1. Carbon structural steel
The. Note representation method
Steel grades are represented by the Chinese pinyin “Q” which represents the yield strength, followed by the numerical value of the yield strength (in MPa).
The standard currently includes five classes: Q195, Q215, Q235, Q255 and Q275.
These qualities differ mainly in their chemical composition, particularly in their carbon content, as well as in their mechanical properties.
B. Main features and applications
Carbon structural steel is divided into quality grades based on sulfur and phosphorus content.
Carbon structural steel is a type of plain carbon steel that does not contain alloying elements, often referred to as plain carbon steel.
Among all types of steel, carbon structural steel has the lowest price and has adequate strength, good plasticity, toughness, processability and machinability. This type of steel has higher yields and is widely used in the manufacture of building structures, such as metal sheets, profiles (round, square, flat, hexagonal, grooved, angular, etc.), wire rod and non-standard profiles. It is commonly used to build factories, bridges and ships.
Generally, this type of steel is used directly in the hot-rolled state.
2. High quality carbon structural steel
Steel grades are represented by Arabic numerals or a combination of Arabic numerals and chemical element symbols. The average carbon content is indicated by two digits (in ten thousandths), for example, “08F”, “45”, “65Mn”.
The. Standard and Grade
The national standard GB/T699-1999 specifies technical conditions such as grade, chemical composition, mechanical properties, test methods and acceptance rules for high-quality carbon structural steel.
Currently, there are thirty-one grades in the standard, including “08F”, “45”, “85”, “70Mn” etc.
B. Main features and applications
High-quality carbon structural steel types differ mainly in their carbon content. High-quality carbon structural steel is typically divided into low-carbon steel (C ≤ 0.25%), medium-carbon steel (C 0.25-0.60%), and high-carbon steel (C > 0. 60%) based on its carbon content.
Low carbon steel is mainly used for cold working and welding structures. Surface carburizing can be carried out in the manufacture of wear-resistant parts.
Medium carbon steel is mainly used for mechanical components with higher strength requirements. Depending on the resistance required, it undergoes quenching and tempering treatments. High-carbon steel is mainly used in the manufacture of wear-resistant springs and mechanical components.
This steel is generally used in a heat-treated state. Sometimes the four grades “65”, “70”, “85” and “65Mn” are also called high-quality spring carbon steel.
High-quality carbon structural steel has high yield and wide application. It is mainly rolled or forged into simple shapes such as round, square and flat bars, which are further processed by end users into various parts and components.
This type of steel generally needs to undergo heat treatment, such as normalizing or quenching and tempering, before use. It is mainly used to manufacture general structural parts and components for mechanical products.
3. High-strength, low-alloy structural steel
The. Note representation method
The nomenclature of steel types consists of three parts in sequence: the Chinese pinyin “Q” which represents the yield limit, followed by the numerical value of the yield limit and, finally, the quality grade symbol (A, B, C, D, E). For example, Q390A and Q420E.
B. Standard and Nomenclature
The national standard GB/T1591-94 specifies technical requirements such as class, chemical composition, mechanical properties, test methods and acceptance rules for high-strength low-alloy structural steel.
Currently, the standard includes five classes: Q295, Q345, Q390, Q420 and Q460, which differ in their chemical composition and mechanical properties.
w. Main features and applications
High-strength low-alloy structural steel is a low-alloy steel produced by adding a small amount of alloying elements (generally no more than 3%) to carbon structural steel. In the past, it was called ordinary low-alloy steel or low-alloy structural steel.
This type of steel has a low carbon content (no more than 0.2%) and mainly contains vanadium, niobium, titanium, manganese, boron, etc. Compared with carbon structural steel, this type of steel has higher strength, good toughness, better processability, welding performance and corrosion resistance.
Low-alloy, high-strength structural steel products mainly include hot-rolled steel, bars and plates. These steel products are widely used in the manufacture of boilers, bridges, chemicals, mining, ships and other equipment.
4. Alloy structural steel
The. Note representation method
The nomenclature of steel grades consists of Arabic numerals and chemical element symbols. The average carbon content is indicated by two digits (in ten thousandths) at the beginning of the note.
The representation method for alloy elements is as follows:
- When the average content of the alloying element is less than 1.5%, only the element is indicated in the class name, without indicating the content;
- When the average alloying element content varies from 1.50-2.49% or 2.50-3.49%, the corresponding symbol is added after the alloying element symbol.
For example, the average carbon, chromium, manganese and silicon contents are 0.35%, 1.25%, 0.95% and 1.25%, respectively, for a given structural steel alloy, which is represented by the grade 35CrMnSi.
Likewise, carbon, chromium and nickel with average contents of 0.12%, 0.75% and 2.95%, respectively, are represented by the 12CrNi3 grade.
B. Standard and Grade
The national standard GB/T3077-1999 specifies technical requirements such as grade, chemical composition, mechanical properties, low magnification structure, surface quality, decarburization depth, non-metallic inclusions, etc., for alloy structural steel.
