Is It Possible to Weld Black Pipe to Steel?
Yes, black pipe is made from mild carbon steel, which means it can be welded to other carbon steel using standard steel-to-steel welding techniques.
With threaded connections available and a variety of sizes, black pipe and fittings are ideal for creating DIY projects. You can easily find them at hardware stores or even in scrap piles. The unique look of black pipe adds a vintage or industrial aesthetic to any project. But have you ever wondered about the black coating on it?
Let’s take a closer look at black pipe and its welding capabilities.
Welding Black Pipe
You can weld black “iron” pipe because it’s made from mild steel, not actual iron. Since it’s made from carbon steel, black pipe can be welded using any standard welding method, including MIG, flux core, TIG, and stick arc welding.
However, it’s important to note that black-pipe fittings are typically made from malleable black iron, which can be difficult to weld. Welding black iron fittings may cause damage to the fitting if not done properly.
What is Black Steel Pipe?
Despite its dark appearance and heft, black steel pipe is made from mild steel, not cast iron. It’s typically low-grade and not galvanized. Black pipe is popular for applications like natural gas and propane lines, steam lines, and fire sprinkler systems due to its strength and corrosion resistance.
The term “black steel pipe” is more of a generic name than a technical specification. It refers to regular steel pipe as opposed to galvanized steel pipe. The ASTM (American Society for Testing and Materials) A53 standard defines the specifications for carbon steel pipes.
What is the Coating on Black Steel Pipe?
During the manufacturing process, black steel pipe develops a dark iron oxide coating. This coating enhances its corrosion resistance compared to bare steel. To further protect against rust, black-pipe fitting manufacturers may apply additional coatings such as coal tar enamel, lacquer, or oil.
Is it Safe to Weld Black Pipe?
Yes, it is safe to weld black pipe. Since the pipe is not galvanized with zinc, there’s no risk of producing harmful zinc-oxide fumes during welding. As with any welding project, normal safety precautions are sufficient. It’s a good idea to remove any mill scale or other manufacturing coatings (both inside and outside) before welding, as this can help reduce fumes and improve the quality of the weld. Adequate ventilation and the use of a respirator are always recommended for safety.
Is Black Malleable Iron Weldable?
Black pipe fittings made from malleable iron are tough and resistant to wear and shock. Malleable iron is created by heating white cast iron for extended periods, which gives it these beneficial properties. However, if malleable cast iron is heated beyond its critical temperature of approximately 1700°F (925°C), the carbon in the material can recombine with the iron, turning it back into white cast iron.
As a result, black iron fittings are not ideal for welding because the heat involved can alter their structure, making them brittle and prone to cracking. Instead of welding, brazing or braze welding at temperatures below 1700°F is a safer option for joining malleable iron fittings to black steel pipe. Alternatively, you can use forged iron pipe fittings that are specifically designed for welding, such as socket weld fittings.
In summary, while you can easily weld black pipe (made from mild steel), black malleable iron fittings require special attention and are better suited for brazing rather than welding.
