Casting vs. Forging: Understanding the Differences

Definition of Casting

A liquid or molten material, usually metal or plastic, is poured into a mold during casting and allowed to harden into the desired shape. The material used for casting is usually heated until it becomes a liquid or molten state, which is then poured into a mold that has been created to the desired shape of the final product. Once the material has been poured into the mold, it is left to cool and solidify, after which the mold is removed, leaving behind the solidified casting. The casting may require further processing, such as trimming or polishing, to achieve the final desired shape and finish. Casting is commonly used to create complex shapes or parts that would be difficult or impossible to manufacture through other processes. It is used in a wide range of industries, including automotive, aerospace, and construction. Different types of casting methods include sand casting, investment casting, die casting, and continuous casting.

What is Forging?

Forging is a manufacturing process in which a solid piece of metal is shaped into a desired form by applying localized compressive forces. The process typically involves heating the metal to a specific temperature, which makes it easier to shape, and then using a hammer, press, or other forging tool to apply force to the metal and shape it into the desired form. Forging can be used to create parts with high strength, durability, and resistance to fatigue and impact. This makes it a popular method for producing components used in high-stress applications, such as aircraft and automotive parts, industrial machinery, and construction equipment. There are several different types of forging methods, including open-die forging, closed-die forging, and roll forging. Each method has its own unique advantages and disadvantages, and the choice of method depends on factors such as the size and complexity of the part, the desired properties of the final product, and the quantity of parts needed.

What is the Difference Between Casting & Forging?

Casting and forging are two different manufacturing processes used to shape metal. The casting process involves pouring molten metal into a mold and allowing it to solidify into the desired shape, while forging involves using compressive forces to shape a solid piece of metal. In casting, the molten metal is poured into a mold, which can be made of various materials such as metal, sand, or ceramic. The mold is then removed once the metal has solidified, and any finishing work is done on the casting. This process is ideal for creating complex shapes and intricate designs, but the final product may have some surface defects and may not be as strong as a forged part.

In forging, a solid piece of metal is heated to a specific temperature and then shaped using compressive forces, such as hammering or pressing. This process produces strong, durable parts with excellent mechanical properties, making them ideal for high-stress applications. Forged parts also have a higher level of structural integrity and are less likely to have surface defects. Overall, the main difference between casting and forging is the starting material and the method used to shape it. Casting uses molten metal and a mold, while forging uses a solid piece of metal and compressive forces to shape it. The choice of process will depend on the specific application and the desired properties of the final product.

Casting and Forging Process in brief

Casting and forging are two widely used manufacturing processes that involve shaping metal into desired forms.

· The casting process involves pouring molten metal into a mold and allowing it to solidify into the desired shape. There are various types of casting methods, such as sand casting, investment casting, die casting, and continuous casting, depending on the type of material and the complexity of the part being produced. Casting is suitable for creating complex shapes and intricate designs that may not be achievable with other processes. However, the final product may have surface defects and may not be as strong as a forged part.

· Forging, on the other hand, involves heating a solid piece of metal and shaping it using compressive forces such as hammering or pressing. There are several types of forging methods, including open-die forging, closed-die forging, and roll forging, depending on the size and complexity of the part. Forging produces strong and durable parts with excellent mechanical properties, making them ideal for high-stress applications.

In summary, casting and forging are two different processes used to shape metal into desired forms. The choice of process will depend on the type of material, the complexity of the part, and the desired properties of the final product.

Conclusion

At QFCM, we offer a range of cleaning solutions that are specially designed for the casting and forging industries. Our products can help to remove contaminants and impurities from metal parts during the manufacturing process, ensuring that the final product is of the highest quality. Whether you are casting or forging parts for aerospace, automotive, or industrial applications, our team of experts can help you find the right cleaning solution for your needs. By partnering with QFCM, you can be confident that you are using the most effective cleaning solutions available, and that your parts will meet the highest standards of quality and performance.

Different Types of Forging Presses

Mechanical Forging Presses

Mechanical Forging Presses generally incorporate a ram that moves in a vertical direction to exert a squeezing action on the work piece, in contrast with the repeated blow characteristics of hammer forging. In general, presses can produce all of the same types of forgings produced on hammers and, in addition, can forge some alloys of moderate ductility that would shatter under the fast impact of the hammer die.

