Workpieces made from metals are often processed by manufacturers to ensure that they boast the needed properties of various industries. One process that they carry out is heat treatment.
Heat treatment is comprised of various industrial, thermal, and metalworking techniques to change the physical or chemical properties of metal workpieces. Some forms of heat treatments that manufacturers apply to metal workpieces are hardening, annealing, tempering, and case hardening. These heat treatment forms require various tools, elements, or apparatus to ensure that the changes expected to metal workpieces will be achieved.
One element that can be used to conduct these heat treatment processes is a salt bath. Any heat treatment process that has been carried out with a salt bath is called salt bath heat treatment.
Benefits of Salt Bath Heat Treatment
Salt bath heat treatment is a heat treatment technique that immerses treated metal workpieces into a molten salt or salt mixture. Tons of benefits are associated with salt bath heat treatment.
• Quick Heating: One of the benefits of salt bath heat treatment is it can provide quick heating to workpieces. Metal workpieces that have been immersed into molten salt or salt mixtures can be heated through conduction. And since heat will be transferred by the liquid media, the heat transfer rate is expected to be much speedier than other heating methods like radiation or convection through a compatible gas.
• Low Surface Oxidation: Another benefit of salt bath heat treatment is it can promise low surface oxidation to the treated parts. Whenever the workpieces are immersed in a salt bath, their exposure to the atmosphere is already minimised. This minimal exposure makes them protected from oxidation and damages associated with it.
• Controlled Cooling: One more benefit of salt bath heat treatment is it can control the cooling conditions of the heat-treated parts during quenching. Water or oil are often used as the quenching media for conventional quenching operations, which may cause cracks and distortions due to their high cooling rate. Cooling in molten salt, alternatively, can make the cooling slower. It even stops at low temperatures, avoiding any damage.
Salt Bath Heat Treatment Processes
Many heat treatment processes can be done in salt baths. Some of them are as follows.
• Quenching: Quenching is the process of cooling workpieces rapidly from their upper critical temperatures. Since molten salts can provide controlled cooling, they can save the parts from obtaining cracks and distortions.
• Martempering: Martempering is conducted by quenching a part in a quenching medium or molten salt. The part will then be left to reach a uniform temperature distribution before its bainite formation. This process is carried out in parts with temperatures above their martensite formation or austenite-martensite transformation.
• Austempering: Austempering is the isothermal hardening process wherein the workpiece is quenched in molten salt and is left to reach uniform temperature distribution. The workpiece will then be removed after the bainite formation has been completed.
• Carburising: Carburising is another heat treatment process that involves the diffusion enrichment of a part’s surface layer with carbon. This process is normally carried out at temperatures of 850 to 950 degrees Celsius.
Other salt bath heat treatment processes that can be useful for many industries are hardening, nitriding, carbonitriding, and deep brazing. For your salt bath heat treatment needs, feel free to contact us at Alpha Detroit Heat Treatment.
Manufacturing companies carry out many processes to ensure that they come up with high-quality parts and products out of durable materials. One of the materials they would often maximise and take advantage of is metal.
Manufacturers mainly utilise metals thanks to their accompanying strength, durability, cost-efficiency, and longevity. And with these qualities alone, they can easily provide industries such as automotive, electronics, food processing, and power their product needs. Now, one common thing about these industries is they would often subject metal parts and products to various conditions. As time passes, they might get damaged by the surrounding elements. Hence, they are recommended to be coated with a compatible surface treatment.
One surface treatment that manufacturers can maximise is black oxide coating.
Black Oxide Coating Quick Overview and Benefits
The black oxide coating is a surface treatment wherein metal parts and products are subjected to an electrochemical or chemical treatment, making their surfaces become matte black. During this process, manufacturers immerse workpieces in an alkaline aqueous salt solution, with temperatures reaching approximately 140 degrees Celsius.
The formation of the matte black finish is generated by the interaction between the iron component of ferrous metal alloys and the oxide bath. Their interaction produces magnetite, a compound that introduces the changes on their surface finish.
By subjecting parts and products to black oxide coating, their appearance is expected to improve. These parts and products can likewise achieve enhanced dimensional stability and reduced light reflection on their surface. Their thickness may even increase a little bit.
Factors to Consider before the Coating Process
If you are thinking of subjecting your metal parts and products to black oxide coating, you must consider the following factors first before opting for the said process.
