What is differential quenching?
Differential hardening (also called differential quenching, selective quenching, selective hardening, or local hardening) is most commonly used in bladesmithing to increase the toughness of a blade while keeping very high hardness and strength at the edge.
What is a differential hardened blade?
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What is difference between hardening and tempering?
Hardening or quenching is the process of increasing the hardness of a metal. Tempering is the process of heating a substance to a temperature below its critical range, holding and then cooling.
What is the difference between heat treating and tempering?
Both heat treatments are used for treating steel, although annealing creates a softer steel that is easier to work while tempering produces a less brittle version that is widely used in building and industrial applications.
What is annealing vs tempering?
Annealing involves heating steel to a specified temperature and then cooling at a very slow and controlled rate, whereas tempering involves heating the metal to a precise temperature below the critical point, and is often done in air, vacuum or inert atmospheres.
Why do you need tempering after hardening?
Tempering is usually performed after hardening, to reduce some of the excess hardness, and is done by heating the metal to some temperature below the critical point for a certain period of time, then allowing it to cool in still air.
What are the three types of tempering?
4. Classification of Tempering:Low Temperature Tempering (1-2 Hours at a Temperature up to 250°C): Low temperature tempering is done to reduce brittleness without losing much hardness. ... Medium Temperature Tempering (350 C to 500°C): ... High Temperature Tempering (500-650°C):
Why annealing is done?
The main advantages of annealing are in how the process improves the workability of a material, increasing toughness, reducing hardness and increasing the ductility and machinability of a metal.
What is the difference between annealing and normalizing?
The main difference between annealing and normalizing is that annealing allows the material to cool at a controlled rate in a furnace. Normalizing allows the material to cool by placing it in a room temperature environment and exposing it to the air in that environment.
What are the three stages of heat treatment?
Stages of Heat TreatmentThe Heating Stage.The Soaking Stage.The Cooling Stage.
Which heat treatment gives highest hardness?
Water cooling gives a high cooling rate in the temperature range of martensite formation which the reason for the highest hardness.
What is the difference between annealing and quenching?
The main purpose of annealing is to remove the hardness of metal alloys and increase ductility. After quenching, metal tends to become brittle, and that can increase the risk of breakage. Annealing balances the properties of metal alloys to maximize strength and durability for a variety of applications.
What is heat treatment?
Heat treatment is a heating and then cooling process using predefined methods to achieve desired mechanical properties like hardness , ductility, toughness, strength, etc. It is the combination of thermal, industrial, and metalworking processes to alter the mechanical properties and chemical properties of metals.
What is differential hardening?
Differential hardening is kind of a hardening process in which different area of the metal piece gets a different heat-treatment process. This is a very popular hardening process for high-end cutting tools.
How does heat treatment help metals?
Heat treatment assist in improving the ductility of metal in the annealing process. Heat treatment helps in hardening metals. Case hardening helps in hardening only the outer surface of the metal piece keeping the rest of the portion soft and ductile. Machinability of metals gets improved.
How is annealing done?
Annealing is done by heating the metals at the above critical temperature , hold them there for some time and then cool it at a very slow rate in the furnace itself. Annealing is usually done on ferrous and non-ferrous metals to reduce hardness after the cold working process.
What is the process of increasing the hardness of a metal?
Curborization. In carburization, the hardness of the metal piece is increased by increasing the carbon content. The metal piece is heated below the melting point with high carbon materials such as charcoal. The heated metal piece then absorbs carbons to make it more hard and brittle.
What is case hardening?
Case hardening or surface hardening is a hardening heat-treatment process. In the case of hardening, the complete metal piece is heated. But in the case of case hardening, only the outer surface is heat-treated to make it hardened. The inner metal is still soft and ductile.
What is process annealing?
Process annealing is done when metal is heated below the critical temperature, keep it for a suitable time, and then cool it slowly. This process is suitable for low carbon steel like sheet metal and wires. No phase transformation occurs during process annealing, and it’s considerably cheaper than full annealing.