Driven by a motor and controlled with an air clutch, mechanical presses have a full eccentric type of crankshaft that imparts a constant length stroke to a vertically operating ram. Ram speed is greatest at the center of the stroke, but maximum force is not achieved until near the bottom of the stroke. Because the stroke is a fixed length, care must be taken to ensure that the closure allowed is not so small as to risk having the press “stick” at the bottom of the stroke, and not complete the stroke. Such an event can cause severe damage to the press or, in the least, substantial downtime to “burn” the dies apart to free the press.

Mechanical presses are best suited for low profile forgings and usually incorporate knockout/liftout pins in the dies which automatically eject the forging from the die allowing the die, and thus the forging, to be designed with less draft allowance. This can reduce weight and subsequent machining. Stresses in press dies are usually high, but there is very little impact load so harder die can be used without the risk of breakage that might be experienced on a power hammer.

Tooling costs are generally higher and the tool change and setup time is slower, so presses have been more cost effective on longer forging runs. As technology and systems change rapidly, this may not be true in the future. Higher production rates are possible on some part configurations with presses than with hammers. Many forging presses can deliver up to 70 strokes per minute. In general, presses require less operator skill than forging hammers.

Hydraulic Forging Presses

Hydraulic Forging Presses are not commonly used for conventional hot forging due to the extremely slow ram speed and high die contact time. They are, however, used extensively in open die forge applications and also for very large tonnage applications, primarily to forge materials other than steel. These machines are ideal for isothermal forging applications because of heir slow squeezing operation. The largest of these machines is rated at 50,000 tons with a die area of 12 feet by 32 feet. Generally, a water hydraulic system is used to drive these machines.

Die contact time of the various types of equipment is of interest to the forger, for the longer the contact time, the lower the die life tends to be. This is due to both the loss of heat in the work piece and the possible elevation of the die temperature above its design specifications. The contact times vary for the amount of deformation in particular forging operation. The heavier the deformation, the longer the contact time.

Screw Press

The Screw Press uses a friction, gear, electric, or hydraulic drive to accelerate the flywheel and screw assembly to convert angular kinetic energy into the linear energy available in the ram. In friction drive machines, vertically mounted drive wheels are rotated continuously. To make a downstroke, the drive wheels are shifted to enable one wheel to engage the main flywheel and accelerate the ram down. When the energy is completely used up as the stroke is made, the flywheel, screw, and ram come to a stop.

The drive wheels are then shifted to allow the flywheel to be reversed and return the ram to the top. In direct electric drive machines, a reversible electric motor is built directly onto the screw and frame. This design uses a screw which does not move vertically but is threaded into the ram/nut assembly. As with the friction drive machine, the flywheel must come to a complete stop and all energy used up in order to reverse the ram back to the top. A variation of the direct drive uses a gear drive and slipping clutch flywheel assembly in which the drive gears and screw are protected from overloading by the slipping clutch.

This design is used in larger capacity machines. Both electric and hydraulic drive motors can be used. The largest screw presses in operation (16,000 ton nominal rating) are based on this design. The total energy available in the screw press is determined by how much kinetic energy is input to the flywheel by the drive system. It is possible to control the force of each blow by controlling the speed of the flywheel. This can be accomplished by disengaging the drive from the flywheel at predetermined times to limit flywheel RPM and, thus, ram speed.

New design technology allows not only the force of each blow to be controlled, but also the stroke distance of the ram. The hydraulic clutch drive screw press design used in the machines in our Lebanon facility allows the operator to program individual blow control settings for both stroke and force. This feature means that no more energy than necessary is used to make a part, and also lets preformed “pancake” shapes to be made to consistent thickness. This design also allows the press to be cycled faster than conventional friction or direct drive machines. The flywheel is disengaged from the screw and ram assembly hydraulically, prior to completion of the stroke, and continues to rotate. The ram is then returned to the top position by auxiliary hydraulic cylinders, not by the main drive system. Because the flywheel can then be brought back to speed quickly, the press has its maximum energy and force available very shortly after the downstroke begins.

These features, plus the availability of using knockout/liftout pins to remove forgings from the dies, allows the screw press to take advantage of some of the most desirable traits of both hammers and mechanical presses. These include low die contact time, consistent and repeatable blow force, reduced draft angles to limit waste material, and easier die setting.

Upsetter

Upset forging, sometimes called Heading, is performed on a horizontal forging machine called an Upsetter. It is essentially a process for enlarging and reshaping certain sections of a bar or tube. In its simplest form, hot upset forging is accomplished by holding the heated stock between two half dies and applying pressure to the end of the stock in the direction of its axis with a heading tool, which upsets (spreads) the end by metal displacement.

