Because of its resistance to heat and corrosion, stainless steel is widely used in forging. 304/304L, 316/316L, and ferritic stainless steels are the most commonly used in forging. Like other alloys, stainless steels can be forged to make certain products; however, they generally aren't as readily workable as carbon or low-alloy steels. In general, stainless steels have a higher melting point than carbon steels and are more resistant to oxidation. This means that you can use higher temperatures when forging stainless steels.
The properties of stainless steels that make them suitable for forging include their high yield strength and tensile strength. Also worth mentioning is their hardness, which ranges from 60 to 75 on the Mohs scale. Finally, stainless steels have good ductility (the ability to deform without breaking) at room temperature. However, if you expose stainless steel to temperatures above 500°F (260°C), its ductility will decrease.
Stainless steels can be forged into any shape but will not retain their formed shape after cooling. Instead, they will return to their original state. For this reason, stainless steel forges cannot be used to make tools that will be subjected to cutting or grinding operations. Rather, they must be broken down into their component parts and then re-welded together or replaced with new material.
Shafts, valve bodies, valve trim, and the food sector all employ 304 Stainless Steel Forging. 316 (L) stainless steel is the second most prevalent stainless steel grade (after 304 stainless steel) and is widely utilized in food and surgical applications. Unlike 304 stainless steel, which can only be forged above a temperature of 500 degrees Celsius (932 degrees Fahrenheit), 316 stainless steel can be forged at lower temperatures as low as 400 degrees Celsius (752 degrees Fahrenheit). However, since martensitic transformation occurs at about 200 degrees Celsius (392 degrees Fahrenheit), you cannot forge this material below that threshold.
The ability to forge stainless steel allows manufacturers to reduce costs by using mass production techniques instead of customizing parts after they are created. Also, by forging stainless steel valves, shafts, and other metal components, manufacturers can improve their strength while maintaining or even reducing their weight.
Stainless steel can be forged more easily than regular steel because its carbon content is less than 1%. The presence of chromium oxide protects it from melting during heating processes. However, stainless steel still requires heat treatment after forging to relieve internal stress and to promote fracture resistance.
There are two main types of stainless steels: corrosion resistant and non-corrosion resistant. Corrosion resistant stainless steels contain at least 13% chromium by weight and can withstand chemical attacks for long periods of time.
Carbon steel, alloy steel, and stainless steel are common forging metals. Metals like aluminum, brass, and copper may also be forged. With minimum waste, the forging process may create components with excellent mechanical qualities. Parts may be light and strong or dense and hard wearing.
Forging involves shaping hot metal into desired forms. The metal is usually heated above its recrystallization temperature while in contact with a die at a location where forming is to take place. As heat dissipates from the metal, it will assume the shape of the die surface below it. Once cooled, the part is removed from the die.
There are two main types of forges: cold-forged and hot-forged. In a cold-forged process, metal parts are formed by pressing or stamping them out of sheets or bars that have been preheated in order to make them pliable. This process is used primarily for making tools. In a hot-forged process, metal parts are shaped over a mold or pattern directly from molten metal. This process is used primarily for manufacturing heavy duty items such as gears, cutters, and dies.
The quality of the part produced depends on how well the metal is controlled during the forging process. If the metal is not controlled properly, it will not retain its intended shape after it has solidified.
Because 304 stainless steel has a higher hot strength than carbon, alloy, and even martensitic stainless steels, forging it and other austenitic stainless steels needs considerably higher forging pressures or more hammer strokes. The metal may be forged completely without the use of a taper, but it is difficult to weld such shapes because they do not have enough material at their ends to provide a stable electrical connection.
Forging 304 stainless steel can cause it to become harder than normal tool steel, so care should be taken not to cut yourself while using these tools. Also, the metal will become more brittle when forged, so handling it carefully is important for no damage will occur to itself or its surroundings.
Because there is less carbon in 304 stainless steel than in other types, it's more likely to burn if exposed to an open flame. However, because of its high nickel and iron content, it also burns with a bright blue color that many people find attractive.
Burning does not affect the quality of the metal, but it can cause skin irritation like other metals can.
If you decide to forge 304 stainless steel objects, make sure you wear protective clothing and equipment.
Materials for Forging
The most common 300-series steel, 304 stainless steel, is respected for its excellent corrosion resistance and is often used in cookware. Heat treatment may harden martensitic stainless steels; how hard they can become depends on their carbon content. The carbon content of 304 stainless steel is about 16%. It can be hardened by heat treating it to a temperature between 1050 and 1150 degrees F (547-621 C), and then rapidly cooling it down. The hardness of the metal after heat treatment depends on how long it was heated to these temperatures. If the heating and cooling process is done quickly, the metal will remain hard. If not, it will slowly cool back down to room temperature and retain the heat-treated property.
Heating stainless steel does not damage it. In fact, heating stainless steel can help preserve it by giving it more strength without losing its other qualities. For example, if you were to bake regular aluminum pans in a 450 degree F (232 C) oven for an hour, they would lose their shape and be very brittle. But if you heated those same pans in the same oven at 250 degrees F (121 C), they would be much stronger because the heat has a similar effect on both metals. Of course, you should never leave anything in the oven for longer than an hour or so.