Heat treatment is a process that major industries use today in generating different parts and products. Mostly used in metals, this process can easily alter the physical properties of the materials. It can even change the chemical composition of the materials. Some properties that heat treatment can change are ductility, hardness, wear resistance, elasticity, and toughness.
This process, however, can only provide the alteration needed by industries once manufacturers have secured the right tools and equipment pieces. One of the tools that manufacturers must use in heat-treating metal workpieces is furnaces. Furnaces are often utilised to effectively heat and then cool workpieces to achieve properties that manufacturers have specified.
Many types of furnaces can be used in heat treatment processes. They can be categorised based on the positioning of the workloads as well as how they interact with the interior atmosphere. Some types of furnaces that are used in heat-treating workpieces are as follows.
Batch Furnaces
Batch furnaces can process different metal workpieces for long periods of time. The work charge with these furnaces remains stationary, ensuring that interactions with changes in their atmosphere can be carried out in near-equilibrium conditions. Varying types of batch furnaces can be used by manufacturers. These types include bell furnaces, box furnaces, fluidised bed furnaces, pit furnaces, and salt pot furnaces. Integral quench furnaces, in particular, are common batch furnaces that can perform case hardening to metal workpieces.
Continuous Furnaces
Continuous furnaces, alternatively, often work by allowing the workpieces to move in specific manners while the environment surrounding them changes. Some common types of continuous furnaces that manufacturers take advantage of include mesh belt furnaces, rotary drum furnaces, humpback furnaces, vacuum furnaces, and walking beam furnaces. One common type of continuous furnace today is the pusher furnace. This type of continuous furnace can be effective in carrying out hardening, stress relieving, annealing, and carburising.
Atmosphere Furnaces
Atmosphere furnaces take advantage of a protective atmosphere to surround the workpieces whenever they are heated and cooled. When picking the volume of the protective atmosphere, manufacturers have to consider the type and size of the furnace, the presence or absence of doors or curtains, the environment, size, loading, and nature of the work.
By picking the right atmosphere furnaces, the success of a heat treatment process can be achieved. The atmospheres used in heat treatment, after all, intend to protect the workpieces from surface reactions and allow their surfaces to change or be chemically active or reactive.
Vacuum Furnaces
Vacuum furnaces can be designed based on the size of the workpiece, the pressure and temperature to be attained, and the medium that will be used in cooling the workpieces. And during heat treatment, they should be able to control the temperature and vacuum level optimally to process workpieces optimally. Some parts of vacuum furnaces are the vessel, the pumping system, the hot zone, and the cooling system. These furnaces can be effective in carrying out annealing, sintering, brazing, and other similar heat treatment processes.
Many more furnaces can be used in heat treatment processes. However, the furnaces listed above are some of the most common elements used by manufacturers today.
Metals, in general, are materials that can be prepared, polished, or fractured to showcase a lustrous appearance. They can also be processed further to alter their physical properties such as strength, ductility, malleability, and conductivity to electricity and heat.
Many types of metals can be maximised by various industries. One of these metals is carbon steel. Carbon steel, also called mild steel, is a steel integrated with carbon, iron, and other elements. It is often used in buildings, bridges, shafts, rails, pipelines, cars, fridges, and washing machines. It can even be utilised in making blades, cutting tools, punches, and dies.
But before industries can utilise carbon steels in making various parts and products, these materials should undergo heat treatment techniques first.
The Basics of Heat Treatment
Heat treatment manipulates the molecular structure of a metal and changes its properties. This process can either increase or decrease the ductility, toughness, hardness, and yield strength of metal without changing its electrical and thermal conductivity. Generally, heat treatment has four states. These states are annealing, normalising, hardening, and tempering.
Annealing is responsible for altering the physical and chemical properties of a metal. It ensures that the ductility of a material will increase while its hardness is reduced to make it more workable. Normalising, alternatively, removes impurities and improves the ductility and toughness of a metal workpiece. It is done by heating the material between 750-980°C.
Hardening is another heat treatment state that metals can undergo. It also involves heating the material to a high temperature, holding it at a certain temperature for one hour per inch of thickness, and cooling the material quickly. Its goal is to make the material boast a harder, stronger structure. Tempering, ultimately, enhances the toughness of metals so they can hold up during subsequent processing. It is done by heating the metals to a high temperature below their melting point and cooling them in the air.
Heat Treating Carbon Steels
Carbon steels, fortunately, are easy to process as their molecular structure is crystalline. Hence, they can undergo a heat treatment process to alter their properties. These metals can be exposed to various ranges of specific temperatures for a specific amount of time. Once exposed to various temperatures, their structure is expected to change, altering their shape or phase.
