Quenched and Tempered Steel Plate
QUENCHED AND TEMPERED STEEL PLATES
Temperature control in heat treatment has significant impact on the microstructure and mechanical properties of materials. The heating temperature, cooling rate and the type of fluid used are critical to the formation of the final structure.
When the cooling rate becomes too fast to allow complete hardening, only surface martensite is formed. This results in low ductility and strength.
Hardening
The process of quenching and tempering steel is used to increase both hardness and strength. It involves heating the material to a high temperature and rapidly cooling it. This causes the formation of a harder, stronger structure known as martensite. It also relieves internal stresses. The resulting steel is much more durable and has increased resistance to impact and abrasion.
While the quenching process can be done with water, oil, air, or even inert gases like nitrogen and helium, it is more commonly done in controlled environments because of the extreme temperatures required to achieve full hardening. The cooling must be rapid enough to form the desired martensite, but slow enough to prevent distortion in the component. If the cooling rate becomes too fast, the component will only become hard in the surface region.
This type of heat treating is often done for components that require both exceptional strength and toughness such as:
Ductility
Ductility is a property that describes how much a material can stretch or elongate before it fails. Metals are ductile because of metallic bonds, which allow electrons from different atoms to flow freely Quenched and tempered steel plate between them. This allows them to be stretched without breaking, whereas other materials would shatter when subjected to the same stress.
To determine a material’s ductility, it is tested in a tensile test. The sample is flat or round and resembles something like a dog bone or a dumbbell, with grip sections on each end and the smaller gauge section in the middle. It is held tight between upper and lower jaws, which apply a tensile load. A stress-strain curve can then be plotted as the specimen is stretched to failure. The ductility is the percentage of change in the gauge section length compared to its original length.
The tempering process that follows quenching adds to the ductility of the steel. This is done by heating the steel plate to a lower temperature range and cooling it in still air. This decreases the hardness of the martensite and makes the metal less brittle, so that it is more workable. Leeco stocks a variety of grades of quenched and tempered steel plate that is ideal for military, mining, construction and earthmoving applications, such as dump truck wear liners, construction buckets, chutes and more. Contact a Clifton specialist for more information on how this steel can help your application.
Strength
Quenching and tempering are procedures that reinforce materials like steel and other iron base alloys. Both processes increase the strength of these materials by heating them while instantaneously cooling in water, oil, forced air, or gases such as nitrogen. Quenching and tempering strengthen the steel plate to meet demanding abrasion and impact resistance specifications.
In unalloyed steels with a large cross-section, the cooling rate required to fully harden the material cannot be achieved across its entire surface due to high thermal stresses in the workpiece. This is known as quench distortion and can cause cracking in the steel.
The temperature at which the unstable martensite decomposes into ferrite and cementite is called the critical point. The cooling process during quenching lowers this critical point and increases the material’s strength and ductility. This type of steel is used for heavy equipment, mining and construction applications, where high abrasion resistance is necessary.
Leeco keeps numerous grades of quenched and tempered steel plate in stock to ensure that we can deliver this heavy-duty product for your project. These grades are often used in machinery, earthmoving equipment and dump truck wear liners. If you’re looking for a steel plate that can stand up to tough, impact working conditions talk to one of our specialists today about the benefits of quenching and tempering your plate.
Durability
The combination of the quenching and tempering Tinplate steel plate manufacturer processes creates a material that is tougher and more resistant to impact and abrasion than untreated steel. It is ideal for machinery and structures that need high yield strength and abrasion resistance, such as mining, quarrying, earth moving and construction.
The key to this process is the creation of a stable microstructure that does not crack under stress. In order to achieve this, the steel must have a high carbon content (between 0.3% and 0.5%). This allows the martensite in the initial pearlite microstructure to form a strong lattice distortion during quenching, which greatly increases its strength and toughness.
However, it is also necessary to perform a tempering process immediately after quenching to stabilise any retained austenite structures that do not transform into martensite. This can help to prevent cracking in the workpiece, which can occur due to insufficient tempering, overly high hardening temperatures or improper cooling methods.
Tempering is the process of reducing the hardness of the quenched and tempered steel plate by heating it for a set period of time at a temperature that is below the critical point, then cooling it in still air. The temperature, the duration and the type of tempering substance used will determine how much hardness is removed. The resulting material is a stronger, tougher and more ductile metal that is also weldable.