How To Weld Cast Iron?

Welding cast iron involves repairing castings without combining the casings to other components. The process takes place in the factory where the production of castings occurs.

How 10 Things Will Change The Way You Approach How To Weld Cast Iron

Following a set of procedures ensure sufficiency of the internal strength to withstand the performance of the component and free from cracks. you have to just follow simple 10 steps to weld cast iron.

Step-01: Determination Of The Alloy
Step-02: Grey Cast Iron
Step-03: White Cast Iron
Step-04: Rod Selection & Clean The Casting
Step-05: Preheat and Post Heat
Step-06: Low Heat Input
Step-07: Slow Cooling to Reducing Internal Stress and Crack
Step-08: Choose A Welding Technique
Step-09: Finishing
Step-10: Minimizing Developing Cracks

The Key Steps in Welding Cast Iron

Step-01: Determination of the alloy

The first step of this type of welding the alloy that contains iron. The cast iron consists of an iron-carbon alloy family with a high carbon content that contributes to their hardness, thus making iron more ductile, which is the ability of iron to be drawn into a wire without breaking. There are different types of cast iron alloy available apart from iron-carbon, including grey cast iron and white cast iron.

Step-02: Grey Cast Iron

The grey cast iron is the most common alloy of cast iron with more weldability and can bend easily without breaking. In the production process, the grey iron-carbon advances to flakes of graphite and transforms into either pearlite or ferrite microstructure crystalline. However, welding grey iron requires a lot of keenness since the graphite flakes may enter into the weld pool, causing embrittlement inside the metal weld and create a problem for the welders.

Step-03: White Cast Iron

White-iron alloy is the next option available used in the process of welding. The alloy has a high ability to hold carbon as iron carbide than the alloy of grey cast iron without expediting it out like graphite. During the manufacturing process, the white iron produces hard cementite and brittle crystalline microstructure. Notably, most of the white cast iron does not require weld, which is a significant concern with the alloy.

Step-04: Rod Selection & Cleaning Both Rod and weld metal

There are three types of electrode or welding rod available in the market. These are: 

• 99% Nickel Rod: This welding rod is costly but weld quality is very good.
• 55% Nickel Rod: This is also good but cheap electrode.
• Steel Rod: Cheapest rod for cast iron welding.

Cleaning the alloy is the next step in the process of iron cast welding. The process involves proper preparation of all castings before starting to weld regardless of the kind of cast alloy chosen for welding. Removal of all the surface material is another necessary activity taken to ensure complete cleanliness of the casting in the weld region.

Elimination of paint, grease, oil, and other obstructive components from the weld region is the next activity. The most important thing to ensure here is highly regulated heat application and carefully in the welding area only for a short time to facilitate ease elimination of any gas trapped in the weld region base metal.

Step-05: Preheating and Post-Heating.

Preheating is another crucial carried out during the casting iron welding process. Too much stress put during the welding process can make all the cast iron vulnerable to cracking. Therefore, regulating the heat in the process of welding is the most important action taken to avoid cracks on the cast iron. Preheating methods involve low input heating and slow cooling.

Taking one of these processes is essential since unlike many metals, cast iron is brittle with the deficient ability of deformation through expansion, contraction, or bending. Usually, heal contains deforming effect on metals, and when part of the metal heat faster or cools quickly, it causes stress leading to the occurrence of cracks on the in the cast iron.

Step-06: Low Heat Input for preventing Crack

The cast iron welding with less heat minimizes the overall temperature. The low heat is crucial in preventing the production of visible cracks and making the iron stronger. Therefore welders need to exercise preheating processes to improve the strength of the weld and reduce the possibility of cracks.

Preheating cast iron before the welding process helps in slowing the rate of cooling on the weld and the area that surrounds the weld. Notably, it is crucial to heat a complete casting with a temperature ranging between 500- 1200  degrees F as high temperature over 1400 degrees F can subject the material to a critical range of temperature.

Step-07: Slow Cooling to Reducing Internal Stress and Crack.

Slow cooling is an essential step used in inducing stress after welding processes. The contraction of the weld can emanate from reliable cooling leading to fragility and simply cracked welds.  Low cooling reduces stress caused by hardening and contraction. Notably, all cast iron can undergo cracking in case of stress, and the chances of cracking can reduce by using the preheating approach.

Therefore control cooling is an essential activity carried while welding cast iron. The process involves wrapping the casting using insulating materials to facilitate a slow rate of cooling. Periodic application of heat on the welding cast iron is another way used in slowing down any natural cooling process to ensure perfect cast iron weld and excellent finishing.

Step-08: Choose a Welding Technique

Choosing the welding technique is another crucial step in the process of weld cast iron. Beveling the metal pieces which to be weld. Following the steps discussed prior, the welder has the responsibility to select the best approach for efficient performance. The welding technique should base on the alloy welded and the size of the metal used in the process of welding.

Step-09: Finishing

Having picked the best technique for the cast iron to require to weld, the final step is finishing the weld. In the process of cooling and contraction of a weld, the tensile stress builds up into the metal iron cast. Thermal contraction is a phase that comes about when the metal iron cast seems to develop cracks.

Step-10: Minimizing developing cracks

The cracking starts when the stress reaches a critical point. Therefore, it is imperative to note the best way of reducing the chances of the weld advancing cracks. The welders can minimize the chances of a weld developing crack by applying stress comprehensively when cooling to help in opposing tensile stress.

Welders can employ a peening technique into a weld bead showing high chances of deformation. The method involves using a hammer ball-pen in performing the moderate strikes on the soft weld. Accordingly, the method helps to minimize the chances of a crack advancing in the weld, and the zone most affected by heat.

Conclusion

Casting iron may seem to be a difficult task and requires proper preparedness and care in both welding and cooling procedures. The iron cast is a metal commonly welded to produce a powerful component with high durability. Therefore, welders should follow the necessary procedures to produce perfect results since shortcuts may lead to cracking ultimately.

FAQ’s

What kind of welding rod do you use on cast iron?

The Nickel is the best premium rod considered in casting iron.

Can you weld cast iron with 6011 rods?

Yes, 6011 helps in adding mild steel in the weld and also is a melting base hence allow a natural flow of the cast iron.

Is it better to braze or weld cast iron?  

Yes. For example, braze welding steel can lead to cast iron but welders should be cautious in combining dissimilar metals in the welding process

Can Cast Iron be repaired?

Yes. But the repair of broken cast iron occurs through welding.

How strong is JB Weld on cast iron?

The JB weld contains 3960 PSI tensile strength and set overnight to a hard bond.