Basic Knowledge Points of Forging
Related machinery in the high load, severe working conditions of the important parts, and the simpler shape of the available rolled plate, profile, or welded parts, more forgings.
1. Deformation temperature
The beginning recrystallization temperature of steel is about 727℃, but 800℃ is commonly used as the division line, higher than 800℃ is hot forging; between 300 and 800℃ is called warm forging or semi-hot forging, forging at room temperature is called cold forging. Forgings used in most industries are hot forging, warm forging, and cold forging are mainly used in the forging of parts for automobiles, general machinery, etc. Warm forging and cold forging can be effective in saving materials.
2. Forging categories
As mentioned above, according to the forging temperature, it can be divided into hot forging, warm forging, and cold forging. According to the forming mechanism, forging can be divided into free forging, die forging, lapping ring, and special forging.
1) Free forging
It refers to the processing method of forging parts with simple general-purpose tools or directly applying an external force to the billet between the upper and lower anvils of the forging equipment to deform the billet and obtain the desired geometric shape and internal quality. The forgings produced by the free forging method are called free forgings. Free forging is mainly used to produce forgings in small batches, and forging equipment such as forging hammers and hydraulic presses are used to shape and process the billet to obtain qualified forgings. The basic free-forging process includes upsetting, drawing, punching, cutting, bending, twisting, shifting, and forging. Free forging is all hot forging.
Die forging is also divided into open-die forging and closed-die forging. Metal billet in a certain shape forging die chamber pressure deformation and obtain forgings, die forging is generally used for producing small weight, a large batch of parts. Die forging can be divided into hot die forging, warm forging, and cold forging. Warm forging and cold forging are the future development direction of die forging but also represent the level of forging technology.
According to the material points, die forging can also be divided into ferrous metal die forging, non-ferrous metal die forging, and powder products molding. As the name implies, the materials are ferrous metals such as carbon steel, copper, aluminum, and other non-ferrous metals and powder metallurgical materials.
Extrusion should be classified as die forging, which can be divided into the heavy and light metal extrusion.
Closed die forging and closed upsetting belong to the two advanced processes of die forging; as there is no flying edge, the utilization rate of the material is high. It is possible to finish complex forgings in one process or several processes. Since there is no flying edge, the force area of the forging is reduced, and the required load is also reduced. However, care should be taken to keep the billet completely unrestricted. For this reason, the volume of the billet should be strictly controlled, the relative position of the forging die should be controlled, the forgings should be measured, and efforts should be made to reduce the wear of the forging die.
Ring lapping refers to producing ring-shaped parts of different diameters through special equipment ring lapping machines, also used to produce wheel-shaped parts such as automobiles and train wheels.
Special forging, including roll forging, wedge cross-rolling, radial forging, liquid die forging, and other methods, are more suitable for producing certain special-shaped parts. For example, roll forging can be used as an effective pre-forming process, significantly reducing the subsequent forming pressure; wedge cross-rolling can produce steel balls, drive shafts, and other parts; radial forging can produce large barrels, step shafts, and other forgings.
According to the movement of the forging die, forging can be divided into pendulum rolling, swivel forging, roll forging, wedge cross-rolling, ring rolling, and inclined-to-roll. Fine forging can also process pendulum rolling, pendulum swivel forging, and ring rolling. Roll forging and cross-rolling can be used to pre-process thin material to improve material utilization. Like free forging, rotary forging is also partial forming, which has the advantage of being able to be formed with less forging force compared to the forging size. In this type of forging, including free forging, the material expands from near the die surface to the free surface during processing, making it difficult to ensure accuracy. Therefore, by controlling the direction of the forging die movement and the rotary forging process with a computer, products with complex shapes and high accuracy can be obtained with lower forging forces, such as producing turbine blades and other forgings with wide varieties and large sizes.
Forging equipment die movement and degrees of freedom are inconsistent and can be divided into the following four forms:
- Restricted forging force form: hydraulic presses with the direct drive of the ram by oil pressure.
