Quenched and Tempered Steel Plate
Quenched and tempered plate, or Q&T, is ideal for use in machinery that needs to hold up to severe impact and abrasion. Leeco Steel stocks a number of grades in this category, including the ASTM A514.
The Q&T process involves heating a steel material to an extreme temperature and rapidly cooling it with water (quenching) followed by reheating the steel to a below-critical temperature and cooling it at normal air temperatures (tempering). This produces strength and toughness.
Strength
Quenching and tempering alters the grain structure of steel plate, resulting in increased hardness and toughness. These characteristics make quenched and tempered steel plate ideal for projects that require a high level of durability, such as construction equipment (dump trucks, trailers, cranes) and mining equipment.
In metallurgy, strength is defined as the resistance to permanent deformation and tearing. There are several factors that contribute to the strength of metals, including yield strength (the amount of stress at which deformation becomes permanent), tensile strength (the maximum tearing force), shear strength (resistance to transverse, or cutting forces) and compressive strength (resistance to bending).
The high temperature required for quenching can cause significant thermal stresses in the plate, causing distortion or cracking. For this reason, it is important to use a cooling element that will maintain constant temperatures. A variety of different cooling elements can be used, including mineral and vegetable oils, water, and inert gases like nitrogen and helium.
In addition to quenching, some grades of steel undergo a secondary heat treatment known as precipitation hardening. This process involves two periods of reheating and rapidly cooling steel plate, as well as the alteration of the steel’s grain structure to increase strength and toughness. Grades stocked by Leeco that are precipitation hardened, such as ASTM A710, have higher tensile and yield strengths than untreated grades, which allows them to withstand the stresses of harsh environments.
Durability
Quenched and tempered steel plate has the strength to withstand harsh Quenched and tempered steel plate conditions like extreme impact or abrasion. This is because the material is heat-treated, a process that intensely heats and rapidly cools the metal to alter its physical properties. Q&T plate is commonly used in construction and manufacturing equipment, such as dump bodies, crane booms, hauling and lifting equipment and truck and trailer frames.
The first heat treatment step, known as quenching, involves bringing the steel to its critical temperature then immediately cooling it by soaking it in water or oil. The second heat treatment process, called tempering, involves heating the quenched metal to a temperature below its critical point and then slowly cooling it with still air (also called forced air). The key difference between these processes is that the tempering phase slows the rate of hardening in the steel to help maintain toughness and ductility.
To achieve the desired level of hardness, the steel needs to have a high carbon content. For this reason, unalloyed steel is not suitable for quenching and tempering. Alloyed grades, on the other hand, can be made to achieve a higher hardness by adding more elements like manganese, nickel and molybdenum. These higher levels of hardness also provide greater corrosion resistance. For example, chromium-alloyed steels are resistant to oxidation and rust.
Abrasion Resistance
The harsh environments where construction and manufacturing equipment operate require materials that can withstand severe impact and abrasion. To meet these requirements, project engineers often choose quenched and tempered steel plates, which are heat-treated to alter the material’s physical properties. Leeco stocks many grades of Q&T plate, including A710 and AR450F. These grades are characterized by their high toughness and abrasion resistance.
In order to produce these qualities, the steel must undergo a two-stage heat treatment process that includes quenching and tempering. Quenching involves heating the steel to a high temperature and then immediately cooling it with water. This process causes the crystal structures within the steel to re-form and increases its hardness.
Tempering is a follow-up procedure that lowers the hardness of the steel and enhances its ductility. It accomplishes this by reheating the steel to below its critical point and then cooling it rapidly in forced air (primarily composed of nitrogen).
While the advantages of quenching and tempering are clear, these processes don’t always achieve the desired results. Specialized metal treatment experts know how to tweak these processes for different alloys and applications. When performed correctly, this combination of procedures produces the toughness and abrasion resistance necessary for most industrial applications.
Heat Resistance
Using a process that heats and cools the metal, quenching creates a hard martensite microstructure. This distorted structure inhibits the movement of dislocations, which makes the metal extremely hard but also less ductile than pure carbon steel. When the alloy is tempered, however, the lattice distortion diminishes and a more ductile martensite forms. This allows the steel to bend or deform rather than breaking, increasing its strength and allowing it to handle high impacts and loads.
The combination of increased abrasion resistance and yield strength makes quenched and tempered plate ideal for projects that require durable material, including construction equipment, crane booms, dump trucks, trailer frames and mining equipment. Leeco stocks a variety of grades Tinplate Sheet Manufacturer and thicknesses of quenched and tempered steel plates, but one of the most popular is ASTM A514. This grade features an enhanced chemical composition that gives it greater weldability and machinability compared to non-heat treated alloys.
Contact a Kloeckner Steel specialist to learn more about our inventory of quenched and tempered steel plates. Our team of experts will help you select the right type and size for your application, and we offer numerous metal fabrication services like laser and plasma cutting, leveling, shearing and metal forming in-house.
