1. The concept of steel: steel is a material with various shapes, sizes and properties that we need through pressure processing of steel ingots, billets or steel.
Steel is an important material necessary for the construction of the country and the realization of the four modernizations. It is widely used and has a wide variety. According to different cross-sectional shapes, steel is generally divided into four categories: profiles, plates, pipes and metal products. In order to facilitate the organization of steel production, Order supply and do a good job management work, divided into heavy rail, light rail, large section steel, medium section steel, small section steel, cold-formed steel section steel, high-quality section steel, wire rod, medium and thick steel plate, thin steel plate, silicon steel sheet for electrical engineering, strip steel , Seamless steel pipe, welded steel pipe, metal products and other varieties.
2. Production method of steel
Most of the steel processing is the pressure processing of steel, which causes the processed steel (slab, ingot, etc.) to produce plastic deformation. According to the steel processing temperature, the steel can be divided into cold processing and hot processing. The main processing methods of steel are:
Rolling: A pressure processing method in which steel metal billets are passed through a pair of rotating rolls (various shapes), and the cross section of the material is reduced due to the compression of the rolls, and the length is increased. This is the most commonly used production method for producing steel. To produce steel profiles, plates, pipes. It is divided into cold rolling and hot rolling.
Forging steel: a pressure processing method that uses the reciprocating impact of a forging hammer or the pressure of a press to change the blank into the shape and size we need. Generally divided into free forging and die forging, it is often used for the production of large-scale steel, billet and other materials with larger cross-sectional dimensions.
Drawing steel: It is a processing method that draws rolled metal blanks (forms, tubes, products, etc.) through a die hole to reduce the cross section and increase the length, which is mostly used for cold working.
Extrusion: It is a processing method in which the steel is placed in a closed extruder and pressure is applied at one end to extrude the metal from a specified die hole to obtain a finished product with the same shape and size. It is mostly used to produce non-ferrous metal materials. .
1. Ferrous metals, steel and non-ferrous metals
Before introducing the classification of steel, let’s briefly introduce the basic concepts of ferrous metals, steel and non-ferrous metals.
1. Ferrous metals refer to iron and iron alloys. Such as steel, pig iron, ferroalloy, cast iron, etc. Both steel and pig iron are alloys based on iron steel and carbon as the main additive element, collectively referred to as iron-carbon alloys.
Pig iron refers to the product made by smelting iron ore in a blast furnace, and is mainly used for steelmaking and steel making castings. The cast iron is smelted in an iron melting furnace to obtain cast iron (liquid), and the liquid cast iron is cast into casting steel, which is called cast iron.
Ferroalloy is an alloy composed of iron and silicon, manganese, chromium, titanium and other elements. Ferroalloy is one of the raw materials for steelmaking. It is used as steel deoxidizer and alloy element additive during steelmaking.
2. Put the pig iron for steelmaking into a steelmaking furnace and smelt according to a certain process to obtain steel. Steel products include steel ingots, continuous casting billets, and straight steel products that are successively cast into various steel castings. Generally speaking, steel generally refers to steel rolled into various steels. Steel steel belongs to ferrous metals but steel is not exactly equal to ferrous metals.
3. Steel non-ferrous metals, also known as non-ferrous metals, refer to metals and alloys other than ferrous metals, such as copper, tin, lead, zinc, aluminum, brass, bronze, aluminum alloy, and bearing alloys. In addition, chromium, nickel, manganese, molybdenum, cobalt steel, vanadium, tungsten, titanium, etc. are also used in industry. These metals are mainly used as alloy additions to improve the properties of metals. Among them, tungsten, steel titanium, molybdenum, etc. are mostly used for production Cemented carbide for cutting tools. The above non-ferrous metals are called industrial metals. In addition to steel, there are precious metals: platinum, gold, silver and other rare metals, including radioactive uranium, radium and other steel materials.
