The two most common processes for the production of stainless steel flanges are precision casting and forging.
Investment casting
Investment casting takes place by pouring a casting of steel (carbon or stainless) in a liquid state inside a mold composed of a disposable material (such as wax could be).
One of the main advantages of this production method is that it allows you to create complex components precisely because it takes place within well-defined shells.
The shells are formed by the injection of special doughs into a mold, then they are then coated and baked in the oven, at this point they are ready to face the last phase of the process which involves the pouring of liquid steel.
The shells are connected in sequence to each other allowing the liquid metal to fill them all and take the desired shape then, with the consequent cooling and breaking of the shell,
we will get the raw flange.
Now that we have the micro-cast blank, it will be necessary to subject it to different types of processing, first of all the solubilization, if during cooling we have not obtained a correct recrystallization of the material, total or partial turning and threading if necessary.
Forging
Forging occurs by plastic deformation of the materials in our case stainless steel.
The material usually in the form of cylindrical bars or foundry ingots is brought to a temperature higher than that of steel recrystallization allowing it to be worked through the use of specific presses, then a hot molding of the product (alloy) takes place.
The main difference from die casting or precision casting is that the material is not brought to the liquid state.
The forging creates the roughs that will later have to be worked to bring (in our case the flanges) to the dimensions dictated by the legislation.
By comparing the two types of processing and the final products we can say that the use of forged flanges is better.
Forging
keeps the structure of the material compact.
Casting
could create inclusions within the material (bubbles), these inclusions could lead to the formation of breakages and therefore leaks if the flange is put under pressure.
Furthermore, being porous, the mechanical processing of the product is not recommended because it could go to meet the cavity, creating a consequent loss.
This difference between micro-cast and forged flanges also determines the price difference which makes micro-castings more convenient in case they do not have to be installed on systems subjected to high pressures.