Quench and Tempered Steel
Strong and durable, quench and tempered steel can be used in applications such as mining, drilling, earthmoving, and construction. Tempering increases ductility, which makes the metal resistant to breakage.
The heat treating process begins with austentizing, which involves heating the forging blanks to a critical temperature for a set amount of time. Then, the steel is rapidly quenched.
Quenching
If you want to cut metal with a sharp, hard edge, the steel must be hardened. Quenching is the process of heating the steel to its critical temperature (austenitic), and then rapidly cooling it. This results in the formation of martensite, which gives the steel its hardness. However, the hardness created by quenching also makes the steel brittle.
The process of quenching can be performed in a variety of ways: water, oil, air, and even inert gases such as nitrogen. The method chosen depends on the type of steel and the desired properties of the finished product.
Care must be taken to ensure that the heat treatment is done properly. Any deviation from the recommended temperatures may result in weak or brittle metal. The cooling rate of the metal is also an important factor. Faster cooling rates result in higher levels of hardness, while slower rates produce softer materials.
Once the steel is hardened, it must be tempered to reduce its brittleness and increase its toughness. To do this, the metal is reheated to a lower temperature for a short time and then allowed to cool. This tempering process is often repeated several times, as different temperatures are required to achieve specific mechanical properties. In addition, tempering can help to eliminate stresses that could crack components after final machining and assembly.
Tempering
The tempering process is the reheating and slow cooling of the metal, and it allows us to balance the hardness and ductility characteristics brought out by quenching. The temperature and duration of the tempering process quench and tempered steel are critical to achieving optimal properties and should always be performed immediately after quenching to prevent damage and distortion.
Tempering is also used to relieve internal stress, improve toughness and dimensional stability, and to achieve the desired mechanical properties for specific applications. This is achieved by transforming the hard and brittle martensite into more ductile forms such as bainite, tempered martensite or ferrite.
In tempering, a fascinating color spectrum unveils the material’s transformation from a harsh and brittle state to one that has a certain degree of resilience and toughness. This is accomplished through a combination of heating and cooling, with the specific temperature, heat duration and cooling rate chosen to achieve optimum results.
Tempering is often applied to tool steels to improve their ability to retain a sharp cutting edge, and it is also commonly used in construction, mining and earthmoving industries for products such as:
Mechanical Properties
In metallurgy, strength and toughness are two important properties of steel. Strength is the resistance to permanent deformation and tearing while toughness refers to the ability of the material to bend before breaking. Quenching and tempering increase both of these qualities.
The hardening process requires precise control to ensure the proper microstructure and mechanical properties are achieved. The exact temperature, cooling methods and speed can all have a significant effect on the finished product. For example, a fast cool down may result in a more austenitic grain structure while a slower, lower-temperature cooling can produce a bainite microstructure.
After the quenching process, the steel is tempered to reduce its hardness and improve its toughness. This involves heating the steel, holding it at a low temperature for a period of time and then cooling it again. The tempering temperature affects how the dislocation atoms move in the steel, which alters the morphology of the tempered martensite and the overall toughness.
Depending on the application, different tempering temperatures are used to achieve a balance between hardness and toughness. For example, high-performance engine crankshafts must be extremely hard but also have excellent toughness to withstand the extreme motor forces. The tempered martensite in these steels has a strong lattice distortion, which blocks the flow of dislocations and greatly increases the ductility of the steel.
Applications
After quenching, steel is tempered to reduce its hardness and improve its toughness. The process involves reheating the steel to specific temperatures that vary depending on the intended outcome of the heat treatment. Tempering helps to re-distribute carbon atoms from the Tinplate steel coils supplier tetragonal martensite back into the austenite structure and relieves internal stresses caused by the quenching process.
Tempering also re-sizes the microstructure of the steel. It makes it possible to achieve a more uniform internal crystal grain size which can result in improved workability. Tempering can also help to control the formation of pearlite. This can improve the cutting ability of the steel and is important for machinability.
The final results of tempering are a reduction in the brittleness of the steel, improved toughness and better resistance to fracture and fatigue. Enhanced fatigue performance can be particularly beneficial in applications such as shafts or axles that are subject to frequent cycling of loads where failure would have a catastrophic effect.
Heat treated tubulars with high tensile strength are used in oil drilling, as well as being an increasingly common choice for automotive components where a combination of high strength and light weight is needed. Other industrial applications include valve bodies, gears and fittings. The advantages of quenched and tempered steel are numerous and it is an important technology for manufacturers who are looking to maximize the use of their resources.