The Most Common Types of Forging Defects

forging provides the best mechanical properties out of all manufacturing processes, but that doesn’t mean it’s faultless. Defects are common in forging, and most of them occur due to preventable errors or faulty processes. Let’s look at some of the most common types of forging defects and how you can prevent them in your foundry.

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Unfilled Section

As the name implies, this defect is when sections of the product remain unfilled. It can occur for a few different reasons. Poor die design, improper technique, insufficient heating, and lack of raw material are the most common culprits. You can eliminate or reduce instances of this defect by improving the die design, ramping up the heat, and using more material.

Cold Shut

A cold shut defect is when small cracks appear at the corners of the workpiece. Its usual causes include poor die design, sharp corners, or excessive chilling of the workpiece. To avoid a cold shut, all you need to do is increase the fillet radius of the die.

Scale Pits

Scale pits are also some of the most common types of forging defects. They’re small cracks or holes in the metal that occur due to improper cleaning of forged surfaces.

Scale pits are a common defect in forging operations that occur in an open environment. To prevent them, take care to clean the surface thoroughly.

Die Shift

Die shift is when the upper and lower dies are incorrectly aligned. This defect causes improper workpiece dimensions.

The fix is simple—you just need to ensure the dies correctly align before you forge. To achieve proper alignment, place one half of the workpiece on the upper die and the other half on the lower die before pressing them together.

Flakes

Flakes occur when the workpiece cools too rapidly. This reduces the strength of the forged product and causes it to deteriorate. Slowly cooling the workpiece should keep it from flaking.

Surface Cracking

Surface cracking is another temperature-related defect. It occurs when the forging operation takes place at low temperatures, which causes the metal to crack. The solution is to work at a higher temperature.

Another way to prevent defects in your forging operations is to invest in forging automation. By automating your foundry, you can ensure forging conditions are optimal every time. Additionally, you can cut down on imperfections in your products. To learn more about automating your foundry, contact CSD today!

Metal Forging Methods Explained

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Manufacturing Marvels Trenton Forging

Understanding the Different Metal Forging Methods

Manufacturing Marvels Trenton Forging

Forging is a manufacturing process that many industries rely on. In fact, hundreds of forged components can be found in aircraft, vehicles, farming equipment, trains, mining machinery, and more. When compared to other processes, like casting and fabrication welding, forgings are stronger and more reliable. Additionally, because the metal forging process can produce complex geometries efficiently, it can be a more cost-effective manufacturing process.

One common misconception is that forging is one universal method; in reality, there are several methods that a forging manufacturer may use. In general, forging can be classified in two ways: by the tooling and by temperature.

In this article, we’ll cover each forging method, as well as highlight the main types of equipment used in forging.

Let’s start with the first classification: forging by tooling

Forging by Tooling

The words “die” and “tooling” are often used interchangeably in the forging industry. They refer to the device that is used to shape a (usually pre-heated) billet, ingot, preform, or bar. When comparing forging by the tooling that is used, there are three primary methods: impression die, open die, and rolled ring.

Impression Die Forging

With impression die forging, metal is squeezed/compressed between two custom dies that each have pre-cut profiles/cavities (or impressions) of the final part shape. 

Then, using various types of equipment, like a mechanical press or a drop hammer, the billet or preform is compressed while it undergoes plastic deformation. In each impression, the workpiece is forced into the cavity as the flash (excess metal) flows out into the die. As the flash cools, pressure builds up in the impression which helps ensure a more uniform component. Then, the flash is removed either manually or with trimming dies.

Impression die forging is primarily used for manufacturing complex symmetrical and asymmetrical forged components. This method can also achieve closer tolerances when compared to open die forging.

Open Die Forging

In open die forging, a workpiece (ingot, bar, billet, or preform) is deformed between an upper and lower flat-faced die, and the movement of the workpiece itself is largely what helps shape the final part. 

In addition to flat-faced dies and hammers (or presses), there are other tools that can be used in open die forging, including saddles, blocks, rings, mandrels, and punches.

The components made in open die forging are usually simple in shape (long and rectangular, flat and round, etc.) and can be further machined after the forging process. 

