High Carbon Spring Quenched and Tempered Steel Strip
High carbon spring quenched and tempered steel strip is a material used in a wide range of engineering components. These include automobile clutches, clock springs and hand tools.
The process of hardening and tempering is a thermal treatment that strengthens cold rolled steel strip by heating it above its critical transformation temperature, then cooling it rapidly. The process is essential for achieving the desired mechanical properties, such as hardness and tensile strength.
Hardening & Tempering
High Carbon Spring Quenched and Tempered Steel Strip is used in automotive clutches, clock springs, masonary tools, gang saw blades and hand tools. This product is a highly engineered solution for specific end-use applications. The hardened and tempered steel strip is produced on continuous heat-treating lines. Each line contains 2 furnaces. The first one, the hardening furnace, heats the steel to temperatures from which it rapidly cools. This makes the steel very hard but also very brittle, therefore tempering is required to develop the ductility and shock resistance properties that the industry requires.
The hardening process can be conducted either in an open furnace or under a protective atmosphere (gas, vacuum or molten salt) to prevent scaling and decarburisation. The choice of treatment depends on the steel analysis and component geometry as well as the desired mechanical properties. Every steel grade has a limiting section size above which full hardening cannot satisfactorily be achieved. It is important to understand these limitations and design accordingly.
During tempering the microstructure of the steel changes from stable martensite to a mixture of ferrite and cementite, which are much tougher than martensite. It is possible to achieve a very high degree of toughness and shock resistance by controlling the tempering temperature. The time the steel is held at the tempering temperature is also important, as it can significantly affect the final hardness.
Annealing
The annealing process softens materials that have become hard and brittle due to previous manufacturing High carbon spring steel coil processes such as heating/quenching, cold working, or machining. It also increases the ductility and malleability of the metal, making it easier to work with during subsequent processing steps.
The temperature of the annealing process may vary depending on the grade of steel and its desired properties. Metallurgical experts and industry professionals are able to provide valuable insight into the optimal heat treatment parameters for different grades of steel. It is important to follow the recommendations of these experts and professionals in order to achieve the best results.
Once the strip has been tempered, it is ready for use in a variety of industrial applications. This grade of steel is ideal for flat springs, dowel pins, automotive clutch plates and chain parts, horticulture sickles, and many other types of cutting blades. It offers excellent ductility and shock resistance while maintaining high levels of toughness.
Tempered High Carbon Spring Quenched and tempered Steel Strip combines ease of fabrication with good strength and surface finish. It is used in a wide range of commercial and industrial products including valve plates, flapper valves, air compressor units, horn diaphragms and brackets, automotive clutches, and clock springs. Its fine tempered Martensite microstructure provides excellent surface finish and superior spring and cutting properties.
Quenching
Quenching is the process of cooling a hardened steel strip rapidly to set the crystalline structure. This makes the steel much stronger and harder. However, this makes the steel very brittle and requires tempering to restore some of its flexibility and ductility.
The steel is heated above its critical transformation temperature (which varies by grade), then quenched to quickly cool it. This can be done by immersing the steel in water, oil, forced air, molten salt or even pressurised gas such as nitrogen. The choice of the quenching medium depends on the application and the workpiece geometry, the heat treatment furnace used and the steel analysis.
A fast cooling rate allows the crystalline structures of martensite and bainite to form in the austenite grain. This reduces the risk of cracking during further processing and increases the strength of the final product. However, if the steel is not tempered properly, it will become too hard and brittle for its intended use.
Tempering is the process of heating the brittle quenched steel to a lower temperature, which decreases the hardness and brittleness and increases the toughness and ductility. This also relieves internal stresses in the steel and allows it to return to its original shape. This thermal treatment is often repeated to achieve the desired mechanical properties in the finished product.
Finishing
Upon quenching the steel becomes very hard – but also very brittle – and requires further thermal treatment Hardened & Tempered Steel Strip Supplier (tempering) to give it some of the ductility which its end use industries require. This is carried out on continuous production lines at voestalpine Precision Strip WI in Pleasant Priarie, USA in state-of-the-art, continuous tempering furnaces from EBNER of Austria.
The resulting product is flat cold rolled medium high carbon spring martensite steel, blue-black in colour, with the Rockwell hardness of C44/47. This material can be used in applications similar to that of clock spring steel such as automobile clutches, masonary and agricultral tools, gang saw blades, doctor blades etc.
It has the added advantage that it is less sensitive to distortion – in other words it can be bent to a much narrower shape without losing its ability to return to its original form when unloaded. This makes it an ideal material for springs and band saw blades.
Tempered steel has excellent mechanical properties and can be supplied in a range of options including slit edge, rounded or dressed edges, and with surface finish options of grey, bright polished or blued. It is available in a wide variety of sizes, chemistries, tempers and finishes to meet most customer requirements. The production process allows for tight thickness & width tolerances and shear & flatness control.
