding in the lower spatial position;
- non-compliance with temperature conditions leads to overheating of cast iron, which can cause the formation of pores and stress in welds;
- cast iron in a molten state can release gases , which will negatively affect the quality of the connection;
- Accelerated or uneven heating or cooling can promote cracking .
In order to obtain a high-quality connection of cast iron products at home, it is necessary to take into account these specific characteristics, as well as correctly prepare the working surface, select the correct welding mode and electrode.
Characteristics of cast iron
The material is an iron alloy containing a large amount of carbon.
The substance gives cast iron hardness. Carbon, which is not a metal, is not capable of forming bonds with iron; it is contained in the alloy in the form of graphite inclusions.
The alloy has the following characteristics:
- Porosity of the structure. The voids quickly fill with gases or absorb oil.
- Relatively low melting point (1200-1250 °C). This explains the high fluidity of the alloy when heated.
- Fragility. Cast iron is not recommended for the manufacture of structures subject to high loads.
- Low ductility.
- Resistant to acids and alkalis. At the same time, the material is sensitive to prolonged exposure to moisture.
Toyota Land Cruiser “TANK” › Logbook › We weld cast iron and steel
Instead of a prologue
The unit is not from my eighty. A unit with TLC-62, which a client brought to my work. But, since episode 62, the father of my eighty, I decided to make an entry in my Tank BZ...
So…
The problem was that the brake caliper bolts on the left steering knuckle kept coming loose.
The owner has already become tired of constantly pulling them up, putting “scrambles” and doing other dances with a tambourine.
Don't go to a fortune teller, the thread is broken there. That's how much - we will resolve the issue only after disassembling the unit.
Well, I won’t describe the procedure for disassembling the hub and other things. If anyone needs it, write in the comments, I will then change the text and add photos of the step-by-step analysis and assembly.
In general, the steering knuckle body was removed, washed and on the workbench.
After troubleshooting the holes, we see that on one of the holes the threads have been completely licked off, and on the second, the outer four turns have been preserved.
Repair method
There are actually quite a few options for solving the problem. 1) drill a hole, cut a thread to a larger size. Use a larger diameter bolt. 2) bush and cut a thread in the bushing for the original bolt. 3) use special fittings to restore the thread.
The first option was no longer necessary, because the owner wants to use standard bolts. 100% right.
The tritium option failed due to the fact that in our village there was no M12x1.25 footer. Only from the Internet, or to order in a week...
Therefore, the second option was chosen. Make a steel bushing. I don’t have cast iron, and I suspect that processing cast iron on a lathe is a mess. Therefore the steel bushing. Several nuances follow: - allowances for fit so that the cast iron ear does not split, but also so that it does not turn when cutting the thread - penetration of one end for the purpose of final fixation of the bushing
If the allowances are more or less clear and in practice everything is done without difficulty, then welding cast iron and metal is a problem. Moreover, using the cold welding method...
In general... Five hours on the first day were spent making several bushings and trying to weld the edges. Horseradish. The electrode that was available for cast iron refused to work properly and along the boundary of the materials, a crack treacherously formed. Naturally, this option did not suit me at all.
The second day was spent searching in our village for a special TsCh-4 electrode. Allows the cold welding method to fuse repair beads onto cast iron and weld cast iron with iron. True, it is necessary to observe some nuances. As a result, somehow this electrode was found on sale individually. God exists!
The rest of the day, about two hours, was spent making the plug boss, jigs for drilling into the boss itself, welding it around the perimeter with cast iron, drilling and cutting threads.
The actual result of repairing the first ear:
Having thought through the rest of my brain, estimating the complexity of the process and its payback, I decided. I will repair the second ear with a futorka. Which, whoops, just in case, I ordered on the Internet. Tomorrow, in theory, he will come to TK.
So, I’ll soon add for comparison, the repair process using the Namba three method
