High Carbon Spring Quenched and Tempered Steel Strip
High carbon spring quenched and tempered steel strip is produced by continuous heating furnace and oil quenching. It can be supplied with different options such as slit, rounded or dressed edge.
The hardening treatment involves heating to a critical transformation temperature for the given steel analysis and component geometry followed by rapidly cooling through quenching. This produces the optimum combination of hardness, strength and toughness.
Characteristics
The high carbon content of the HSQT strip results in it having good yield strength and high tensile strength. High carbon spring quenched and tempered steel strip It is however, brittle in its hardened and tempered condition. This is because the microstructure is dominated by a mixture of acicular and lenticular martensite as well as ferrite. It is therefore important to temper the material adequately to balance its brittleness with its ability to deform elastically.
Tempering involves a three-stage process during which unstable martensite transforms into ferrite and finally stable cementite. This is achieved by holding the steel at temperatures above its martensite finish temperature (Mf) for varying lengths of time. The Mf temperature varies with the carbon content and alloying contents of the steel as does the amount of retained austenite.
The tempering treatment can be carried out in a wide range of ways, depending on the requirements of the component being made. Typical options include open furnace treatments in air or combustion products, protective gaseous atmospheres, molten salt quenching and vacuum quenching. Open furnace treatments can produce scaling and decarburisation on the surface of the work-piece. This can be minimised by careful component design, selecting suitable steels and appropriate heat treatment procedures. In some cases, particularly with large components it may be necessary to use a martempering technique to reduce the stresses caused by rapid quenching.
Applications
Hardened and Tempered Spring Steel strip is used in a wide range of special industrial applications. It has excellent spring and toughness properties due to its fine tempered Martensite microstructure. It also has high tensile strength and good workability characteristics such as ductility and shock resistance. It can be cold rolled, cold formed and machined with good ease. Its precision blanking ability enables the reduction of post heat treatment distortion and increases productivity.
The optimum combination of hardness; strength and toughness is developed throughout the strip cross section by means of a controlled heating to the required hardening temperature, rapid cooling or quenching process, followed by tempering to develop the desired mechanical properties. The tempering process involves reheating the strip to a lower temperature and holding it for a selected period of time, to reduce the brittleness that can result from the hardening process.
The Company supplies strip in sheared form, with or without rounded edges. It can also be supplied edge-dressed, which is material where the normal blue-black (also referred to as blue-grey) oxidised finish from the hot rolling process has been removed, by a very effective in-line machining process. This can be done either before or after the tempering process. This gives a better surface finish and eliminates shear marks that can detract from the appearance and the overall performance of finished components or tools.
Manufacturing Process
We produce high carbon spring quenched and tempered steel strip for use in various industrial applications. This product is a derived form of steel that has been subjected to rigorous heating treatment and tempering process that increases the strength of the metal, whilst also making it more workable.
The hardened strip is able to resist impact, cutting, abrasion and penetration, as well as being capable of being bent, stretched and deformed. It is also highly resistant to shock of heavy machines.
In the production of hardened and tempered steel strips a high degree of consistency in both mechanical properties and surface finish is essential. Our plant is capable of producing this quality of strip at a very high level of throughput, whilst maintaining the required high levels of tolerance on edge camber and flatness.
The invention relates to a method for the continuous hardening and tempering of steel strip. For tempering, the strip is preheated in several temperature zones to temperatures which are lower than the required tempering temperature and subsequently exposed to the latter for a short time. In the preferred embodiment of the invention, the last temperature zone is matched in length to the strip passage speed such that the material only reaches the tempering temperature shortly before leaving it. In this way the duration of exposure to the tempering temperature is independent of the strip width and the hardness of the strip remains substantially constant along its length.
Surface Finish
Spring steel strips are a type of high-strength, resilient material used for many applications. They have excellent elasticity, which means they can bend and return to their original shape repeatedly without permanent deformation. They are also hard, and manufacturers typically produce them with tight tolerances to meet specific application requirements.
To make spring steel strip, hot rolled steel is processed through a series of mechanical and chemical processes. This produces the rolled strip, which is descaled to remove impurities and then subjected to cold rolling to reduce its thickness and obtain a desired surface finish. The cold rolling process also changes the mechanical properties of the strip, making it easier to work with.
The resulting strip may undergo heat treatment to improve its performance. This involves heating the strip to a high temperature (austenitizing) and then rapidly cooling it in water or Tinplate Steel Coil / Sheet oil to “freeze” its microstructure. The resulting hardened strip is then tempered by reheating it to a lower temperature, which relieves internal stresses and makes the strip stronger and more resilient.
Once the strip has been tempered, it is ready for use in the manufacture of a wide range of components, from clutch plate segments to traditional clock springs. Manufacturers supply spring steel strip in coils with a variety of dimensions and properties, and it is available with a wide range of surface finishes and edge conditions.