Open die forging is used to produce components of all sizes, but, when it comes to complexity, impression die forging is usually the preferred method over open die forging.

Rolled Ring Forging

The last method by tooling is rolled ring forging. Unlike impression die and open die, the roll forging method does not utilize dies, and it is used to make very specific shapes: rings. 

This forging process can be used to make all types and sizes of seamless rings. Roll forging is preferred over machining, cutting, and casting because it can produce components to tight tolerances. Additionally, forging eliminates internal porosity, unlike casting, which reduces creep, fatigue, and other issues.

In roll forging, the stock is usually preformed. The preform technique used in roll forging is called punching. As the name implies, a hole is punched into the stock, creating a donut shape. Then, the preform is run through a rolling mill until the final component is produced.

All types of components can be created by roll forging, including engine bearings, wheel bearings, flanges, and gears.

Forging Processes by Temperature

Metal forging processes can also be categorized by the actual temperature of the workpiece. Different temperatures affect the plasticity of the metal, the final quality of the piece, and can determine many of the component’s final mechanical properties, including strength, ductility, and resistance to impact or fatigue.

When categorizing forging by temperature, there are three primary methods: hot, warm, and cold.

Hot Forging

In hot forging, typically the dies/tooling are pre-heated to a specific temperature and then the workpiece itself is heated to a predetermined temperature. The temperature used in hot forging varies based on the raw material being used, the component that is being produced, and any specific application requirements.

In hot forging, heat makes the metal more ductile, and the consistent pressure of the dies squeezing hot metal produces a more refined grain structure and thus stronger, more ductile components.

Warm Forging

In warm forging, a workpiece is heated within a specific range: above work hardening temperature, but below the scaling temperature. 

Warm forging covers a range of forged products that do not require the expense and tight tolerances of cold forging or the higher strength yield of hot forging. Warm metal forging is typically used for parts that are already close to their final shape, such as shafts and gears.

Cold Forging

Want more information on ODM copper forgings? Feel free to contact us.

As the name suggests, the cold forging process is performed at cooler temperatures (anywhere between room temperature to just a few hundred degrees). 

Cold forging also utilizes other processes including bending, coining, rolling, and extruding, depending on the type of component that is being produced. The metal used in the process is also typically annealed or softened during the forging process, and continuous lubrication is required during this process to prevent frictional heat. 

Although cold forging is extremely precise, and often requires little to no finishing work, hot forging is still the preferred method for complex, custom forgings. Additionally, components that are cold-forged are more likely to contain residual stresses, which can eventually lead to cracking, warping, and other issues. 

Equipment Used in Forging

If you ever see or hear terms like press forging or hammer forging, this is referring to the type of equipment being used during a particular forging process.

Presses

During open die or impression die forging, manufacturers may use a press, which allows for the controlled deformation of a workpiece through high pressure. There are several types of presses: screw, hydraulic, and mechanical. 

A screw press drives a power ram up or down on a screw shaft to press-form metal. A hydraulic press uses a cylinder under hydraulic oil pressure, and a mechanical press is actuated by a gear, lever, or other mechanical operator connected to a motor and a crankshaft.

Drop Hammers

Next, a drop hammer, as the name implies, uses the power of a heavy metal hammer that when dropped from a height (gravity-powered) or power-assisted, will strike the workpiece. The powerful blow releases kinetic energy to deform the metal, and typically about three blows at each stage is enough to shape the molten metal, although this number can vary.

Counterblow Hammers

For very large metal parts, a counterblow hammer imparts high-impact energy of a tonnage hammer onto a die. The hammer moves in opposite directions with each blow and offers more precise formation of large forgings. Counterblow hammers may be operated by hydraulic or pneumatic drive systems.

Ring Rollers/Rolling Mills

A ring roller, rolling mill, or reduction mill is mostly used in seamless rolled ring forging, but can also be used to preform stock during open die or impression die forging. In the rolling mill, a preform is passed through the machine’s rolls, which then shapes the final component (additional machining of the component may be required after it passes through the rolling mill). Some rolling mills even include a manipulator, which is used to punch the stock.

Is One Forging Method Better Than the Other?

