Cast iron welding paves the way of commercial and residential applications. Once you encounter challenges, this article will help you a lot since we devised a handy guide of facts, steps, and practices to carry out the task smoothly.
Also, this article describes the proper techniques for welding and the tools that can help ensure a smooth weld. It also describes how to tell the difference between cast iron and wrought iron.
A Guide for Cast Iron Welding
Accordingly, wrought iron and cast iron look very similar. In fact, painted black steel and cast iron appear so much alike. Consequently, identifying which material you have remains critical to the success of the piece.
Otherwise, you may choose the wrong application and either damage the piece or have to start over.
The Nature of Cast Iron
Cast iron exists not really as a pure iron but an alloy made of iron and at least two percent or more of carbon. Also, other impurities exist in the mixture. On cast iron blending, this blend of metals melts at a low temperature which makes it ideal to pour into a mold.
When you cast it into any shape, hence coined the term cast iron. In fact, the more intricate the shape, the more likely it becomes cast iron and not wrought iron. This molding process causes the brittleness of cast iron while retaining strength.
Heating iron in a blast furnace acts as the first step to create cast iron welding. Then, the welder casts it, resulting in liquid ore cast into ingots, also known as pig iron.
After cooling, the pigs melted again with scrap metals and carbon. Now, the welder does the casting by shaping the mixture into any shape needed by the manufacturer.
Types of Cast Iron
There transpire various few different types of cast iron welding for your next welding projects:
- Gray – contains graphite and resistant to wear and galling
- Ductile/Nodular – a type of grey cast iron that contains magnesium and cesium with high strength and ductility
- White – includes carbides and resistant to wear
- Malleable – a type of white cast iron with higher ductility
Grey and white cast iron appear as the types most commonly used.
Differences Between Cast and Wrought Iron
There are several essential differences between cast iron and wrought iron. For instance, the type of metal each comprises is very different. Wrought iron is mostly iron with a meager percentage of slag mixed in. This combination of metals is very malleable in comparison to cast iron.
Instead of being poured into a mold, a blacksmith must first heat the wrought iron and then work it by hand, hammering or bending it into shape. Unlike cast iron, wrought iron can be repeatedly heated and bent into shape.
This process makes the metal stronger. Cast iron can only be created once. If it breaks, it must be welded back together if there is any hope of salvaging the piece.
Ductile iron appears as a more modern form of cast iron developed in the 1940s. This metal composite includes magnesium-copper and cerium along with the iron and carbon blend.
When combined, this mixture has a higher tensile strength and greater flexibility. Compared to the older type of cast iron developed and used in the 1700s and 1800s.
Cast Iron Welding Through History
The Chinese came as the first known creators of cast iron welding. Pieces dating to the sixth century B.C. and Chinese pagodas arrived as the first few uses of cast iron. Statues of cast iron have also been found.
Europeans acquired the knowledge at the beginning of the fourteenth century. Yet, America brought the technology in the early 1600s. Additionally, the first American ironwork located at James River in Virginia.
Cast iron comes often used in architectural pieces for decoration. Early attempts created bridges or buildings of cast iron failed due to the brittle nature of the material.
Bridges which used cast iron in their support structures often collapsed. Other bridges used these demolished designs before they collapsed.
In the 1800s, buildings created with cast iron supports and hold heavy machinery. These buildings also thought fireproof capability. When fires erupted, the buildings often collapsed due to the low melting point of the material.
Eventually, cast iron welding directs for aesthetic purposes and mostly found on the facades of buildings to add visual interest.
In the United States, beautiful cast iron porches in New Orleans, Louisiana, and in Richmond, Virginia rose into popularity. Cast iron columns often used for churches and theaters became another point of interest.
How To Do Cast Iron Welding
Since cast iron welding pieces create holistic projects as taught in welding schools. Welding it often means repair to existing sections and not the creation of a new piece. Consequently, most cast iron welding does not involve joint work.
Sometimes parts get damaged at the foundry after creation. Thus, this makes repair necessary, or the hole placed in the wrong area needs fillings. Due to the brittle nature of cast iron, it requires repairs through welding only.
Notably, the cooling speed of cast iron appears important. Stress- and crack-free cast iron is initially created by cooling it very slowly. Therefore, repairs also need slow cooling. Fast cooling cause cracks and increases your workload.
However, repairing the cracks caused by improper technique needs critical focus and welding frequency. 1,450 degrees Fahrenheit maintains critical temperature while welding. The metal cracks once the metal goes beyond this limit.
Steps for Cast Iron Welding and Tips
We recommend slow and uniform preheat to between 500 and 1,200 degrees Fahrenheit. If you go beyond 1,400 degrees Fahrenheit, you risk reaching the critical temperature that will cause the piece to crack.
Preheating means that the piece will then have to be cooled slowly to maintain the weld. Weld the piece with one-inch beads using a low current.
This technique decreases the amount of stress on the section and prevents cracking. Peening done at this point stabilizes the weld.
Choose to weld without preheating when you need to heat the project piece to at least 100 degrees Fahrenheit. But, never make it hotter than a temperature you can safely touch with your bare hand.
Again, experts recommend short welds of approximately one inch, combined with peening.
Allow the piece to cool naturally without the use of fans or water. Now, work safely on another portion of the project while the part that you just completed cools.
Be sure get all the beads going in the same direction. When working in parallel with your new weld, do not make the beads line up.
The End Result
Cracks show up near the weld. These cracks appear normal. But, if the piece appears watertight you have to follow up with a sealing compound. Without a sealer, water intrusion causes rust.
Continue with this process until the project pieces welded back together. Set the piece in the sand to cool overnight if you use the preheat method. Try checking on some welding symbols and their meaning for more info.
Uses of Cast Iron Welding
The most well-known use for cast iron welding exists in cookware. Many people love to cook with cast iron due to its even heating.
A well-seasoned cast iron pan achieves non-stick properties without the harsh chemical sometimes used to achieve that feature in today’s cookware.
Unlike cheaper modern pans, a cast iron skillet lasts forever. Rusted-out cast iron has the capacity for cleaning, re-seasoning, and made suitable for reuse.
Cast iron appears well suited to making beautiful and functional stoves. The appliance molds one piece which eliminates problems associated with welded stoves, such as joint fatigue.
Cast iron welding pipes are loved in the construction industry for their noise-dampening effect and anti-vibration properties. They have high durability and can even prevent fires from spreading through buildings since they are non-combustible, unlike plastic pipes.
Almost all older cars have cast iron engine blocks. Manufacturers of newer cars use aluminum to make their cars lighter. However, a few car companies may be moving back to cast iron because of its greater durability.
You can also find cast iron used for cylinder heads, gear blanks and other parts of the engine.
Cast iron welding appear highly desirable for building materials due to its inherent properties: it resists corrosion, is non-magnetic and has tensile strength. Always prepare your welding helmets and gear-up.
Consequently, you can find cast iron throughout the industry in applications that include sewer and water pipes, manhole covers, columns and bases, railings, lampposts, staircases, and gates.
The wide range of construction types varies from business to residential and commercial. A good welder needs to know how to weld cast iron. The material has high strength, yet brittle and fractures easily.
Due to its extensive use, you probably have lots of opportunities to try your hand at welding cast iron. Though it will take practice to master the process, it is worth your time and material investment to figure it out.