Present day machines and tooling permit the use of multiple pass tooling that can produce complex shapes accurately and economically. The process is now widely used for producing shaft type parts, ranging in complexity from simple headed bolts to flanged shafts, cluster gears, and wrench sockets that require simultaneous upsetting and piercing. Forgings requiring center (not at the bar end) or offset deformation may also be produced.

Hot upsetting may be used to preform or prepare sock for another forging machine, such as a hammer or press, or as a finishing operation following forging such as upsetting a flange on the end of a crankshaft. In addition to upsetting, the heading tools are used for piercing, trimming, extrusion, and bending. In the upset forging process, the working stock is confined in the die cavities and the heading action creates the pressure required to fill all of the die impressions completely. Since the dies are split, a wide variety of shapes can be forged and easily removed from the tooling, which is primarily composed of three die elements – two gripper and cavity dies (one is stationary and one is fastened to the moving die slide), and the punch, which is fastened to the header slide (ram).

During the upset forging cycle the movable die slides to the stationary die to grip the stock. The punch that is fastened to the header (ram) advances forward and forces the stock into the cavities of the dies. When the punch retracts about 60% of its full stroke. The movable die slides to its open position allowing the forging to be released. The forging may then be shifted down to the next pass (die) where the cycle may be repeated. Many forgings require multiple passes (some as many as six) before completion. The stock may also be forged on one end and then slipped over (reversed) to be forged on the other end in one heat-cycle. After completion of the forging operation, the forgings are usually dropped through the throat of the machine to a conveyor that delivers the hot forgings into a metal tote box for cooling and transportation.

Forged vs. Cast – What’s the Difference?

Differences Between Forging and Casting Metal

Forging and casting are two very different manufacturing processes used to manipulate the shape of metal. In the casting process, metal is heated until molten. Then it is poured into a mold or vessel to create a desired shape. In the forging process, material is pressed or hammered into a certain shape while still maintaining a solid state. So why do we choose to forge?

Forging is stronger than casting.

One of the main reason we choose to provide forging services is that it provides a stronger end product for our partners. According to a study performed by the Industrial & Manufacturing Engineering Department at the University of Toledo:

· Forged parts had a 26% higher tensile strength than the same cast parts.

· Forged parts had a 37% higher fatigue strength resulting in a much longer lifespan than cast parts.

· Cast iron only had 66% of the yield strength of forged steel, a measurement that indicates the load amount metal can hold before deforming.

· The forged parts had a 58% reduction in area when pulled to failure, compared to 6% reduction for cast parts. That means forge parts allow for much greater deformation before failure than cast parts.

Why is this?

When you melt metal, the grain size is free to expand. This creates a final product with a more random grain structure. A more random grain structure leads to deceased strength. The forging process keeps the grain structure tight and the product mechanically strong. There is also less need for expensive alloys to retain high strength.

Why use castings?

The main benefit of casting is to create components that are too large, complex, or otherwise unsuitable for the forging. We can forge part sizes up to 18” in length and weights up to 100 pounds. But if you are in need of an end product weighing 5000 pounds, casting would be a more suitable option. So use casting when:

· Your part is too large to forge.

· The part is complicated (contact us for advice on this)

· Part requires custom alloys added

Why use forging?

If your end piece is able to be forged, it should be forged. This will give your part better strength, more consistency, a tighter grain structure, and longer lifetime. Reach out to our engineers to see if forging is right for your project.

What is Press Forging?

Closed-Die Press Forging Explained

Press forging is a method of forming a piece of metal into a specific shape by applying gradual pressure on a shaped die holding the metal. In closed-die press forging, the metal is completely enclosed in a die and pressure is applied on the die. Compared to open-die press forging, closed-die is an overall more efficient method with lower chance of error.

With press forging, the metal is shaped in a uniform way from the surface to the center. This means the impressions created are cleaned and the end product is generally stronger. Tongs are usually not required, and draft angles are not as frequently used. Initial setup costs are also higher with press forging, but the method becomes more cost effective as volume increases.

Compared to drop forging, press forging has the advantage of being more cost effective for higher volume runs, and also results in a stronger workpiece. It also retains the strength benefits of forging compared to casting.

What is Drop Forging?

Closed-Die Drop Forging Explained

Closed-die drop forging is a process that hammers heated steel into a specific shape. This is done by placing a steel billet on a block as a hammer drops down making impact with the steel. With repeated blows, these impacts forge the steel into the shape of the mold.

While the drop forge process can utilize different types of forging hammers, the overall process remains relatively the same. Compared to press forging, drop forging has the advantages of being a faster process with lower inital setup costs. It also retains the strength benefits of forging compared to casting.