- Quasi-stroke limiting form: hydraulic presses with oil pressure driving the crank linkage mechanism.
- Stroke limiting method: Mechanical presses with crank, connecting rod, and wedge mechanism driving the ram.
- Energy limiting method: Screw and friction presses utilizing a screw mechanism.
To obtain high precision, care should be taken to prevent overloading at the lower dead center and to control the speed and die position. These can impact forging tolerances, shape accuracy, and dolly life. In addition, attention should be paid to measures such as adjusting the slide guide clearance, ensuring rigidity, adjusting the lower dead point, and using subsidized transmission devices to maintain accuracy.
There is also the vertical and horizontal movement of the slide (the forging of slender parts, lubrication and cooling, and the forging of parts produced at high speed), and the use of compensation devices can increase the movement in other directions. The forging force, process, material utilization, output, dimensional tolerances, and lubrication and cooling methods are all different, and these factors also affect the level of automation.
3. Forging materials
Forging materials are mainly carbon steel and alloy steel of various compositions, followed by aluminum, magnesium, copper, titanium, etc., and their alloys. The material’s original state is a bar, ingot, metal powder, and liquid metal. The ratio of the cross-sectional area of the metal before deformation to the cross-sectional area after deformation is called the forging ratio. The correct choice of forging ratio, reasonable heating temperature and holding time, reasonable starting forging temperature and final forging temperature, and reasonable deformation and deformation speed are relevant to improving product quality and reducing costs.
Generally, small and medium-sized forgings are made of round or square bars as billets. The grain organization and mechanical properties of the bar are uniform and good, the shape and size are accurate, the surface quality is good, and it is easy to organize mass production. If the heating temperature and deformation conditions are reasonably controlled, forgings with excellent performance can be forged without large forging deformation.
Ingots are only used for large forgings. Ingot is cast organization, with large columnar crystal and open center. Therefore, it must be broken into fine grains by large plastic deformation and compacted loosely to obtain excellent metal organization and mechanical properties.
The powder metallurgy preform billets are pressed and sintered, and powder forgings can be made under hot conditions by die forging without flying edges. The forging powder is close to the density of general die forgings, with good mechanical properties and high precision, which can reduce the subsequent cutting process. Powder forgings have uniform internal organization, no segregation, and can be used to manufacture small gears and other workpieces. However, the powder price is much higher than that of general bars, and the application in production is somewhat limited.
By applying static pressure to the liquid metal poured in the death chamber and making it solidify, crystallize, flow, deform plastically, and shape under pressure, a die-forged part of the desired shape and properties can be obtained. Liquid metal dies forging is a forming method between die casting and die forging, especially for complex thin-walled parts that are difficult to form by general die forging.
In addition to the usual materials and aluminum, magnesium, copper, titanium and their alloys, iron-based high-temperature alloys, nickel-based high-temperature alloys, and cobalt-based high-temperature alloys of deformation alloys also use forging or rolling to complete. Still, these alloys are relatively narrow because of their plastic zones so forging will be difficult; different materials have strict requirements for heating, opening, and final temperatures.
4. Process flow
Different forging methods have different processes, including the longest process of hot die forging; the general sequence is: forging billet feeding; forging billet heating; roll forging preparation; die forging forming; cutting edge; punching; correction; intermediate inspection, an inspection of forging dimensions and surface defects; forging heat treatment, to eliminate forging stress, improve metal cutting properties; cleaning, mainly to remove surface oxidation; correction; inspection, general forgings to After the appearance and hardness inspection, important forgings should also undergo chemical composition analysis, mechanical properties, residual stress and other tests and non-destructive testing.
