There are many forms of steel:metal plates,plates,bars and beams of various geometric shapes,pipes,and of course,solid raw materials used by CNC in processing steel.Steel is used in so many applications and industries,so it is meaningful to have many different types of steel.But what is the difference between stainless steel and low-carbon steel?Free machining and tool steel?In this article,you will learn about many steel grades processed and how to successfully process steel grades with CNC.

What is steel?

Steel is a broad term for iron and carbon alloys.The carbon content(0.05%–2%by weight)and the addition of other elements determine the specific alloy of steel and its material properties.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 content is also usually high(at least 0.30%to 1.5%)to reduce the brittleness of steel and improve its strength.

The strength and hardness of steel is one of its most popular characteristics.It is they that make steel suitable for construction and transportation applications,because this material can be used for a long time under heavy and repeated loads.Some steel alloys,namely stainless steel varieties,are corrosion resistant,which makes them the best choice for parts working in extreme environments.

However,this strength and hardness will also prolong processing time and increase tool wear.Steel is a high-density material,which makes it too heavy in some applications.However,the strength to weight ratio of steel is very high,which is why it is one of the most commonly used metals in the manufacturing industry.

Steel type

Let's talk about many types of steel.As steel,carbon must be added to iron.However,the carbon content will be different,which will lead to great changes in its performance.Carbon steel usually refers to steel other than stainless steel,and is identified by the 4-digit grade of steel,more generally,low carbon steel,medium carbon steel or high carbon steel.

Mild steel:carbon content less than 0.30%by weight

Medium carbon steel:carbon content is 0.3–0.5%

High carbon steel:0.6%and above

The main alloying elements of steel are represented by the first digit of the four-digit grade.For example,any 1xxx steel,such as 1018,will use carbon as the main alloy element.1018 steel contains 0.14–0.20%carbon and a small amount of phosphorus,sulfur and manganese.This universal alloy is usually used for machining gaskets,shafts,gears and pins.

The easy-to-process grade carbon steel is re-phosphorized and re-phosphorized to break the chips into smaller pieces.This can prevent long or large chips from getting entangled with the tool during cutting.Easily machined steel can speed up processing time,but may reduce ductility and impact resistance.

stainless steel

Stainless steel contains carbon,but also contains about 11%chromium,which increases the corrosion resistance of the material.More chromium means less rust!The addition of nickel can also improve the rust resistance and tensile strength.In addition,stainless steel has good heat resistance and is suitable for aerospace and other applications in extreme environments.

According to the crystal structure of metal,stainless steel can be divided into five types.These five types are austenite,ferrite,martensite,duplex and precipitation hardening.The stainless steel grade is identified by three digits instead of four digits.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,also known as 18/8,because its chromium content is 18%and nickel content is 8%.303 stainless steel is a free-machining version of 304 stainless steel.The addition of sulfur reduces 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 for medical equipment,such as valve parts in machines and pipelines after proper processing.316 stainless steel is also used for machining nuts and bolts,many of which are used in aerospace and automotive industries.303 stainless steel is used for gears,shafts and other parts necessary for 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 available for different applications,but they are known for their hardness.Each of them can withstand repeated wear(the steel mold used for injection molding can withstand one million times or more materials)and has high temperature resistance.

A common application of tool steel is injection mold,which is processed from hardened steel CNC 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-term exposure to extreme temperatures.H13 mold is very suitable for advanced injection molding materials with high melting temperature,because it provides longer mold life than other steels–500000 to 1 million times.At the same time,S136 is stainless steel,and the die life exceeds one million times.This material can be polished to the highest level and used for special applications of parts requiring high optical clarity.

Steel treatment

Some of the most useful properties of steel come from additional processing and processing steps.These methods can be carried out before processing to change the properties of steel and make it easier to process.Please remember that hardening materials before machining will prolong processing time and increase tool wear,but steel can be processed after machining to increase the strength or hardness of the finished product.That is to say,it is important to consider any planned treatment in advance,and you need to apply it to achieve the necessary attributes for your parts.

heat treatment

Heat treatment refers to several different processes,involving manipulating the temperature of steel to change its material properties.One example is annealing,which is used to reduce hardness and increase ductility,making steel easier to process.The annealing process slowly heats the steel to the required temperature and maintains it for a period of time.The required time and temperature depend on the specific alloy and decrease with the increase of carbon content.Finally,the metal cools slowly in the furnace or is surrounded by insulating materials.

The normalizing heat treatment can eliminate the internal stress in the steel while maintaining higher strength and hardness than the annealed steel.During the normalizing process,the steel is heated to high temperature and then cooled by air to obtain higher hardness.

Quenched steel is another heat treatment process.You guessed it right.It hardens steel.It also increases strength,but also makes the material more brittle.The hardening process includes slowly heating the steel,soaking it at high temperature,and then immersing the steel in water,oil or saline solution for rapid cooling.

Finally,tempering heat treatment process is adopted to reduce the brittleness of quenched steel.Tempered steel is almost the same as normalizing:slowly heat it to the selected temperature,and then air cool the steel.The difference is that the tempering temperature is lower than other processes,which reduces the brittleness and hardness of tempered steel.

Precipitation hardening

Precipitation hardening improves the yield strength of steel.Some grades of stainless steel may contain PH values in their names,which means that they have precipitation hardening properties.The main difference between precipitation hardening steels is that they contain additional elements:copper,aluminum,phosphorus or titanium.There are many different alloys.In order to activate the precipitation hardening property,the steel is formed into the final shape and then subjected to aging hardening treatment.The aging hardening process heats the material for a long time to precipitate the added elements and form solid particles of different sizes,thus improving the strength of the material.

17-4PH(also known as 630 steel)is a common example of precipitation hardening grade of stainless steel.The alloy contains 17%chromium,4%nickel,and 4%copper,which is conducive to precipitation hardening.Due to increased hardness,strength and high corrosion resistance,17-4PH is used for helideck platforms,turbine blades and nuclear waste drums.

Cold working

The properties of steel can also be changed without applying a large amount of heat.For example,cold-worked steel makes it stronger through the work-hardening process.When the metal undergoes plastic deformation,work hardening will occur.This can be achieved by hammering,rolling or drawing metal.When machining,if the tool or workpiece is overheated,work hardening will also happen unexpectedly.Cold working can also improve the machinability of steel.Mild steel is very suitable for cold working.

Precautions for steel structure design

When designing steel parts,it is important to remember the unique characteristics of materials.The characteristics that make it very suitable for your application may require additional consideration of manufacturing design(DFM).

Due to the hardness of the material,it takes longer to process steel than other softer materials(such as aluminum or brass).You need to use the correct machine settings to optimize the processing quality and minimize tool wear.In fact,this means slower spindle speed and feed speed to protect your parts and molds.