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How much do you know about steel?(二)
2022-06-29
Section 1 Classification of Steel

一. Ferrous and non-ferrous metals

1. Black metal

refers to an alloy of iron and iron. Such as steel, pig iron, ferroalloy, cast iron, etc. Both steel and pig iron are alloys based on iron and with carbon as the main added element, collectively referred to as iron-carbon alloys.

Pig iron refers to a product made by smelting iron ore in a blast furnace, which is mainly used for steelmaking and casting.

The cast iron is smelted in an iron melting furnace to obtain cast iron (a liquid iron-carbon alloy with a carbon content greater than 2.11%), and the liquid cast iron is cast into a casting, which is called a 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.

Iron-carbon alloys with a carbon content of less than 2.11% are called steels. The pig iron for steelmaking is put into a steelmaking furnace and smelted by a certain process to obtain steel. Steel products include ingots, continuous casting billets and direct casting into various steel castings. Generally speaking, steel generally refers to steel that is rolled into various types of steel.


2. Non-ferrous metals

Also known as non-ferrous metals, it refers to metals and alloys other than ferrous metals, such as copper, tin, lead, zinc, aluminum, as well as brass, bronze, aluminum alloys and bearing alloys. In addition, chromium, nickel, manganese, molybdenum, cobalt, vanadium, tungsten, titanium, etc. are also used in the industry. These metals are mainly used as alloy additions to improve the performance of metals. Among them, tungsten, titanium, molybdenum, etc. are mostly used to produce cutting tools. of cemented carbide. The above non-ferrous metals are all called industrial metals, in addition to precious metals: platinum, gold, silver, etc. and rare metals, including radioactive uranium, radium, etc.

Second, the classification of steel

In addition to iron and carbon, the main elements of steel include silicon, manganese, sulfur, phosphorus, etc. There are various classification methods of steel, and the main methods are as follows:

1. Classification by quality

(1) Ordinary steel (P≤0.045%, S≤0.050%)

(2) High-quality steel (both P, S ≤ 0.035%)

(3) High-grade high-quality steel (P≤0.035%, S≤0.030%)


2. Classification by chemical composition

(1) Carbon 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 alloy elements ≤ 5%); b. Medium alloy steel (total content of alloy elements > 5-10%); c. High alloy steel (total content of alloy elements > 10%).


3. Classification by forming method:

(1) Forged steel; (2) Cast steel; (3) Hot rolled steel; (4) Cold drawn steel.


4. Classification by metallographic organization

(1) Annealed state: a. Hypo-eutectoid steel (ferrite + pearlite); b. Eutectoid steel (pearlite); c. Hypereutectoid steel (pearlite + cementite); d. Lai Tensitic steel (pearlite + cementite).

(2) Normalized state: a. pearlitic steel; b. bainitic steel; c. martensitic steel; d. austenitic steel.

(3) No phase transition or partial phase transition


5. Classification by use

(1) Steel for construction and engineering: a. Ordinary carbon structural steel; b. Low alloy structural steel; c. Reinforced steel.

(2) Structural steel

a. Steel for machinery manufacturing: (a) quenched and tempered structural steel; (b) case-hardened structural steel: including carburized steel, ammonia-impregnated steel, and surface quenched 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. electrothermal 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. 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) 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) electrothermal alloy steel; (d) electrical steel; (e) high manganese wear-resistant steel.


7. Classification by smelting method

(1) By furnace type

a. Converter steel: (a) acid converter steel; (b) basic converter steel. Or (a) bottom-blown converter steel; (b) side-blown converter steel; (c) support-blown converter steel.

b. 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) According to the degree of deoxidation and the pouring system

a. Boiling steel; b. Semi-killed steel; c. Killed steel; d. Special killed steel.