Carbon and stainless steel forgings

Carbon and stainless steel forgings


Carbon steel forgings and stainless steel forgings are classified according to temperature.  Specifically, the temperature present when they were formed is important. There are three classifications of steel forgings.  They are:

  1. Cold Forging: Cold forging steel is a process that occurs at normal or average conditions and heats up to a maximum of one hundred degrees Celsius. This method uses high forming forces and is most commonly known to have low ratings in each of the following: ductility and formability.  The strength, however, will be high. Brass and copper are formed by cold forging. Bronze is too.
  2. Warm Forging: This process uses higher forming temperatures.  The span for warm forging ranges between Seven hundred fifty degrees to nine hundred fifty. Warm forging actually requires forming forces that are higher than hot forging.  They are also lower than the forming forces used in cold forging. There is low surface scaling during this forming process.
  3. Hot Forging: Hot forging comes with the added benefits of formability.  Temperatures used for forming reach 1250ºC. The hot forging process does not require high-forming forces and presents a stable tensile strength, which is desired. This is the usual method for molding steel alloys.

As the forming temperature changes, so does the narrowness of the tolerances.  The narrowest tolerances achievable are due to cold forging.


Drop forging involves striking steel, much like what was done with an anvil.  The process has a hammer dropping onto a metal piece to change its shape so that it matches the die’s shape. Drop forging is responsible for forged LR90 and SR90* elbows. The two types of drop forged steel are open die forging and closed die forging.

Open Die Forging

Open die forging, also known as free forging, is typically used in the creation of large objects.  Usually forged rollers and things like forged cylinders use this process. With such large creations, railway and aircraft producers use pen die forging most of the time.

When the process of open die forging occurs, a piece of metal is hammered or stamped a number of times by multiple dies.  They do not completely enclose the piece. The desired shape is created this way. It requires a certain series of movements made by the dies. Additional machining is usually required to achieve the needed accuracies. Open die forging has a number of benefits.  One is less waste, another is a finer grain structure. Higher strength is an appreciated quality, and so is increased durability. Managers enjoy the lower cost and the chance of a void goes down.

Closed Die Forging

In the process of closed die forging a pre-cut piece of metal is in the desired shape.  It becomes enclosed between two dies that press towards each other. The heated metal piece resides in the lower die.

This method is also called impression forging. Closed die forging is seen more often on small parts, which include forged flanges and forged fittings. Closed die forging is a process commonly used in the petroleum, mining and vehicle industries.

Closed die forging has very high setup costs so it does not work for short runs.  Die production is also very expensive. Closed die forging is also dangerous. Employees stand a chance of being injured. These efforts can be rewarded with a much stronger final product.  The surface also has a better finish. One additional benefit is the need for more machining at the end. The need is either none or very little.


Carbon steel forgings and pipe have one major drawback.  They rust. This is iron oxide forming on the outside of metal because the iron in the steel reacts with surrounding oxygen. This causes corrosion, which is detrimental in every situation because it weakens the steel. If remedial action does not occur, the pipe will eventually fail. Corrosion of carbon steel usually happens when the humidity in the surrounding air is between 70% and 80%.  Naturally, liquid needs to be present so the temperature above freezing leads to rust. A rust inhibitor can be applied to the pipe and helps prevent corrosion of the steel. Common inhibitors include black mill lacquer, varnish, or a fusion bonded epoxy. Bare steel pipe is very rare and not recommended.

Is One Type of Carbon Steel Pipe Better than Others?

Carbon steel pipe should be chosen according to its application and budget for the steel. There are different types of steel so paying attention to specs and grades for carbon steel is important. The variations that separate carbon from other types are important, as different properties make steel unique. Use advice from an engineer to decide what type of steel is best for the project without surpassing the budget.

There are five main groups of stainless steel. They are Austenitic stainless steel, Duplex stainless steel, Ferritic stainless steel, Martensitic stainless steel and Precipitation Hardening stainless steel.

Believe it or not, stainless steel forgings and pipes can rust. The name comes from the resistance that this material has against rust. It resists better than any other steel, becasue stainless steel is essentially a combination of carbon and chromium. The chromium adds two benefits to the steel.  It improves its appearance and helps it resist corrosion. Chromium adds a mirror appearance to the steel. This shine is seen best in kitchen knives found in the kitchen. Stainless steel can oxidize with chromium but not iron. Chromium actually bonds to oxygen better than iron. The result is something called chromium oxide. The oxidation process of stainless steel can create a helpful layer of chromium oxide on the pipe, which should stop the steel from forming oxide.

Where to find Stainless Steel

Stainless steel is often found being used as a construction material or as part of industrial equipment. It is also common to find stainless steel as the primary component in knives and kitchen utensils. Stainless steel has no need for a protective coating and it is easy to clean and sterilize so it is perfect for commercial kitchens, storage tanks, and surgical tools. In addition to industrial or restaurant kitchens, stainless steel forgings and pipe are found in beer breweries, wineries, and processing plants for food and meat.

Architecture used stainless steel because of the shiny look.  It is quite popular in buildings. Some of the most recognizable buildings use stainless steel type 316. In addition to buildings, stainless steel is used in the construction of popular monuments, sculptures of people, and famous bridges.