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Basic knowledge of steel

Classification of steels
Finished wood
Building materials, screw steel, wire rod, plate, bar
Seamless pipe, welded pipe
Plates -- cold rolled plate / roll, medium plate, color coated sheet (galvanized sheet, colour coated plate, tin plated sheet, aluminium plated steel sheet), silicon steel, strip steel
Profiles: angle groove, H steel, Fang Gang, flat steel, ball flat steel
Special steel: structural steel, tool steel, die steel, spring steel, bearing steel, cold heading steel and hard wire
Steel is an iron carbon alloy with carbon content between 0.0218%-2.11%. In order to ensure its toughness and plasticity, carbon content is generally not more than 1.7%. The main elements of iron are iron, carbon, silicon, manganese, sulfur and phosphorus. There are many kinds of steel classification methods, and the main methods are as follows: seven kinds:
1, according to quality classification
2, according to the forming method classification: (1) forging steel; (2) cast steel; (3) hot rolled steel; (4) cold drawn steel.
4. Classification according to metallographic structure
5. Classification by purpose
6. Comprehensive classification
Quality steel
(including premium quality steel)
7, according to smelting method classification
Classification of Steel Applications
(1) structural steel for construction and engineering, referred to as construction steel, used for building metal structural parts for buildings, bridges, ships, boilers, or other works. Such as carbon structural steel, low alloy steel, steel and so on.
(2) structural steel for mechanical manufacture refers to the steel used to make structural parts on mechanical equipment. This kind of steel is basically high-quality steel or high quality steel, mainly high-quality carbon structural steel, alloy structural steel, easy to cut structural steel, spring steel, rolling bearing steel, etc.
It is used to make all kinds of tools, such as carbon tool steel, alloy tool steel, high speed tool steel, etc.. According to use can be divided into tool steel, die steel, tool steel.
Steel with special properties, such as stainless steel, acid resistant steel, heat resistant steel, high resistance alloy, wear-resistant steel, magnetic steel and so on.
This refers to the steel used in various industrial sectors, such as automobile steel, steel for agricultural machinery, aviation steel, chemical machinery steel, boiler steel, electrical steel, welding rod steel, etc..
According to the quality of the steel
Chemical composition of steel
In addition to the main chemical components of steel Fe iron, also contains a small amount of carbon (C), silicon (Si), manganese (Mn), phosphorus (P), sulfur (S) and oxygen (0), nitrogen (N), titanium (Ti) and vanadium (V) and other elements, these elements are the content is very few, but a great impact on the performance of steel.
Carbon is the most important element in determining the properties of steel. It affects the mechanical properties of steel such as strength, plasticity, toughness and so on. When the carbon content of steel is below 0.8%, with the increase of carbon content, the strength and hardness of steel increase, the plasticity and toughness decrease. But when the carbon content is greater than 1%, the strength of steel decreases with the increase of carbon content. Carbon steels for general engineering purposes are low carbon steels, including less than 0.25% carbon, low alloy steels and less than 0.52% carbon.
The useful elements in steel are manganese, silicon, vanadium and titanium. The amount of alloying can be smelted into low alloy steel. The main harmful elements in steel are sulfur, phosphorus and oxygen, so pay special attention to controlling the content. Phosphorus is one of the harmful elements in steel, mainly dissolved in ferrite strengthen. With the increase of phosphorus content, the strength and hardness of the steel increased, and the plasticity and toughness decreased significantly. Especially, the lower the temperature, the greater the impact on plasticity and toughness, and thus significantly increase the cold brittleness of steel. Phosphorus can also reduce the weldability of steel, but phosphorus can improve the wear resistance and corrosion resistance of steel. Sulfur is also a harmful element, a nonmetallic sulfide inclusion in steel, which reduces the mechanical properties of steel.
Due to the low melting point of sulfide, make the steel grain separation caused by thermal processing, steel caused by fracture, formation of thermal phenomenon called hot brittleness. Sulfur reduces the weldability, impact toughness, fatigue resistance and corrosion resistance of steel. Oxygen is the harmful elements in steel, mainly in non metallic inclusions, a small amount of ferrite in weld. Non-metallic inclusions reduce the mechanical properties of steel, especially toughness. Oxygen has a tendency to promote aging. The low melting point caused by oxides also makes the weldability of steel worse.
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