Welcome to the Online Metals “Materials
Talk” series! My name is Evan, and I am going to walk you
through a high-level understanding of steel, and the four major types designated by the
American Iron and Steel Institute (AISI). To simplify your understanding we will use
the acronym CAST: that includes Carbon, Alloy, Stainless, & Tool
Steel Carbon steel. As the name indicates, the main alloying ingredient
in this type of steel is carbon. Carbon steel is highly versatile, and its
uses and properties vary depending on its carbon content. As the carbon content rises, the steel becomes
harder and stronger. However, it does become less ductile, more
brittle and harder to weld. Also, the higher the carbon, the lower the
melting point of the steel. Carbon steel is further broken down into four
groups based on its carbon content: low/mild, medium, high, and ultra-high. Also known as Mild Steel, Low Carbon Steel
contains approximately 0.04–0.3% carbon. Because of this, it is malleable, ductile,
tough, very easy to weld, and one of the cheaper forms of steel (Ex. 1018 Steel) Medium carbon, carbon content of this metal
ranges from 0.31–0.6%, is stronger and harder than Mild Steel, but it is more difficult
to weld and form. It is common in large parts, forged parts,
and automotive components. (Ex. 1045) High or Carbon Tool Steel generally has a
range of 0.61-1.5% carbon. This material is extremely hard and brittle. But because of this it is very difficult to
bend, weld, or cut. Lastly, Ultra-High Carbon Steel has a carbon
content ranging from 1.51-2% and can be heat treated to exceptional hardness. Specialist knives, axles, and punches are
typically made from ultra-high carbon steel. Technically every steel is an alloy, but not
all steels are called “alloy steels.” The term refers to steels that have been alloyed
with elements in addition to carbon. The most common elements include manganese,
chromium, nickel, silicon, boron, molybdenum, and vanadium. Adding other elements to iron and carbon can
improve a range of properties including strength, hardness, toughness, wear resistance, corrosion
resistance, and hardenability. Alloy steels are broken down into two groups:
low-alloy and high-alloy. Low Alloy Steels – 1-5% alloy content, easily
weldable with appropriate precautions. High Strength Low Allow – not made to chemical
composition, but to mechanical properties High Alloy Steels – Alloy Levels in excess
of 10%, giving them outstanding properties Stainless Steel is steel that has a minimum
of 10.5% chromium. The high chromium and carbon content give
stainless steel its iconic corrosion resistance, hardness, and strength. There are six main types of stainless steel:
austenitic, super-austenitic, ferritic, duplex steel, martensitic and precipitation-hardening
martensitic. These differences are extremely technical
and often aren’t very relevant outside of welding but stay tuned for a Materials Talk
video dedicated to Understanding Stainless. You can generally find an alloy of stainless
steel for any project you could imagine. At present there are over 150 specific alloys
of stainless. This is why stainless steel is used in everything
from medical equipment, cheap knives at mall kiosks, to spacecraft and airplane hulls. Tool steel is particularly well-suited for
making tools because of its distinctive hardness, resistance to abrasion and ability to hold
a cutting edge at elevated temperatures. The four major alloying elements in tool steel
are tungsten, chromium, vanadium and molybdenum. Tool steel is often used by blade-smiths in
making knives, axes, swords, and more. According to AISI and SAE specifications,
there are six major types of tool steel based around how they are hardened or what they
are used for. Water Hardening, Cold-working, Shock Resistant,
High Speed, Hot Working, & Special Purpose. These grades are also assigned a letter designation
to help clarify what they are. Thank you for watching another Online Metals
Video. Please subscribe to our channel and leave
a comment below with questions or future video requests!