There is no particular forging method that is inherently “better” than the other. Each will have unique advantages depending on the size, shape, and quantity of components, the complexity of the forged parts, or any demanding strength or mechanical properties.

Some part geometries are also better suited to certain processes and equipment. In one of our previous articles, we’ve highlighted some of the many benefits of each forging process. Click here to learn more about the advantages of each process.

Have Questions? Contact Trenton Forging Today

Trenton Forging is a U.S.-based forging manufacturer that specializes in both hot forging and impression die forging. We are capable of producing both symmetrical and asymmetrical custom components from steel, stainless steel, and steel alloys. Some of our other capabilities include prototyping and reverse engineering, custom tooling, and machining. 

If you have general questions about our metal forging process, or would like to request a quote, fill out our online form today.

What Are the Different Types of Forging Processes?

When you picture blacksmithing, you might picture a certain workspace and tools. Many people think of historical blacksmiths even though blacksmithing still takes place today. Modern tools and equipment have made distinct types of techniques available to today’s metalsmiths. Keep reading to learn more about the different types of forging processes, the tools involved with each technique, and some of their applications.

Forging Equipment-Based Processes

Forging types and techniques are dependent on what types of tools the blacksmith has on hand. Any blacksmith can use hammering techniques with just a few simple tools, but more advanced techniques, such as die forging, require industrial-level equipment. Keep reading to learn the basics of equipment-based forging techniques and some of their applications.

Hammer Forging

Hammer forging is the most traditional form of blacksmithing and one that many professional and hobbyist smiths still practice today. This method requires simple and traditional tools: a hammer and an anvil. These tools have become synonymous with blacksmithing as a craft. They are also affordable, making hammer forging an ideal method for entry-level blacksmiths. However, hammering can also be an advanced process, especially when you consider the endless types of hammers and hammering techniques blacksmiths can learn.

However, some professional smiths and manufacturers have upgraded this process, using modern technology and automation to power the hammering techniques. Examples of these modern hammering techniques include gravity drop and power drop hammers.

Gravity drop hammers: The hammer ram connects to a belt, chain, board, and piston to create several types of dropping systems. When a smith lifts and drops the hammer, it is accelerated by gravity, providing additional force to the blow.

Power drop hammers: Power drop hammers feature another force behind the hammering motion, such as steam power, cold air, or hot air pressure. This provides additional force behind the hammering ram’s acceleration and drop, creating stronger hammering motions.

Press Forging

Press forging is another equipment-based blacksmithing process that revolves around using a press. There are two main types of press for forging and manufacturing: the mechanical and the hydraulic presses. This type of equipment works by continuously squeezing the metal down to form a solid shape. Mechanical presses are the more traditional model, as they operate with toggles and hand cranks to produce a standard press. Hydraulic presses are more common in manufacturing applications, though some professional craftsmen may use them as well. Hydraulic presses use pressure to bend and shape material. Many hydraulic presses are automated, which means they use power and programming to perform repeated forging actions.

Temperature-Based Forging

Outside of the equipment you use for forging, there are other conditions that affect the forging process, such as temperature. The temperature of your working materials can have a significant impact on your forging process and final product. Any blacksmiths interested in forging need to learn how to control the temperature of their workpieces through temperature-based forging methods.

Cold Forging

Cold forging is the process of working with a material at room temperature. This method is ideal for soft metals and other materials, such as aluminum, tin, lead, and copper. Because these metals are soft and malleable, they are easy to work with even without influencing their temperature, which is where warm and hot forging would come in. Cold forging is ideal for beginner blacksmiths because it doesn’t require a heat source—all you need is an anvil, hammers, clamps, and soft metals. Beginner smiths can practice hammering and other forging techniques through cold forging.

Warm Forging

Warm forging is how blacksmiths start to influence the properties of a metal by heating it. During warm forging, blacksmiths will set their heat source to unique temperatures for unique metals; heating steel is a good example that takes place at 700 to 800 degrees Fahrenheit. Heating the metal to this temperature allows a smith to work with other metals outside the softer varieties, such as steel and harder alloys. It also promotes higher production rates and stronger materials.