As experts hold or soak the carbon steels in hot and cool temperatures, the shape of their crystalline structure will further change.
Now, carbon steels can contain several phases, exhibiting their own set of properties. These phases include austenite, ferrite, cementite, banite, martensite, and pearlite. These phases can make carbon steels softer, harder, or tougher, making them highly recommended for a wide range of industrial applications.
But to make heat treatment successful, carbon steels should be oil quenched. Using water, after all, may only produce cracks in the workpieces. It is also important to take note that their carbon content can dictate the speed of their quench. The lower the carbon, the faster and more aggressive their quench must be. To know more about heat-treating carbon steels, you can contact us at Alpha Detroit Heat Treatment.
Metal parts and products have been dominating a wide range of industries due to the benefits they bring. They are durable and robust, allowing them to last for a long time. They can also be customised, which grants industries the opportunity to maximise them based on their needs.
But before these parts and products can be distributed to the end-users, a lot of them must undergo heat treatment first. Heat treatment is a process wherein metals are heated and cooled using a wide array of methods, making sure that they obtain the desired properties of the clients. Manufacturers can subject ferrous and non-ferrous metals to heat treatment, as long as the right methods are maximised.
Primary Benefits of Heat Treatment
Tons of benefits are expected with heat treatment. First, it can alter the properties of the metal workpieces. Some methods can boost the hardness of the metals. Others, alternatively, can make the materials soft. Heat treatment methods can likewise affect the heat and electrical conductivity of select metal materials.
Another benefit of heat treatment is it can relieve stresses on metal materials. Metal materials can experience stress whenever they are subjected to a load or force. These instances can then distort or deform them. Heat treatment methods, fortunately, do not introduce stresses to the materials. Instead, they ensure that the workpieces will remain as intact as possible.
Other improvements expected with heat treatment include enhanced strength, improved wear resistance, and reduced brittleness.
Heat Treatment Common Methods
A wide array of heat treatment methods can be applied to various metals.
One of these methods is annealing. In this method, metal materials are heated beyond their upper critical temperature. They are then cooled slowly. The primary purpose of annealing is to soften the metal materials, allowing them to be workable for forming and cold working. It can also improve the ductility, machinability, and toughness of the materials.
Hardening is another heat treatment method that can be applied to metals. This method is carried out to enhance the hardness of metal workpieces. It is done by heating the metals to a specified temperature before cooling them rapidly. The cooling part is done by submerging them into a cooling medium like brine, oil, and water.
Stress relieving and tempering are two more methods that can be done to metals. Stress relieving is carried out by subjecting metals to a temperature below their lower critical limit. They are then cooled slowly. Its main purpose is to relieve stresses that may have been obtained by the metals due to past processes like machining, rolling, and others Tempering, ultimately, is a process that can reduce excess hardness obtained during hardening.
The Essence of Heat Treating Steel
Steel is considered to be one of the most common metal materials globally. It is an alloy made from iron and other elements. These elements include aluminium, carbon, manganese, oxygen, nitrogen, phosphorus, sulphur, and silicone. The ratio of these elements can often determine the hardness, flexibility, durability, and other steel properties.
The primary reason steel should be heat treated is it is often used in a wide range of applications. Since not all applications are similar, steel workpieces may have to boast various qualities. Heat treating, fortunately, can alter the mechanical properties of steel based on one’s needs. Some methods used for processing steel are annealing, quenching, tempering, and hardening. To help you process steel, you can contact us at Alpha Detroit Heat Treatment.
Metal workpieces require delicate processes before they can achieve the properties needed by industries. One of the processes they must undergo is heat treatment.
Heat treatment is comprised of industrial, thermal, and metalworking methods that can alter the physical properties of metal workpieces. These methods may sometimes change the chemical properties of the same materials. Some properties of metal workpieces that are expected to improve during heat treatment are strength, hardness, ductility, elasticity, and wear resistance.
Many heat treatment methods can be maximised by manufacturers in processing metal workpieces. One of these methods is case hardening, particularly carbonitriding.
An Introduction to Carbonitriding
Carbonitriding is a part of the case hardening process, a heat treatment method wherein the surfaces of metal workpieces are enhanced. Case hardening often ensures that surfaces can be resistant to wear. It then preserves the toughness and strength of the core.
Given the general benefits of case hardening, it is not surprising for carbonitriding to provide the same thing. With the addition of nitrogen, carbonitriding can increase the wear resistance and surface hardness of metal workpieces as it generates a hardened surface layer over metals.
