Steel is by far the most widely used material in the world. Today, CNC machining is one of the most popular manufacturing techniques. CNC steel parts are used in various industries, including the medical, automotive, and electronics industries. To choose the metal material that best suits your parts, you should first understand the properties of each type of steel. Now let’s get a look at it.
What is steel?
Steel, including carbon steel and alloy steel, is one of the most versatile materials in the world. Known for its high hardness, toughness, abrasion resistance and weldability, steel is ideal for parts with high stress, wear, and impact.
Carbon steel is made of iron and carbon, and the major component of steel is iron. Iron is soft and generally not useful as an engineering material. It needs to add small amounts of carbon to strengthen and convert it into steel. Carbon plays a key role in mechanical properties. The higher the carbon, the harder it is. Steel can be divided into three main categories, low carbon steel with 0.05-0.19% carbon content, medium carbon steel with 0.2-0.49% carbon content, and high carbon steel with more than 0.5% carbon content.
Alloy steel is made by adding alloy elements other than carbon, such as Si、W、Mn、Cr、Ni、Mo、V, 、Ti, to alter the wear resistance and corrosion resistance properties of steel, meaning it can be tailored to specific applications and selected suitable alloys to optimize a part’s performance. The variety of steel and its complex properties challenge designers to choose the right steel.
There are some examples of steel grades.
Q235 is low-carbon steel with high plasticity and low strength. It is widely used in mechanical parts that do not require high performance, such as instrument parts, pins, washers, pipes, joints, etc.
AISI1045 is a medium carbon steel, which can be quenched to HRC42~46. It has good mechanical properties and is commonly used to manufacture mechanical parts, such as shafts, gears, high-strength bolts, etc.
AISI4340 4340 alloy steel is characterized by high strength, superior toughness, and good weldability machinability. It is often used to manufacture power transmission gears, shafts, aircraft landing gear, and other structural parts.
There are many kinds of high-strength low-alloy steel. Some common ones include Q295， Q345，Q390， Q420 and Q460. These steels are high in strength and good corrosion resistance, and relatively low in cost.
Free-machining steels are often classified by their sulfur content and are commonly designated as AISI 11 or 12 series. Examples include AISI 1215 and AISI 12L14. These steels have good machinability and are easy to machine. They can improve chip formation and reduce tool wear.
Another group is wear-resistant steels; wear-resistant steels are often used in applications where resistance to abrasion and wear is critical, such as mining and construction equipment. Some common grades include AR400, AR500, and Hardox.
Bearing steels are high carbon chromium alloy steel; they are designed to have high hardness, wear resistance, fatigue strength, and good dimensional stability. Common are AISI 52100, AISI 8620, and SAE 52100.
Electrical steels are designed for electrical applications, such as transformers and motors. Some common grades include AISI 1010 and AISI 1020. These steels have high magnetic permeability and low electrical conductivity.
Tool steels: Tool steels are designed to have high hardness, wear resistance, and toughness, as well as good dimensional stability. Some common grades include AISI D2, AISI A2, and AISI O1. These steels are often used in cutting tools, dies, and moulds.
But steel will rust immediately when exposed to moisture and air. Therefore, steel parts are usually treated for rust prevention, such as oxidation blackening, electroplating, coating, etc. Special alloy stainless steel was developed to improve the rust resistance of steel. One of the great advantages of this metal is that it doesn’t rust.
Since stainless steel contains chromium (Cr) and nickel (Ni) elements, making parts strong and rust-proof is a good choice. And it can withstand high temperatures because it has a high melting point. Suitable for manufacturing parts that will be exposed to harsh environments. Stainless steel is highly corrosive and stain resistant and often used in critical sanitary and exterior situations. It is also available, making polished, brushed, and PVD applied in colour to give it a luxurious look.
What is the difference between stainless steel grades?
SS301, SS302, SS303, and SS304 stainless steel have excellent rust resistance. SS304 is the greatest rust-proof one. It is commonly used in sheet metals, food processing equipment, kitchen appliances and enclosures.
SS316 has higher corrosion resistance than SS304 because it contains molybdenum elements, making it a popular choice for making watercraft, medical parts, and food processing equipment.
SS420, SS430, and SS440C stainless steel are high-carbon martensitic stainless steel. Heat treatment can obtain high strength, good hardness and wear resistance. It is often used for making aircraft parts, medical parts, and knife blades.
SS630(17-4PH) is a martensitic precipitation hardening stainless steel. It can be a solution heat treatment to high strength and hardness levels and is often used for petroleum, chemical, paper and sea fisheries industries.
2205 duplex stainless steel is one of the most common duplex stainless steel grades. It is almost twice the strength of austenitic stainless steel and is commonly used in high-pressure and highly corrosion environments.
Conclusion
In summary, choosing the right materials for CNC machining is a rigorous and professional job. Consulting the material expert JC rapid is a good idea.