What are the types of Manufacturing Process for Seamless Pipes and Welded Pipes?

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Steel pipes that are generally long and hollow in its form undergo a variety of manufacturing processes to ensure their high-functioning usability across industrial and commercial sectors. Steel pipes start off first as raw steels that are cast into hot billets or flat strips. They are then manufactured carefully into either seamless pipes or welded pipes— based on their manufacturing techniques. 

Let’s take a closer look at the different manufacturing processes involved for each category of pipes.

 

Manufacturing Processes for Seamless Pipes

The Mandrel Mill Process

This process is kickstarted by using a solid, rounded steel billet that is put to heat on a very high temperature furnace. Once added into the heated furnace, a hollow is created into the billet. This hollow, known commonly as the mother hollow is drafted through a unique arrangement of a rotary piercer and a set of roller arrangement to ensure the mother hollow created is at the centre of the steel billet. This fast-paced and dynamic rolling process generates the right amount high-tensile strength that helps in producing an accurately pierced hollow pipe— the mandrel mill shell— that is ready to be moved onto next set of roller arrangements and bars called the floating mandrill mill. This arrangement ensures that the outside diameter and thickness gets achieved and the pipe is finished with proportionate sizes all around.  

Upon getting the sizing right, the shell is then re-heated in the furnace for the final process of rolling and firm up the exact sizing and shape. Once done, the pipe undergoes descaling through high-pressure water that eliminates any residuals of iron oxide that tends to be created as part of the process.  

The Mannesmann Plug Mill Process

Much like the Mandrel Mill Process, this process too undergoes a similar treatment using a round billet and the high temperature furnace. However, the major difference between the Mannesmann plug mill process and mandrel is the rolling plug mill which is conical in shape that is lined one above the other – in opposite direction to the material flow. The mill then pushes the billet against the plug to create the hollow shape within. In this method, unlike the previous process, the diameter of the inside of the tube is achieved by a multi-level process. Once it has been creating the pipe undergoes through the reeling and reducing process to even out the thickness of the walls and cut into varying lengths before it goes into reheating, straightening and more. This process is also more likely to be used to make a larger size of seamless pipes. 

Manufacturing Processes for Welded Pipes 

While these are a more financially viable variation, steel can be manufactured through into welded pipes using a handful of methods. Welded pipes, unlike seamless pipes are made from plates, strips or continues coils. Using a plate bending machine or a roller, the steel is rolled in a circular section.  Some types of welding process include:  

Electric Resistance Welding  

In this process, the pipe is manufactured by cold forming a sheet of steel that is flat into a cylinder. With current passing between the two edges of the metal, the heat causes it the ends bond without the need for welding filler material. This process can be undertaken both using high frequency induction and low frequency contact welding depending on the product. For products that require lesser marks and where the process helps reduce the set up in case changing of the pipe size is needed, the high frequency induction process is preferred. However, for welded piped with larger diameter and higher thickness of the wall, the low frequency contact welding is more efficient and preferred.  

Electrical Fusion Welding 

Using coiled steel of similar dimensions, a continuous ribbon of steel is welded together. It then undergoes a heating process that Is then shaped into an oval shape. In the next step, the rolls push the edges of the pipes together, making the welding permanent, The process culminates with the welded pipes being sizes as per the required dimensions. 

While there are various other processes as per of seamless pipes and welded pipes manufacturing processes, these methods find themselves used often within various industries for their agile processing styles. 

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