5. Forgings characteristics
Compared with castings, the metal can improve its organization and mechanical properties after forging processing. Casting organization after forging method of thermal processing deformation due to metal deformation and recrystallization, so that the original coarse dendritic and columnar grains into fine grains, uniform size of the equiaxial recrystallization organization, so that the ingot within the original segregation, loosening, porosity, slag, and other compaction and welding, the organization becomes more compact, improve the plasticity and mechanical properties of the metal.
The mechanical properties of castings are lower than the mechanical properties of forgings of the same material. In addition, forging processing can ensure the continuity of metal fiber organization so that the fiber organization of forgings and forging shape to maintain consistent metal flow line integrity can ensure that the parts have good mechanical properties and long service life using precision die forging, cold extrusion, warm extrusion, and other processes to produce forgings, are incomparable to castings.
Forgings are objects where metal is applied pressure to shape the required shape or suitable compression force through plastic deformation. This force is typically achieved through the use of a hammer or pressure. The forging process builds delicate grain structures and improves the physical properties of the metal. In the real-world use of parts, a correct design enables the flow of particles in the direction of the central pressure. Casting is a metal-forming object obtained by various casting methods, i.e., the smelted liquid metal is injected into a pre-prepared cast shape by pouring, pressure injection, inhalation or other casting methods, cooled, and after sand-fall, cleaning, and post-treatment, the resulting object has a certain shape, size, and properties.
Where to Buy Forgings: Your Ultimate Guide to Finding the Best Suppliers Introduction
When purchasing forgings, several factors should be considered to ensure you receive the highest quality products at the best possible price. You can make a well-informed decision that best meets your needs by evaluating material specifications, quality assurance, lead time and delivery, and pricing.
Selecting the appropriate material for your forging project is crucial, as it will directly impact the performance and durability of the finished product. Consider the specific requirements of your application, such as strength, resistance to wear, and corrosion resistance. Common materials used in forgings include steel, stainless steel, aluminum, titanium, and nickel alloys. Consult with a professional to determine the most suitable material for your project.
When selecting a forging supplier, verifying their quality assurance processes is essential. A reputable supplier will have a robust quality management system, including certifications such as ISO 9001 or AS9100. These certifications indicate that the supplier adheres to industry standards and has established systems for maintaining quality control throughout manufacturing.
Lead Time and Delivery
The lead time and delivery schedule are vital when purchasing forgings. Assess the supplier’s ability to meet your required delivery date, considering factors such as order volume, material availability, and production capacity. Inquire about their shipping options and any additional costs associated with expedited deliveries.
Pricing is critical when buying forgings—request quotes from multiple suppliers to compare costs and ensure you receive a competitive price. Remember that the lowest price may sometimes equate to the best quality, so weigh all factors before making your final decision.
Top Forging Suppliers
To help you identify the best forging suppliers, we’ve compiled a list of top domestic and international sources.
When sourcing forgings, consider partnering with domestic suppliers. These manufacturers can offer shorter lead times, lower shipping costs, and a better understanding of local regulations and industry standards. Working with a domestic supplier can also help you support your local economy and foster stronger business relationships.
International forging suppliers can offer competitive pricing and various material options. When working with an international supplier, consider language barriers, time zone differences, and import/export regulations. It’s essential to thoroughly vet any international supplier to ensure that they meet your quality and delivery requirements.
Trade Shows and Industry Events
Trade shows and industry events are excellent opportunities to connect with forging suppliers and gather valuable information about their products and capabilities. Attendees can view product demonstrations, engage in face-to-face discussions with potential suppliers, and learn about industry trends and innovations.
Local Distributors and Retailers
Local distributors and retailers can provide immediate access to forgings and related materials. They often stock standard forgings and can facilitate custom orders if necessary. By working with a local distributor, you can benefit from personalized customer service, reduced shipping costs, and faster delivery times.
Consider custom forgings if your project requires a unique shape, size, or material unavailable off the shelf. Custom forgings are manufactured to your precise specifications, ensuring the final product meets your requirements. Work with a reputable supplier experienced in custom forgings to ensure your project is completed to the highest quality standards.