Q: I have been considerng the purchase of a spray welding kit in order to perform repairs to cast iron heads. The process seems to make sense, but I´m concerned about the temperature required for consistent results. I believe you need to keep actual weld time to short increments then put the head back in the oven to bring the temperature back up before welding again. I keep reading and hearing conflicting recommendations about temperatures. Some say 500 to 600 degrees, other say 700 and some suggest 900 plus. Which is it? Also, will your benchtop oven DHR-34 or something with a temperature range up to 550-600 adequately handle the heating requirements? If these types of ovens can´t handle the heating, what are other people using?
A: The correct welding temperature is between 650 and 900 degrees. It´s very important that you maintain no less than 400 degrees after you reach your welding temp. Keep in mind that would be the mass temperature. In other words, the farthest point away from the welded area must not drop below 400 degrees. Keep in mind that the higher the maintained temperature, the better the overall weld will be.
Also note, on cast iron with press-in studs, the studs will expand and contract at a different rate than the rest of the workpiece. You may experience loose rocker studs. Always check the rocker studs before AND after welding.
Our DHR-34 oven will not reach the correct temperature for welding. The DHR-34 was designed for head straightening or powder coating. There are ovens available that perform other functions. They are used for thermo cleaning and welding. They are designed to achieve the higher temps required for both welding and cleaning.