There are many forms of steel: sheet metal, plates, bars and beams of various geometric shapes, pipes, and of course, solid billets used in CNC steel processing. Steel is widely used, but what is the difference between different types of steel?
What is steel?
Steel is a general term for iron and carbon alloys. The amount of carbon (0.05% – 2% by weight) and the addition of other elements determine the specific alloy and material properties of the steel. Other alloying elements include manganese, silicon, phosphorus, sulfur and oxygen. Carbon increases the hardness and strength of steel, while other elements can be added to improve corrosion resistance or machinability. Manganese is also frequently present in large quantities (at least 0.30% to 1.5%) to reduce the brittleness of steel and increase its strength.
The strength and hardness of steel is one of its most popular characteristics. They make steel suitable for construction and transport applications because the material can be used for a long time under heavy and repeated loads. Some steel alloys, i.e. stainless steel varieties, are corrosion resistant, which makes them the best choice for parts operating in extreme environments.
However, this strength and hardness will also lead to longer processing time and increased wear of cutting tools. Steel is a high density material, which makes it too heavy for some applications. However, steel has a high strength to weight ratio, which is why it is one of the most commonly used metals in manufacturing.
Let's take a look at some of the various steels. To become steel, carbon must be added to iron. Although the amount of carbon varies, it leads to great differences in properties. Carbon steel usually refers to steel other than stainless steel, and is identified by the 4-digit grade of steel. It is more widely known as low, medium or high carbon steel.
Mild steel: less than 0.30% carbon by weight
Medium carbon steel: 0.3 – 0.5% carbon
High carbon steel: 0.6% and above
The main alloy elements of steel are represented by the first digit in the four digit grade. For example, any 1xxx steel, such as 1018, will use carbon as the main alloying element. 1018 steel contains 0.14 – 0.20% carbon and a small amount of phosphorus and sulfur, as well as manganese. This universal alloy is commonly used to machine gaskets, shafts, gears, and pins.
Easy to machine grade carbon steel is re vulcanized and re phosphated, so that the chips break into smaller pieces. This prevents long chips or large chips from becoming entangled with the tool during cutting. Free machining steels can reduce processing time, but may reduce ductility and impact resistance.
Stainless steel contains carbon, but it also contains about 11% chromium, which increases the corrosion resistance of the material. More chromium means less rust! Adding nickel can also improve rust resistance and tensile strength. In addition, stainless steel has good heat resistance, making it suitable for aerospace and other extreme environmental applications.
According to the crystal structure of metals, stainless steels can be divided into five types. The five types are austenite, ferrite, martensite, duplex and precipitation hardening. Stainless steel grades are identified by three digits instead of four. The first number represents the crystal structure and main alloy elements.
For example, 300 series stainless steel is austenitic chromium nickel alloy. 304 stainless steel is the most common grade because it contains 18% chromium and 8% nickel. 303 stainless steel is a free machining version of 304 stainless steel. Adding sulfur will reduce its corrosion resistance, so 303 stainless steel is more prone to rust than 304 stainless steel.
Stainless steel can be used in a wide range of industries. Type 316 stainless steel can be used in medical equipment, such as valve assemblies in machines and pipelines, if properly processed. 316 stainless steel is also used to machine nuts and bolts, many of which are used in the aerospace and automotive industries. 303 stainless steel is used for gears, shafts and other essential parts of aircraft and automobiles.
chisel tool steel
Tool steel is used to manufacture tools for various manufacturing processes, including die-casting, injection molding, stamping and cutting. There are many different tool steel alloys tailored for different applications, but they are known for their hardness. Each can withstand the wear of multiple use (the steel mold used for injection molding can withstand one million or more times of material injection) and has high temperature resistance.
A common application of tool steel is injection molding tools, which are machined from hardened steel CNC and used to produce the highest quality production parts. H13 steel is usually selected because of its good thermal fatigue performance - its strength and hardness can withstand long exposure to extreme temperatures.
H13 mold is very suitable for advanced injection molding materials with high melting temperature, because it provides a longer mold life than other steels - 500000 to 1 million injections. At the same time, S136 is stainless steel, and the tool life exceeds one million times. This material can be polished to the highest level for special applications where parts require high optical transparency.