Heat Treatment Furnaces
Heat Treatment is the controlled heating and cooling of metals to intentionally alter their physical, mechanical and sometimes chemical properties without changing the product shape. The technology is often linked to increasing the strength of the material, but it can also be used to alter certain manufacturing objectives such as improve machining, improve formability, restore ductility after a cold working operation. Thus, it is a very enabling manufacturing process that can not only help other manufacturing processes but can also improve product performance by increasing strength or other desirable characteristics.
Silcarb designs and manufactures thermal processing furnaces that incorporate most of the heat treatment processes (annealing, quenching, tempering, etc). They are known for their heating uniformity, cost-effectiveness, and low maintenance needs. Silcarb heat treatment furnaces are available in a wide variety of configurations and temperature ranges, which are customizable. The furnaces manufactured are simple, rugged and conventional in design. The furnaces are very resourceful and trouble-free. The units are built with a heavy gauge steel shell and the heating elements used to have low watt density along with lightweight ceramic insulation making these furnaces suitable for any laboratory or industrial application.
Furnaces are available in many configurations that include single zone or multiple zones heated chambers and temperature ranges up to 1010°C, 1204°C, 1538°C, or 1700°C. Options include pneumatic door openers, viewports, the sealed chamber with ports for atmosphere control, heated doors, quench tanks, automation, standard controls, and PLC controls. These are only some of the features offered by silcarb. silcarb also manufactures furnaces for different heat treatment processes.
Types of Heat Treatment furnaces manufactured by silcarb:
- Ageing Furnaces
- Quenching Furnaces (Drop bottom type)
- Solutionising Furnaces
- Gas Carburizing Furnaces
- Tempering Furnaces
- Annealing Furnaces
Aging is a process used for a range of metals to alter the properties of the material being treated, sometimes to increase strength and hardness, and other times to improve formability in the case of over-aging. Because aging is generally conducted at lower temperatures, temperature uniformity and precise heating and cooling rates can be critical. Thus, the name Aging Furnaces. The aging process is used after other heat-treating processes to set the properties of the alloy which results in increased strength and durability.
This equipment is mainly used for the final hardening treatment to finished products, which is applicable to various aluminum sections. It can be divided into single-door, double-door, skip manual and maneuvering types in terms of its structure, and fuel oil, fuel gas as well as electric heating types in terms of heating mode, it is mainly used to the aging procedures for aluminum sections at the maximum temperature of 260℃. Silcarb aging furnaces have high-temperature uniformity both in the fuel-fired as well as the electric systems. Suitably designed hydraulic or electromechanical doors are designed for an airtight function of the aging ovens.
All electricals are touch-controlled with a complete SCADA automation system with an HMI touch display to program the entire sequence of operations. Silcarb manufactures small ovens of 1mx1mx1m up to large systems which are above 20 square meters. Air circulation systems are set up to achieve temperature uniformity all over the chamber.
Quenching furnaces (Drop bottom type furnaces)
The Drop Bottom Furnace is an inverted type with charge lifting and lowering facility to accommodate the high-speed quenching including de-clamping, door opening, and quenching. The Drop Bottom Furnace can be a standalone type with charge carrier loader and quenching tank moving on the floor or floor mounted with charge carrier loader and quench tank/s sliding in a pit. As the requirement is very fast quenching it is fully automated using PLC and SCADA. These furnaces can also be used for a continuous aging cycle ranging from 16 – 24 hrs time. Various quench media such as water, glycol or other polymer oils as per process requirements are used. Area of application is generally used in aeronautical industries for solutionizing and aging of structural parts, also in forging industries of aluminum alloy forgings. In some cases where silcarb encounters a no standard shaped part which needs to go through the entire T6 processes of solutinising and aging the suggested furnace the drop bottom or drop quench furnace.
Silcarb has a number of drop quench furnace installation all over India. The quench time is as low as 11 seconds for baskets sizes up to 3000mm in length. Silcarb uses high-grade steel baskets which as reinforced to give a very long life without any warpages even with continuous usage. The entire system is hydraulically operated with no use of any electro-mechanic systems making the equipment very safe to use as well as keeping the quench time less than 11 seconds from the “door open” moment. The circulating fan is designed with special water-cooled bearings with aluminum die-cast heat-sinks which makes the pre-balanced air circulating fan very efficient and long-lasting. Refractory lining is designed to be lightweight and efficient. Silcarb uses its highly efficient in house manufactured silicon carbide heating elements as the main heat source.
