How to Heat Treat High Carbon Steel Strip
From tiny washers to pant hangers, high carbon steel is found in many household items. It’s also used in automotive, manufacturing, and construction applications.
High carbon steel strip can be processed by various techniques including stretching, drawing, bulging and bending. The workability of such metals is mainly determined by their forming characteristics.
Mechanical Properties
High carbon steel strip is used in a wide range of applications. It is harder to shape than low carbon steel, but still moderately ductile, which means it can be stretched or compressed without breaking. This property is what makes it so useful in the manufacture of custom flat springs and clips, and sheet metal stampings. It also has excellent fatigue properties and can withstand very high levels of stress.
During the warm rolling process, the mechanical characteristics of the strip are greatly affected by the accumulated number of reductions/passes. When the accumulative effect of warm rolling exceeds 50%, the strip begins to lose its workability, and the tensile strength and yield strengths begin to decrease as a result of the loss of ductility.
Soft spheroidized annealed high carbon strip is in tended for applications requiring slight cold forming or when a stiff, springy product is required. This type of strip is produced to specified Rockwell hardness ranges, which may vary depending on the grade, microstructure and gauge.
The ductility of high carbon steel strip is improved when it undergoes cold rolling. This is achieved by elongating High carbon steel strip the grains of the strip, strain-hardening it, and then cooling it rapidly after rolling. This allows the material to regain some of its original ductility and provides it with better resistance to forming.
Heat Treatment
In order to achieve the hardness required, High carbon steel strip must be heat treated. There are a number of different heat treatments available, and each has its own benefits and drawbacks. Some of the most common include normalizing, annealing, quenching, and tempering.
A combination of heating the metal to a temperature higher than that at which it is at equilibrium with its environment and then cooling it quickly. This causes the formation of a martensite microstructure, which is much stronger than austenite and has a lower melting point. This makes the steel tougher and less brittle.
Heat treatment is a black art with varying interpretations, but the basic principles are clear. Ideally the material should be heated until it is non-magnetic and then cooled to 1475degF (800degC). Alternatively, it should be heated to 1575degF (855degC) and then cooled slowly to room temperature.
This allows the formation of a harder case and provides good ductility whilst allowing the steel to retain its strength and workability. However, this is very difficult to control in practice unless the heat treater knows exactly what they are doing and has the proper equipment. Using non-standard quench rates and/or low-temperature tempers can seriously reduce mechanical properties such as tensile strength, and should be avoided.
Annealing
In the annealing process, the steel is heated above its critical temperature and maintained there for a specific time. This causes atoms to migrate in the crystal lattice and decreases the number of dislocations, resulting in a change in hardness and ductility. The material is then allowed to cool down. The crystal grain size and phase composition in the resulting material will determine its final properties.
High carbon steel strip can be annealed to a wide range of tensile strengths/hardnesses in order to suit the component manufacturing processes and end-uses involved. The softer, more malleable condition allows the component to be formed into a variety of shapes while also reducing the strain on tooling used during the manufacturing process.
The annealing process may also be carried out in order to relieve internal stresses and strains that can develop within the material during previous heat treatment cycles, such as forging, welding or cold working. This can reduce the risk of distortion or cracking during subsequent processes and supports the longevity of the material.
This type of annealing is Tinplate Sheet supplier known as process annealing, sub-critical annealing or stress relief annealing. In this process the steel is heated above its critical temperature for a specified time and then slowly cooled in still air. This results in the formation of a martensite structure with low temperature gradients.
Cold Rolling
Cold rolling is a metal forming process that starts with hot-rolled and pickled steel strip. It is reduced to a specified thickness in cold mills that are either reversing or tandem (composed of up to five or six different stands). The strip is then tempered to improve its mechanical properties.
The cold-rolling process is more precise than hot-rolled, which results in a better surface finish and smaller tolerances. This makes it ideal for a variety of applications, including construction and machinery framing. It is also a popular choice for projects that require high formability.
Choosing the correct type of steel for your project requires consideration of several factors. You need to balance the strength and durability of the material with your budget constraints and project timelines. You should also seek expert advice and find reliable suppliers and fabricators to ensure that your project is successful.
It is crucial to stay up-to-date on new innovations and developments in the steel industry, as they can significantly impact the performance of your finished product. Understanding how different types of steel are produced and their suitable uses will help you select the best option for your next project. The right steel will enhance your design and contribute to its longevity. Keep informed by watching industry news and trends, and consult with professionals to make sure that you choose the right steel for your needs.
