What Is Forged Steel And How Is It Classified?

What Is Forged Steel and what are the different types?

Forged steel is an alloy of iron and carbon. It is manufactured using a series of compression processes under extreme pressures.

Some of the characteristics of forged steel include finer grain structure, less surface porosity, greater ductility, improved failure rate, and higher tensile strength.

Those characteristics are in reference to how such steel fairs against steel manufactured using different processing methods.

Forged steel has a long history, as the forging process started in ancient times. In the historic ages, the forging process was used to produce materials with distinctive characteristics/properties.

China and Persia were locations where the forging process began to advance. In the modern era, hydraulic hammers and machines mean forging techniques can be applied to many metals, including steel.

How to Weld Forged Steel?

When asking the question: “what is forged steel?”, inevitably the question of welding forged steel also arises.

For welding, you can use most types of welder, including:

• MIG Welders
• TIG Welders

It is highly recommended to preheat your forged steel before attempting to weld, often using a larger tiger torch as the heat source.

TIG welding will be more forgiving when welding this particular material as it will allow you to focus the weld heat without having to add any filler metal.

That said, MIG should work fine, just remember that you will get much better results when preheating.

What is Forged Steel?

When it comes to answering the question “What is forged steel?” it’s helpful to consider the process of manufacturing the alloy.

Steel is heated to a high temperature making it ductile and malleable, so it can be molded into shape by applying pressure. When the best processing methods are used, a bar of steel can be permanently shaped without cracking with steel forging.

Steel forging requires a forge oven, forge furnace, or induction heating system to heat the unprocessed metal to a high enough temperature.

Grain refinement and metallurgical recrystallization results from the thermal cycle and deformation process.

There are three different categories (hot, warm, and cold) of forged steel and the material is classified into those categories based on the forging temperature.

Hot, warm, and cold-forged steel have different pros and cons.

What Is Drop Forged Steel?

Drop forging is the procedure of making metal hot enough for forming it by means of a cast called a metal die-cast, in order to yield different kinds of products. This procedure is used by producers of metal parts to create robust parts for a variety of trades.

This method is one of the most popular metalworking systems throughout time, going back thousands of years

Parts can be fashioned from numerous kinds of metal such as aluminum, brass, and several ratings of steel.

The main two sorts of drop forging include: open-die dropped forging and closed-die drop forging.

Open-die dropped forging

This is the forming of hot metal amid a bottom and top die. After each press, a new form is created with the metal, eventually getting to the desired form.

Open-die forging is typically used for large, less complex parts.

Closed-die dropped forging

This type of forging is widespread as it lets producers create tinnier and increasingly complicated parts. These comprise things like seat belt buckles, climbing gear, spanners, and tractor parts for crop collection.

Parts are shaped by heating, hammering, and pressing into the metal casts. The method is typically finished by means of sanding machines and professional tools that create an even finish.

Less intricate sections are often completed with a single stroke, though usually, numerous blows of differing forces are essential to create a part.

The different methods might comprise: edging, blocking, and finish forging to mold the shape to the correct form.

Which manufacturing industries need drop forging?

A great deal of industries necessitates this type of forging for example aerospace and automotive. They all necessitate robust parts to manufacture safe means of transportation.

Note: Before attempting any form of welding, you should ensure to wear the relevant safety gear such as welding helmets, gloves, and boots.

Cold Steel Forging

Cold forging happens at a temperature underneath the recrystallization temperature of a metal, often at or close to room temperature. 

Subsequently, cold forging is frequently conducted at much lower temperatures than hot or warm forging. There is a larger resistance to distortion by the metals in this procedure. 

Consequently, this process characteristically needs intermediate annealing stages in-between the deformation of the workpiece to reduce stress toughening throughout the forging progression. Annealing is a procedure that reinforces a workpiece by heating it and then letting it gradually cool down to eliminate internal stress.

Because the temperature of the cold forging procedure is close to the toughening temperature of the workpiece, scale creation due to reactions with atmospheric gases should not be a problem in this technique. 

Conversely, the piece is not as flexible throughout the deformation procedure as with different methods, so greater press loads are required in order to form it.

Cold Forging Temperature Range

Cold forging methods are recognized to have the best dimensional precision when likened to hotter forging procedures. 

