About to in-house cast iron welding? Then you need to read the guidelines for welding cast iron to save money and time. Welding failure can be indicated through the damages and cracking. For successful results regarding the critical parts, seeking well-experienced workmanship is wise. You can ensure an effective in-house outcome via four key steps before getting started.
Welding Cast Iron Steps
Identify The Alloy
Cast iron is an essential member of the iron-carbon alloy family. It has a carbon content of 2-4 % and offers hardness characteristics. It is less malleable, and the cooling and heating cycles cause contraction and expansion during the welding. Also, it doesn’t deform or stretch when stressed or heated. For improving the characteristics, you can make use of Grey cast iron and white cast iron.
In grey cast iron, carbon precipitates in graphite flakes during the manufacturing either in ferrite crystalline or pearlite microstructure. It is weldable and ductile. Whereas, white cast iron has no graphite precipitates. It holds a cementite crystalline, micro-structure. It is brittle and hard, not considered for welding purpose.
Clean The Casting
The iron cast welded prepared adequately after cleaning it thoroughly. A complete cleaning achieved by removal of surface material around the areas of the weld. Surface material might include oil, grease, paint and other materials around the weld zone. Careful application of heat gradually for a specific time-period is recommendable to remove entrapped gases from zones. Depositing weld passes over the metal is the most straightforward technique used for testing. It will become porous if the impurities are present and grinding off takes place until porosity disappears.
Pre-Heat Before Welding Cast Iron
Cast Iron is vulnerable toward cracking in the presence of stress. Hence controlling it becomes more critical. It requires three steps, namely Pre-heating, low heat input and, slow cooling. Avoidance of thermal expansion is the prime reason for heating. It is very well-known that when metals get red-hot, it expands. When the entire metal piece is warmed, and expansion takes place with the same rate, no stress arises.
Thermal gradient decreases during the pre-heating, thus minimizing tensile stress during the welding. Selection of low-temperature and a
Welding techniques like stick welding, oxy acetylene welding, and Braze welding are used on cast iron.
Compressive stress opposite to tensile stresses minimize cracking during the cooling process. You can use peening to deform weld bead. The Cooling control is the final and the last steps. In this process, the use of insulating material slow cooling and slow down of periodic heating.
Completion of welding cast iron takes placed with careful preparation. Follow the four steps mentioned in the guideline with appropriate weld techniques.