The clamp doors are designed with three equidistant hydraulic cylinders that enforce proper clamping of the bottom door with no air leakages The door draw out cylinders are of high-speed actuation which reduces the time of quench. The Silcarb drop quench(bottom drop) furnace has the option of having the water tank above the ground (where there is excess residual sand in the castings) or below the ground. In cases where the quench tank has to be moved above the ground, silcarb has a high capacity hydraulic system that would move the tank over prefixed rails on the shop floor. The quench tank is usually supplied with electric heaters and high velocity specially designed agitators.
The purpose of the solutionize procedure is to simply put into solution the maximum number of alloying elements that are present in that alloy. This can be likened to making a saturated solution of salt and water. A saturated solution of saltwater simply means that there is an excessive amount of salt present in the water. The way to take the excess salt into water is to simply heat the water. The salt will now go into a solution. If the saltwater is now allowed to cool down from the heated temperature, however, the salt will precipitate out of the solution. To keep the salt in its solute form, you could freeze it (the principle of aluminum solutionizing treatment).
The problem with aluminum solutionizing is that the required solutionize for temperature is very close to the liquidus temperature, where grain boundary melting can initially begin. For this reason, temperature uniformity within the furnace process chamber is critical to the procedure. If one does not have good temperature uniformity, only localized solutionizing will occur. Further, if the part that is being treated has varying cross-sectional thicknesses, one will need to ensure that the part has uniform solutionize temperature throughout its cross-section without causing grain-boundary melting.
In order to achieve temperature uniformity, it is necessary to ensure that the air within the furnace process chamber is not static but has movement. Therefore, the furnace must have an air-circulation fan or systems of fans to ensure uniform heated air movement.
Silcarb manufactures a whole range of solutinising furnaces
Gas carburizing furnaces
Gas Carburising Process is a surface chemistry process, which improves the case depth hardness of a component by diffusing carbon into the surface layer to improve wear and fatigue resistance. The workpieces are pre-heated and then held for a period at an elevated temperature in the austenitic region of the specific alloy, typically between 820 and 940°C. During the thermal cycle, the components are subject to an enriched carbon atmosphere such that nascent species of carbon can diffuse into the surface layers of the component. The rate of diffusion is dependent on the alloy and carbon potential of the atmosphere. Care must be taken to ensure that only enough carbon is available in the atmosphere at any one time to satisfy the take-up rate of the alloy to accept the carbon atoms. Once the heating and carbon diffusion part of the process is complete it is necessary to rapidly quench the components to a defined alloy recipe. The recipe will specify the quench method, the quenchant temperature and time. Gas carburizing and other surface chemistry treatments can be carried out in batch or continuous furnaces dependent on the parts under treatment and the user requirements. Silcarb manufactures a whole range of gas carburizing furnaces.
A tempering furnace is a type of industrial oven designed to heat treat a ferrous metal product and increase its toughness. It is the process of accessing the highest possible intersection of strength and elasticity of a ferrous, or iron-based, metal product by heat-treating it to a limited degree, typically after the quenching process. Silcarb tempering furnace uses home manufactured silicon carbide heating elements lined with electrical wires or coils to uniformly heat a sample chamber to different heating ranges depending upon the desired material characteristics of the product. An iron-based metal is heated in a tempering furnace to between 300 – 750°C (572 – 1382°F), to encourage phase transitions within the martensite structures and reduce the hardness of the material while improving its ductility. It is crucial that the tempering furnace can accurately maintain temperature levels and temperature uniformity throughout the sample chamber to negate the likelihood of metal warping or fracture. Silcarb manufactures a whole range of tempering furnaces
Annealing involves heating steel to a specified temperature and then cooling at a very slow and controlled rate. Annealing is commonly associated with the manufacture of steel, to relieve internal stresses that may lead to failure in service and to produce a more uniform, or homogeneous, internal structure. The stages of annealing furnaces include – 1. Heating to the required temperature. 2. Holding (“Soaking”) at a constant temperature. 3. Cooling.
The time at the high temperature (soaking time) is long enough to allow the desired transformation to occur. Cooling is done slowly to avoid warping/cracking due to the thermal gradients and thermoelastic stresses within the metal piece. This process is also commonly used with various metals, glass, and other materials to make them less brittle and more workable.
Silcarb manufactures a whole range of Annealing furnaces
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