How are the materials of steel differentiated?

, The concept of steel: Steel is a steel ingot, billet or steel material that is made into various shapes, sizes and properties that we need through pressure processing.
Steel is an indispensable material for national construction and the realization of the four modernizations. It is widely used and comes in many varieties. 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 good operation and management work, which is divided into heavy rail, light rail, large section steel, medium section steel, small section steel, cold-formed steel section, high-quality section steel, wire rod, medium-thick steel plate, thin steel plate, electrical silicon steel sheet, strip steel , seamless steel pipes, welded steel pipes, metal products and other varieties.
2. Production methods of steel
Most steel processing involves pressure processing of steel, which causes plastic deformation of the processed steel (billets, ingots, etc.). According to the processing temperature of steel, it can be divided into cold processing and hot processing. The main processing methods of steel are:
Rolling: A pressure processing method in which the steel metal blank is passed through the gap between a pair of rotating rollers (in various shapes). Due to the compression of the rollers, the cross section of the material is reduced and the length is increased. This is the most commonly used production method for producing steel. It is mainly used. To produce steel profiles, plates and pipes. 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 require. Generally divided into free forging and die forging, they are often used to produce materials with large cross-sections such as large materials and blanks.
​ Drawing steel: It is a processing method that draws the rolled metal blank (shaped, tube, product, etc.) through the die hole into a reduced cross-section and an increased length. Most of them are used for cold processing.
Extrusion: It is a steel processing method in which metal is placed in a closed extrusion cylinder and pressure is applied on one end to extrude the metal from a specified die hole to obtain a finished product of the same shape and size. It is mostly used to produce non-ferrous metals and steel.
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, steel and non-ferrous metals.
, Ferrous metal refers to iron and iron alloys. Such as steel, pig iron, ferroalloy, cast iron, etc. Steel and pig iron are both alloys based on iron steel with carbon as the main added element. They are collectively called iron-carbon alloys.
Pig iron refers to a product made by smelting iron ore in a blast furnace. It is mainly used for steelmaking and steel castings. The cast pig iron is smelted in an iron melting furnace to obtain cast iron (liquid), and the liquid cast iron is poured into cast 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 a deoxidizer and alloying element additive for steel during steelmaking.
2. Put the pig iron for steelmaking into a steelmaking furnace and smelt it according to a certain process to obtain steel. Steel products include steel ingots, continuous casting billets and straight steel materials that are cast into various steel castings. Steel generally refers to steel rolled into various steel products. Steel Steel is a ferrous metal, but steel is not exactly equal to ferrous metal.
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 alloys 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 additives to improve the properties of the metal. Among them, tungsten, steel, titanium, molybdenum, etc. are mostly used in production Carbide for cutting tools. The above non-ferrous metals are called industrial metals. In addition to steel, there are precious metals: platinum, gold, silver, etc. and rare metals, including radioactive uranium, radium and other steel materials.
2. Classification of steel products
Steel is an iron-carbon alloy with a carbon content between 0.04% and 2.3%. In order to ensure its toughness and plasticity, the carbon content generally does not exceed .7%. In addition to iron and carbon, the main elements of steel include silicon, manganese, sulfur, phosphorus, etc. There are many ways to classify steel and various steel materials. The main methods are as follows:
, steel products are classified according to quality
() Ordinary steel (P≤0.045%, S≤0.050%)
(2) High-quality steel (P and S both ≤0.035%)
(3) High-grade high-quality steel (P≤0.035%, S≤0.030%)
2. Classification by chemical composition
() 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 > 5~0%); c. High alloy steel (total content of alloying elements > 0 %).
3. Steel is classified according to the forming method: () forged steel; (2)investment casting jewelry; (3) hot-rolled steel; (4) cold-drawn steel.
4. Steel materials are classified according to metallographic structure
() Annealed state: a. Hypoeutectoid steel (ferrite + pearlite); b. Eutectoid steel (pearlite); c. Hypereutectoid steel (pearlite + cementite); d. Leyte Tensite steel (pearlite + cementite).
(2) In normalized state: a. Pearlitic steel; b. Bainitic steel; c. Martensitic steel; d. Austenitic steel.
(3) Steel with no phase change or partial phase change 5. Classification by use
() Steel for construction and engineering: a. Ordinary carbon structural steel; b. Low alloy structural steel; c. Reinforced steel.
(2) Steel structural steel
a. Steel for machinery manufacturing: (a) Quenched and tempered structural steel; (b) Surface-hardened structural steel: including carburized steel, steel-hardened steel, and surface-hardened steel; (c) Easy-cut structural steel; (d) Cold plastic forming Steel: including cold stamping steel and cold heading steel.
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, and 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
() Ordinary steel
a. Carbon structural steel: (a) Q95; (b) Q25 (A, B); (c) Q235 (A, B, C); (d) Q255 (A, B); (e) Q275.
b. Low alloy structural steel
c. Ordinary structural steel for specific purposes
(2) High-quality steel (including high-grade high-quality steel)
a. Steel structural steel: (a) high-quality carbon structural steel; (b) alloy structural steel; (c) tension extension spring; (d) easy-cut steel; (e) bearing steel; (f) high-quality structural steel for specific purposes.
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. Classification by smelting method
() According to furnace type
a. Open hearth steel: (a) acidic open hearth steel; (b) alkaline open hearth steel.
b. Converter steel: (a) acidic converter steel; (b) alkaline 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 materials are classified according to the degree of deoxidation and pouring system
a. Boiling steel; b. Semi-killed steel; c. Killed steel; d. Special killed steel.
Four types of steel grades
Grade I HPB235 (Q235) steel bar, standard strength 235 N/mm2
Level II HRB335(20MnSi) 335
ⅢHRB400(20MNSiV) 400
Ⅳ RRB400(20MnSi) 400
Comprehensive classification: () Ordinary steel a. 3d printing carbon fiber ceramic engine parts structural steel: (a) Q95; (b) Q25 (A, B); (c) Q235 (A, B, C); (d) Q255 (A, B) ;(e) Q275. b. Low alloy structural steel c. Ordinary structural steel for specific purposes
(2) High-quality steel (including high-grade high-quality steel)
a. Structural steel: (a) high-quality carbon structural steel; (b) alloy structural steel; (c) spring steel; (d) easy-cut steel; (e) bearing steel;
(f) High-quality structural steel for specific purposes.
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