What is the process of heating something to alter it?
Process of heating something to alter it. Heat treating furnace at 1,800 °F (980 °C) Heat treating (or heat treatment) is a group of industrial, thermal and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are also used in the ...
Why is heat treatment called an arrest?
This temperature is referred to as an "arrest" because at the A temperature the metal experiences a period of hysteresis.
Why are nonferrous alloys annealed?
Most non-ferrous alloys that are heat-treatable are also annealed to relieve the hardness of cold working. These may be slowly cooled to allow full precipitation of the constituents and produce a refined microstructure. Ferrous alloys are usually either " full annealed" or " process annealed.".
What is a semi continuous batch furnace?
These upgraded furnaces are a very commonly used piece of equipment for heat-treating.
What is a bell furnace?
Bell-type furnace. Bell furnaces have removable covers called bells, which are lowered over the load and hearth by crane. An inner bell is placed over the hearth and sealed to supply a protective atmosphere. An outer bell is lowered to provide the heat supply.
What is steel heated up?
Let’s start with the basics. In its simplest form, steel is heated up hot, quenched, and tempered. This provides the desired properties at the end which include high hardness in combination with sufficient toughness. There is not enough space here to fully explain the entire process.
Does the knifemaker have heat treatment?
That doesn’t mean that the knifemaker doesn’t have a very good heat treatment, but end users are less apt to notice a heat treatment that is a little bit better than another, as opposed to a knife with superior design and edge geometry.
Is heat treatment good for knives?
The Legend of Heat Treatment. There is some debate about knives that have steel with a “good heat treatment” vs those that have a bad or sub-par heat treatment. Some knifemakers have a near legendary reputation for their excellent heat treatments.
Can knifemakers use heat?
Many knifemakers perform a good heat treatment. Using a well controlled furnace for austenitizing, quenching in a good medium, and tempering correctly can lead to a good heat treatment in most cases. Especially when following recommendations in the steel datasheet which provides recommended temperature ranges.
Overview
Techniques
Complex heat treating schedules, or "cycles", are often devised by metallurgists to optimize an alloy's mechanical properties. In the aerospace industry, a superalloy may undergo five or more different heat treating operations to develop the desired properties. This can lead to quality problems depending on the accuracy of the furnace's temperature controls and timer. These operation…
Physical processes
Metallic materials consist of a microstructure of small crystals called "grains" or crystallites. The nature of the grains (i.e. grain size and composition) is one of the most effective factors that can determine the overall mechanical behavior of the metal. Heat treatment provides an efficient way to manipulate the properties of the metal by controlling the rate of diffusion and the rate of cooling within th…
Effects of composition
The specific composition of an alloy system will usually have a great effect on the results of heat treating. If the percentage of each constituent is just right, the alloy will form a single, continuous microstructure upon cooling. Such a mixture is said to be eutectoid. However, If the percentage of the solutes varies from the eutectoid mixture, two or more different microstructures will usually form sim…
Effects of time and temperature
Proper heat treating requires precise control over temperature, time held at a certain temperature and cooling rate.
With the exception of stress-relieving, tempering, and aging, most heat treatments begin by heating an alloy beyond a certain transformation, or arrest (A), temperature. This temperature is referred to as an "arrest" because at the A temperature the metal experiences a period of hystere…
Specification of heat treatment
Usually the end condition is specified instead of the process used in heat treatment.
Case hardening is specified by hardness and case depth. The case depth can be specified in two ways: total case depth or effective case depth. The total case depth is the true depth of the case. For most alloys, the effective case depth i…
Furnace types
Furnaces used for heat treatment can be split into two broad categories: batch furnaces and continuous furnaces. Batch furnaces are usually manually loaded and unloaded, whereas continuous furnaces have an automatic conveying system to provide a constant load into the furnace chamber.
Batch systems usually consist of an insulated chamber with a steel shell, a hea…
See also
• Carbon steel
• Carbonizing
• Diffusion hardening
• Induction hardening
• Retrogression heat treatment