• Desired Appearance: As mentioned earlier, metals that have been subjected to black oxide coating can boast improve appeal. But the appeal of the said parts can be subjective. And so, if you want to have parts and products with a matte black appearance, you can proceed with the black oxide coating. Alternatively, parts and products with glossy finish may have to be subjected to other processes.
• Protection Duration: Another factor you must consider before opting for black oxide coating is the required protection duration. This specific process can provide lengthy corrosion resistance properties to parts and components. However, if they will be used in a high-temperature environment, you may want to opt for other surface treatments as black oxide finish tends to wear off when exposed to the said environment condition.
• Environment: Black oxide finish, as previously stated, may not last for a long time if it is applied to parts that will be used in a high-temperature environment. Additionally, this finish may also wear off promptly once parts and products are exposed to specific levels of humidity and vapour. Only maximise this coating type if your parts and products will be used primarily indoors or at optimum temperature, humidity, and vapour levels.
Black oxide coating may have some limitations, but it can still be useful for components used in the automotive, military, medical, and electrical industries. To attain this surface treatment, you can contact us at Alpha Detroit Heat Treatment.
One common way of processing metal materials is through heat treatment. While metals already possess high-quality properties, they should still undergo heat treatment processes to further enhance their overall characteristics.
Heat treatment helps improve the qualities of metals as it heats the materials without reaching their molten phase. After heating them for a specific amount of time, the metals are subsequently cooled in a controlled way to achieve their desired mechanical properties. Some metals end up getting stronger, while others become more ductile. Heat-treated metals can also become more malleable and more resistant to abrasion.
Different heat treatment techniques can be carried out to process metals. One of these techniques is flame hardening.
Flame Hardening and Its Working Principles
Flame hardening is a surface-hardening process wherein a thin surface section of metal is heated rapidly. The heating application of the material is done by the direct application of the flame, boasting a temperature that is above the metal’s upper critical temperature. After exposing it to the said temperature, the metal is quickly quenched in oil or water. The quenching process turns austenite to martensite without affecting the core’s original soft state.
The high-temperature flame used in this process comes from the combustion of a fuel gas with air or oxygen. The hardened depth of the material may range between 0.8 and 6 mm, which would mostly depend on the fuel gas, air or oxygen, flame head design, heating duration, quenching medium, quenching method, and the hardenability of the metal.
Operating Variables for Flame Hardening
One of the operating variables for flame hardening is the distance between the flame’s inner cone and the surface of the material or component. The travel speed of the flame head or the component can also affect the success of the said heat treatment technique.
Other operating variables for flame hardening are oxygen to fuel gas ratio in the mixture, type and angle of the quench, and flame velocities.
All these variables should be controlled optimally by the professionals assigned to conducting this heat treatment technique.
Understanding Flame Hardening Methods
Various flame hardening methods can be carried out by heat treatment experts. These methods would normally have to consider the shape, size, and composition of the metal. They would also have to consider the area to be hardened, the desired depth of the hardened case, and the number of materials that will be hardened.
One of these methods is manual hardening. This method is done with the help of a welding torch, with the flame head boasting either a single orifice or multiple orifices. The spinning method is another flame hardening method that can be perfect for components like wheels, gears, and cams, which boast round or semi-round structures.
Progressive hardening is then used for components that cannot be hardened by the manual method. Shafts, rolls, and other long parts can, ultimately, take advantage of progressive spin hardening. This method combines spin hardening and progressive hardening.
Flame hardening, in general, can be useful for materials with any shape. It can also be used for numerous types of steels, large forgings, and castings without requiring expensive equipment pieces. To know more about this process, you can contact us at Alpha Detroit Heat Treatment.
Many industries today use metals in generating the parts and products they need. One reason why metals are often used by industries is they can be managed conveniently. And by applying the right processes, they can easily possess the properties they need.
One process that metals typically undergo is heat treatment. Heat treatment is a general process wherein metal materials are heated without allowing them to melt. They are then cooled in a controlled way, ensuring that they attain the desired mechanical properties. Some heat treatment techniques are meant to make them stronger, while others intend to make them malleable, more ductile, or more resistant to elements like abrasion.
Key Properties of Non-Ferrous Metals
One group of metals that undergo heat treatment is non-ferrous metals. Tons of products being used by industries and even households today are packed with non-ferrous metals. These metals do not possess iron in huge amounts, providing them better resistance to rust and corrosion compared to the ferrous ones. Another quality of non-ferrous metals is they have great malleability, which allows them to be shaped or extended without any issues. Ultimately, these metals are non-magnetic, making them useful for electronic and wiring applications.