Second, the classification of steel
Steel is an iron-carbon alloy with a carbon content of 0.04%-2.3%. In order to ensure its toughness and plasticity, the carbon content generally does not exceed 1.7%. In addition to iron and carbon, the main elements of steel include silicon, manganese, sulfur, and phosphorus. There are many kinds of steel classification methods, and the main methods are as follows:
1. Steel is classified by quality
(1) Ordinary steel (P≤0.045%, S≤0.050%)
(2) High-quality steel material steel (both P and S ≤0.035%).
(3) High quality steel (P≤0.035%, S≤0.030%).
2. Classified by chemical composition
(1) Carbon steel: Steel a. Low carbon steel (C≤0.25%); b. Medium carbon steel (C≤0.25~0.60%); c. High carbon steel (C≤0.60%).
(2) Alloy steel: a. Low alloy steel (total content of alloying elements ≤5%); b. Medium alloy steel (total content of alloying elements> 5-10%); c. High alloy steel (total content of alloying elements> 10 %).
3. Steel materials are classified according to forming methods: (1) Forged steel; (2) Cast steel; (3) Hot rolled steel; (4) Cold drawn steel.
4. Steel is classified by metallographic organization
(1) Annealed state: a. Hypoeutectoid steel (ferrite + pearlite); b. Eutectoid steel (pearlite); c. Hypereutectoid steel (pearlite + cementite); d. Ledite steel (pearlite + cementite).
(2) Normalized state: a. Pearlitic steel; b. Bainite steel; c. Martensitic steel; d. Austenitic steel.
(3) The steel has no phase change or partial phase change
5. Classified by purpose
(1) Steel for construction and engineering: a. Ordinary carbon structural steel; b. Low-alloy structural steel; c. Rebar steel.
(2) Steel structural steel
a. Steel for machinery manufacturing: (a) Quenched and tempered structural steel; (b) Surface hardened structural steel: including carburized steel, ammonia infiltrated steel, and surface hardening steel; (c) Free-cutting structural steel; (d) Cold plasticity Steel for forming: including steel for cold stamping and steel for cold heading.
b. Spring steel
c. Bearing steel
(3) Tool steel: a. Carbon tool steel; b. Alloy tool steel; c. High speed tool steel.
(4) Special performance steel: a. Stainless acid-resistant steel; b. Heat-resistant steel: including oxidation-resistant steel, heat-strength steel, valve steel; c. Electric heating alloy steel; d. Wear-resistant steel; e. Low temperature steel ; f. Electrical steel.
(5) Professional steel-such as steel for bridges, steel for ships, steel for boilers, steel for pressure vessels, steel for agricultural machinery, etc.
6. Comprehensive classification
(1) Ordinary steel
a. Carbon structural steel: (a) Q195; (b) Q215 (A, B); (c) Q235 (A, B, C); (d) Q255 (A, B); (e) Q275.
b. Low alloy structural steel
c. General structural steel for specific purposes
(2) High-quality steel: (including high-quality steel).
a. Steel structural steel: (a) High-quality carbon structural steel; (b) Alloy structural steel; (c) Spring steel; (d) Free-cutting steel; (e) Bearing steel; (f) Special-purpose high-quality structural steel.
b. Tool steel: (a) Carbon tool steel; (b) Alloy tool steel; (c) High speed tool steel.
c. Special performance steel: (a) stainless acid-resistant steel; (b) heat-resistant steel; (c) electric heating alloy steel; (d) electrical steel; (e) high manganese wear-resistant steel.
7. Classified by smelting method
(1) According to furnace type
a. Open-hearth steel: (a) Acid open-hearth steel; (b) Basic open-hearth steel.
b. Converter steel: (a) Acid converter steel; (b) Basic converter steel. Or (a) Bottom-blown converter steel; (b) Side-blown converter steel; (c) Top-blown converter steel.
c. Electric furnace steel: (a) Electric arc furnace steel; (b) Electroslag furnace steel; (c) Induction furnace steel; (d) Vacuum consumable furnace steel; (e) Electron beam furnace steel.
(2) Steel is divided according to the degree of deoxidation and pouring system
a. Boiling steel; b. Semi-killed steel; c. Killed steel; d. Special killed steel.