The Rolling Characteristics of AISI Tool Steels
AISI tool steels, used in the manufacture of cutting, measuring, forming and processing tools for industries ranging from automotive and aerospace to general engineering and medical applications, demanded exceptional properties in applications subjected to mechanical, thermal and/or wear impacts. Tool steels are heat treated after forming and come in a variety of grades designed for different purposes. Depending on their composition, AISI tool steels can be divided into two main groups: high-speed steels and hot work tool steels.
The most common rolling process for AISI tool steels is hot rolling. Hot rolling is the process of heating the steel above its recrystallization temperature and then rolling it at temperatures typically in the range of 800-900°C (1470-1650°F). This reduces the grain size, improves the materials mechanical properties, and increases its maximum hardness. Hot rolling is convenient and easy to perform and can be used to produce a wide variety of shapes, as well as to improve the mechanical properties of the material.
High-speed steels are typically cold rolled for use in high-speed cutting tools, such as drills and taps. Cold rolling is the process of rolling hot-rolled steel at lower temperatures than normal rolling. This process is also known as cold finishing or cold working and involves passing the hot-rolled steel through a series of rolls to reduce the materials thickness and improve its surface quality, hardness, strength and other mechanical properties. The cold rolling process also reduces the grain size in the material, resulting in a sharper, more defined edge.
While cold rolling is often used for the production of high-speed cutting tools, hot rolling is more suitable for producing a variety of other tool steels, including hot work tool steels. Hot work tool steels are generally used in applications where greater wear resistance, toughness and impact strength are required. Hot rolling allows these steels to maintain their strength and toughness even at higher temperatures and helps to minimize deformation due to thermally induced stresses. Hot work tool steels are typically rolled at temperatures ranging from 900°C (1650°F) up to 1100°C (2000°F).
Although hot rolling is a convenient and fast way of forming products from AISI tool steels, it is important to keep in mind that the heat generated during the process can also cause a decrease in the material’s properties. This can occur due to metallurgical changes in the grain structure and chemical reactions. It is therefore important to use the correct rolling parameters and temperatures for the specific grade of tool steel to minimize potential changes in the material’s properties.
In conclusion, it can be said that rolling is an important part of the manufacturing process of tool steels. While hot rolling is often used to produce more general-purpose tool steels and cold rolling is used to produce high-speed cutting tools, it is important to choose the appropriate rolling process and temperatures for the specific grade of tool steel in order to ensure that the desired properties are achieved. Following this guidance will ensure that the tool steels will perform as expected in their applications, guaranteeing the highest level of reliability and quality.