Hot Forging

Hot forging involves using elevated temperatures to easily deform metals. Hot forging allows smiths to use the widest variety of materials and shape metals quickly and easily. However, only experienced smiths usually handle hot forging because repeated heat and hammering can weaken the working material. Advanced blacksmiths must use a combination of cold forging and hot forging techniques to strengthen their final pieces.

Die-Based Processes

The die forging process involves placing metal between a custom-shaped die, or impression. Die forging is a common technique in manufacturing, though it can also be useful for blacksmiths creating decorative pieces and stamped materials. If you’re looking for a way to create repeated shapes and patterns, consider the die forging process.

Open-Die Forging

Open-die forging is the process of flattening a piece of metal between two flat dies or surfaces. Some machines will even flip an impression and use the even side to flatten the metal. This creates a rough shape for further forging processes. This technique is commonly used after hot forging a piece of metal so that a smith can easily flatten or shape the material.

Closed-Die Forging

Closed-die forging is similar to press forging, as it uses a set of shaped impressions to create a form for the workpiece. This method also uses heated metals that can form to the unique shape of the impression. The two impressions create a cavity that the metal will shape to and form a unique piece. This is a common process in manufacturing, especially for repeatedly creating specific parts. However, it is an advanced method that requires careful control of material temperatures, volumes, and die designs.

Now that you’re more familiar with the different types of forging processes, you can use this knowledge to decide how you want to pursue blacksmithing. If you want to practice the craft in the most traditional sense, all you need is a hammer and an anvil to get started. However, you can also adopt some modern technology and forging techniques to make the process easier. For example, browse our selection of propane forge burner kits at Cast Master Elite to see how modern advancements can make blacksmithing easier and more accessible for anyone, whether you’re a hobbyist or a professional smith.

Copper, known for its excellent electrical and thermal conductivity, has been a vital component in various industries for centuries. In this blog post, we will delve into the world of Copper 101, focusing specifically on its machinability aspects. We'll explore the properties that make copper a popular choice for numerous applications, and provide valuable insights on how to machine this versatile metal efficiently.

Understanding Copper 101

Copper 101, also known as Oxygen-Free Electronic (OFE) copper, is a high purity copper with a minimum copper content of 99.99%. This grade of copper is primarily used in applications where high electrical and thermal conductivity is crucial. Some common applications include electrical connectors, waveguides, and bus bars.

Machinability of Copper 101

Copper, in general, is known for its relatively low machinability compared to other metals like steel or aluminum. However, with the right techniques and tools, it can still be machined effectively. Copper 101, in particular, has a machinability rating of 20%, which means it requires more effort and specialized techniques to achieve a smooth finish.

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Tool Selection

When machining copper, it's essential to use sharp, high-quality tools made of materials like carbide or high-speed steel (HSS). These materials are more resistant to wear and can withstand the heat generated during the machining process. Additionally, using tools with a positive rake angle can help reduce cutting forces and improve chip evacuation.

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Cutting Speeds and Feeds

Since copper is a soft and ductile material, it can easily become deformed or smeared during machining. To avoid this, it's essential to use appropriate cutting speeds and feeds. For Copper 101, a cutting speed of 200-300 surface feet per minute (SFM) and a feed rate of 0.002-0.004 inches per revolution (IPR) are recommended.

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Lubrication and Cooling

Copper tends to generate heat during machining, which can cause the workpiece and tool to overheat. Using appropriate lubrication and cooling methods can help minimize heat buildup and improve the overall machining process. Flood cooling with water-soluble oil or applying a mist coolant can be effective in reducing heat and prolonging tool life.

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Chip Control

Proper chip control is crucial when machining copper, as it helps prevent the formation of long, stringy chips that can damage the workpiece and tool. Using tools with chip breakers or opting for climb milling can help break chips into smaller pieces, making them easier to evacuate.

Conclusion

Machining Copper 101 may be challenging due to its low machinability rating, but with the right techniques and tools, it can be done effectively. By understanding the properties of Copper 101, selecting appropriate tools, and following guidelines for cutting speeds, feeds, lubrication, and chip control, you can successfully machine this versatile metal for various applications.