During the carbonitriding process, carbon and nitrogen atoms diffuse into metal workpieces. The diffusion of these things then creates barriers to the workpieces, increasing their hardness and modulus near their surface. Most of the time, this process is applied to metal workpieces made from low-carbon steel, which are mostly inexpensive and easy to machine.
The Specifics of Carbonitriding
To produce parts and products with more durable surfaces, certain conditions must be met during the process of carbonitriding. First, the process must be done at lower temperatures. It should also be carried out for shorter times, ensuring that components will not be prone to distortion. To reduce distortion further, less severe quenching media like oil can be used.
The temperature range of carbonitriding is between 820 and 900 degrees Celsius in a gaseous atmosphere. Around 0.5 to 0.8% carbon and 0.2 to 0.4% nitrogen can then be added to the surface of plain carbon steel or low alloy steel workpieces. Once the diffusion time is over, the components must then be quenched directly in oil. The case-hardened depth will often be around 0.7 mm. However, it can still vary depending on the hardening temperature, the hardenability of the steel, the quench rate, and the dimensions of the component.
Low-temperature tempering between 150 to 200 degrees Celsius is, ultimately, necessary to complete the carbonitriding process.
Carbonitriding Primary Benefits
Given the effects of carbonitriding on workpieces, this process can be utilised by industries that want products with hard and wear-resistant surfaces. In this case hardening method, it can easily improve the hardenability of the workpieces. Distortion is likewise reduced with carbonitriding as it can already be processed in lower temperatures.
The whole process of carbonitriding makes it effective in mass-producing small components. Keep in mind that the mild quenching speed must be reduced during processing to reduce the risk of cracking. Some products that can be processed through carbonitriding are gears, shafts, pistons, rollers, bearings, hydraulic levers, pneumatic systems, and mechanical systems.
Aside from low-carbon steel, carbonitriding can also be used for workpieces made from mild steels, low alloy steels with around 0.25% carbon, free-cutting steels, and sintered steels.
Heat treatment is a crucial process that manufacturers carry out in altering the properties of metal workpieces. It often features various industrial, thermal, and metalworking techniques to change the characteristics of materials. These techniques include quenching, tempering, annealing, hardening, and stress relieving.
With the right heat treatment techniques, manufacturers can expect improvements in the strength, hardness, ductility, toughness, and elasticity of their metal parts and products. They can even use these techniques to process glass and other similar materials.
But one particular type of metal that should be subjected to various heat treatment techniques is tool steels. They should undergo the right heat treatment techniques so they can boast great toughness, wear resistance, and heat resistance. Various types of tool steels must be heat treated carefully. Some of them are as follows.
Water Hardening Tool Steels
Water hardening tool steels often contain around 1% carbon and a tiny amount of vanadium for toughness and grain refining. When processing these materials, their depth of hardening should be around 3mm when quenched from a normal hardening temperature of 780°C. The hardening depth can then be increased to around 6mm when quenching at 870°C. As the quench temperature increases, their toughness will decrease.
When quenching water hardening tool steels, one may use cold water or 10% brine solution to reach their maximum hardness. Vigorous agitation is likewise needed to reach satisfactory quenching since a slow cooling rate can cause the formation of soft spots. Tempering these tool steels must then be carried out in the range of 150 to 250°C to attain the needed hardness.
These materials are often used in woodworking tools and cold-heading tools.
Oil Hardening Tool Steels
Oil hardening tool steels, alternatively, are materials that have been hardened from 800 to 840°C by quenching them into the oil. When heat treating these materials, they should be preheated first at 650 to 700°C. Doing this allows them to equalise at a subcritical temperature before raising them to their austenitisation temperature, making sure that they retain dimensional stability throughout their applications.
When tempering oil hardening tool steels, manufacturers should expose them to temperatures of 170 to 200°C. Their exposure to these temperatures can provide them with hardness over 60HRc. Once they are tempered in the range of 250 to 350°C, their impact strength can be significantly reduced, making them weak against external forces.
Oil hardening tool steels are perfect for heavy section punches than the W series tool steels as they possess good dimensional stability.
Air Hardening Tool Steels
Air hardening tool steels, ultimately, are tool steels with grades W and D of AS1239. They need to be preheated at 780°C before they undergo austenitising and hardening as they may be affected by still air cooling. Large sections of these tools may likewise need to be cooled in an air blast so they can attain maximum hardness.
These tool steels should be tempered when cooled to a handwarm condition. They may also require multiple tempering processes so they can transform and achieve maximum toughness.
If you need to acquire some heat-treated tool steels, you can contact us at Alpha Detroit Heat Treatment. We pride ourselves on providing quality service and reliability, especially in terms of your heat treatment needs.