This feature is due to the detail that the workpiece is distorted close to the net shape of the last creation. Cold forgings don’t need to be cooled down after the forging procedure since they are already made near their toughening temperatures. 

Hot and warm forgings can involve size reduction as they set, a phenomenon that is not a matter in cold forging. Though the workpiece remains in a solid-state in cold forging, the straining from resistance amid the workpiece and the equipment used to deform it can create the temperature of the workpiece to reach up to 250°C. 

As a consequence, the cold forging technique is characteristically used with softer metals such as aluminum, copper alloys, and low alloy steels that typically weigh less than 50 pounds. 

Softer metals are easier to form at lower temperatures and need less forging pressure.

Cold Forging Equipment & Material Considerations 

High efficiency is related to cold forging. The working conditions are not only more favorable at room temperature but are energy-efficient. 

This situation likewise produces high-volume product effectiveness. The cold forging procedure, like the others, advances the mechanical features. 

The final product is characteristically sturdier than the initial material. Furthermore, the proportions of the final, cold-forged product are the most precise out of the other forging procedures.

The apparatus used in cold forging is comparable to the other forging methods but dies really should be made of high-resistance materials to decrease wear throughout the forging method. 

Consequently, engineering design is vital in creating appropriate equipment for this procedure. The higher costs related to the equipment are offset by lengthier working life.

Pros

• Superior dexterity and cut control
• Improved part strength
• Material conservation
• Precision accuracy

Cons

• Requires high forming pressures
• Multiple pre-forming steps required
• Low formability
• Annealing steps are often needed during the process

Warm Steel Forging

The hot forging procedure has features alike to both hot and cold forging and it is the newest developed technique of forging. 

This method takes place at a temperature higher than the work-hardening temperature of the piece, but underneath the temperature at which point scale development occurs. The absence of scale lets the tolerances be nearer in the completed product.

Warm Forging Temperature Range

Conditional on the actual properties of the specific item being forged, warm forging temperatures can vary from 650 and 1000°C. 

Portions with designs that are less difficult in assembly can be created at temperatures from 740 to 770°C, lower than the temperature at which a phase alteration happens. 

Nevertheless, parts made at these temperatures must experience a heat treatment procedure after forging to guarantee it upholds its new structure as it cools.

Warm Forging Apparatus & Physical Considerations 

Subsequently, warm forging temperatures are characteristically lower than those used in hot forging, the workpiece is less supple throughout the course of forging and complex forms are harder to manufacture. 

Warm forgings also feature lower acceptances than cold forged parts. The most common metals that are used in warm forging are steel alloys. 

Warm forging makes it easier to distort steel alloys than in cold forging and can have increased tolerances than those made with hot forging.

Essentially, the advantages mentioned, mean warm forged manufacturing parts are used in higher volume manufacturing such as for automotive parts.

The apparatus used for warm forging should be designed and built to attain a suitable tooling lifespan to boost cost savings. 

Any dies should be well looked after during their working lives to make sure they last in working order.

Pros

• Better formability
• No annealing needed
• Higher deformation ratio
• Requires lower forming pressures

Cons

• Tooling is expensive
• Tooling needs to withstand high temperatures and forming pressures

Hot Steel Forging

Pros

• Great formability
• Requires low forming pressures
• Can forge designs of higher volume and weights
• Complex shapes can be forged

Cons

• Decreased accuracy
• Formation of scale

Warm steel forging provides a great combination of the benefits of cold forging and hot forging, so it is a preferred process by many manufacturers.

However, it does have high tooling costs. The forging temperature for the process is 750 – 950 degrees Celsius.

There are many articles and forums online that you can read to gain more insights into the specifics of different steel forging temperatures and pressures.

The characteristics of forged steel – high strength, resistance, ductility, etc. – mean that it has applications in many industries, including oil & gas, automotive, aircraft, ship, agriculture machinery, hand tool, and more. In the oil and gas industry, for example, forged steel is used for pipe fittings.

Meanwhile, in the automotive industry, steel forgings serve as gear wheels and pulleys.

There are indeed plenty of markets for forged components. You can learn more about the history of steel forging and the difference between closed die forging and open die forging online.