Many metal elements belong to the non-ferrous classification. These elements include aluminium, lead, copper, tin, titanium, zinc, and lead. Copper alloys such as brass and bronze are also part of the non-ferrous classification. One common thing about these metal elements and alloys is they are all used in many residential, commercial, and industrial applications.
Bright Annealing Non-Ferrous Metals
Various heat treatment processes can be carried out on non-ferrous metals. But one distinct process that these metals can take advantage of is bright annealing.
Bright annealing is a heat treatment process wherein non-ferrous metals are subjected to a nitrogen-hydrogen atmosphere. When determining the proportion of hydrogen in the said atmosphere, workers would have to assess the material and process temperature. They must also adjust the said proportion depending on the desired properties of the metals.
An atmosphere dominated by nitrogen will not generate any noteworthy reactions to the non-ferrous metals. The protective gas then eliminates oxidising gases from the process chamber. And as the hydrogen content of the furnace temperature increases, the surface oxidation of the involved metals decreases significantly.
But to make this heat treatment process successful, the furnace used for this process should be clean and free from moisture. The non-ferrous metals must also be dry and clean.
Main Advantages of Bright Annealing
What is great about bright annealing is it can boost the corrosion resistance of non-ferrous metals by a huge percentage. The corrosion resistance of these metals can be improved as the process can eliminate intergranular carbide precipitation. This process can also improve their surface finish as well as reduce their buffing costs. The original metal lustre of non-ferrous metals and other metal types is even preserved and maintained through bright annealing. Bright annealing should be conducted by experts so that non-ferrous metals can boast these advantages. To know more about this process, you can call us at Alpha Detroit Heat Treatment.
Most metal products being utilised by industries today must undergo heat treatment first. Heat treatment is a process wherein metal workpieces are subjected to heat without letting them reach their molten state. They are then cooled in a controlled way, ensuring that they attain the mechanical properties required by a specific industry.
With heat treatment, metal workpieces are expected to become more durable, tougher, and stronger. They can likewise attain improved wear resistance, better flexibility, and enhanced weldability. Their overall service life is also expected to increase significantly.
But heat-treated metals may still boast some defects because of a wide variety of reasons. Here are some most common defects of heat-treated metals you should know about.
Low Hardness and Strength
Metals, especially steel, need martensitic formation to achieve high hardness and strength. Without achieving these properties, it would be difficult for industries to acquire their needed products. The absence of better hardness and strength is due to improper austenitising temperature. It can likewise be caused by insufficient soaking duration, slow cooling rate, the existence of retained austenite, and low hardness during surface hardening treatment.
Soft Spots
After quenching from austenitising temperature, metals are expected to attain an even hardness across their surfaces. But if their hardness becomes uneven from point to point, they may have acquired some soft spots. Soft spots in metals may be caused by quenching media issues. Once water generates a vapour blanket stage, it will ultimately reduce the critical cooling rate of specific workpiece areas. Soft spots can also happen due to high quenching media temperature, localised decarburisation, uneven heating, and improper cleaning of metal parts.
Quench Cracks
Quenching is essential to effectively cool metal workpieces so they can be subjected to martensitic transformation. Normally, this heat treatment phase is accompanied by various tensile and compressive stresses. But in some cases, these stresses may become severe, resulting in cracks during heat treatment. These cracks, also known as quench cracks, make metal workpieces useless and unusable.
Oxidation and Decarburisation
Oxidation and decarburisation are two more potential reasons heat-treated metals can become defective. Oxidation may happen once metals are exposed to carbon dioxide, air, and water vapours during specific phases of heat treatment. Without immediate mitigation, metals may become porous, resulting in material degradation and loss of properties. Decarburisation, alternatively, may occur when some metals are exposed to heat above 650 degrees Celsius. This issue may then result in loss of fatigue strength.
Distortion and Warping
These defects of heat-treated metals are normally irreversible, which makes them two of the costliest mistakes that heat treatment companies may commit. Distortion happens when metal workpieces acquire a symmetrical change in shape or size, while warping occurs if the changes are asymmetrical. Metals may undergo two types of distortion: size and shape distortions. Size distortion occurs during the expansion and contraction stages of heat treatment, while shape distortion happens due to the bending and twisting of metals. Some elements that must be checked to prevent these issues are initial composition, design, and machining processes.
To ensure that your heat-treated metals will not acquire any defects, you can work with us at Alpha Detroit Heat Treatment. Contact us today!