Currently, there are 77 grades in 24 steel groups (or steel types) in the standard. Steel groups are classified based on the alloying elements contained in the steel, and each group contains several grades. For example, the Cr steel group includes eight grades, such as “15Cr” and “50Cr”.
w. Main features and applications
Alloy structural steel is produced by adding one or more alloying elements to carbon structural steel to improve its strength, toughness and hardenability.
Depending on the chemical composition (mainly carbon content), heat treatment process and application, it can be classified into carburizing steel, quenched and tempered steel and nitriding steel.
Alloy structural steel products mainly include hot-rolled bars, thick plates, thin plates, cold drawn steel, forged flat steel, etc. This steel is mainly used to manufacture large mechanical components and widely used in various transmission parts and fasteners for automobiles, ships, heavy machinery, etc.
5. Spring steel
The. Note representation method
The nomenclature of alloy steels for tools uses the letter “G” for steel, followed by numbers that indicate the carbon content (in hundredths) and chemical symbols that indicate the alloying elements. For example, GCr15.
B. Standard and Grade
The national standard GB/T1299-2014 specifies technical requirements such as grade, chemical composition, mechanical properties, non-metallic inclusions, surface quality, heat treatment, etc., for alloy tool steels.
The standard includes 54 grades in eight categories: high-speed tool steel, hot work tool steel, cold work tool steel, plastic mold steel, maraging steel, bearing steel, stainless steel, and special purposes.
w. Main features and applications
Alloy tool steel is a type of steel that contains alloying elements such as chromium, molybdenum, vanadium, tungsten or cobalt to improve its hardness, wear resistance, toughness and heat resistance.
It is widely used in the manufacture of cutting tools, dies, molds and other components that require high hardness and wear resistance.
Different types of tool steel alloys have their own specific characteristics and applications.
- High speed tool steel is suitable for cutting tools that operate at high speeds, while hot work tool steel is used for high temperature applications such as forging and extrusion dies.
- Cold work tool steel is suitable for stamping and cold forming applications, and plastic mold steel is used in the manufacture of plastic injection molds.
- Bearing steel is used in the production of bearings, while maraging steel is used for aerospace and defense applications due to its high strength and toughness.
- Stainless steel is used in a variety of industries due to its resistance to corrosion, and special purpose steel is used in specialized applications such as welding and nuclear power plants.
6. Tool carbon steel
The. Note representation method
Carbon tool steel grades are represented by the pinyin letter “T” for the Chinese character “carbon,” Arabic numerals, and chemical symbols. Arabic numerals indicate the average carbon content (in thousandths).
B. Pattern and notes
The national standard GB1298-86 specifies the technical conditions for the grades, chemical composition, hardness, fracture, low magnification structure, decarburization depth, hardenability and surface quality of carbon tool steel. The standard includes eight classes: T7, T8, T8Mn, T9, T10, T11, T12 and T13.
w. Main features and applications
Carbon tool steel is a type of steel with a high carbon content. Its minimum carbon content is 0.65%, reaching up to 1.35%. In order to improve the overall performance of steel, 0.40-0.60% manganese is added to “T8” steel to obtain “T8Mn” steel.
When the working temperature of cutting tools made of carbon tool steel exceeds 250oC, the hardness and wear resistance of the tools (that is, the red hardness of the steel) decrease drastically and their performance deteriorates.
7. Alloy tool steel
The. Note representation method
The tool steel alloy class representation method uses alloy element symbols and Arabic numerals. The method of representing alloy element symbols is the same as that of alloy structural steel.
- When the average carbon content is less than 1.00%, the carbon content (in thousandths) is represented by an Arabic numeral at the beginning of the note.
- When the average carbon content is greater than 1.00%, the average carbon content is generally not indicated.
For example, the type of tool steel alloy with an average carbon content of 0.88% and chromium content of 1.50% is represented by “9Cr2”; the type of alloy tool steel with average carbon content of 1.58%, chromium content of 11.75%, average molybdenum content of 0.50% and average vanadium content of 0.23% is represented by “Cr12MoV.
B. Pattern and notes
The national standard GB1299-2000 specifies the technical requirements for alloy tool steel. The standard divides alloys into six groups based on their use: steel for measuring tools and cutting tools, impact-resistant tool steel, hot-work die steel, cold-work die steel, die steel non-magnetic and steel to plastic. molds, including a total of 35 degrees.
w. Main features and applications
Alloy tool steel not only has a high carbon content, but also a high content of alloying elements such as chromium, tungsten, molybdenum and vanadium.
Therefore, alloy tool steel has higher hardness, wear resistance and toughness than carbon tool steel, especially quenching and tempering ability and red hardness that cannot be achieved by carbon tool steel.
Alloy tool steel is classified into pressure processing steel (hot and cold pressure processing) and cutting processing steel according to the processing method.
The main varieties of steel are hot-rolled and forged round steel, square steel, flat steel, as well as cold-drawn and bright bar steel. This type of steel is mainly used for the manufacture of all types of molds for cold and hot deformation, as well as various measuring tools and cutting tools.
8. High Speed Tool Steel
The. Note representation method
The grade representation method of high-speed tool steel is the same as that of alloyed structural steel.
The national standard GB/T9943-88 includes 14 grades of high-speed tool steel, and GB/T9942-1988 and GB/T9941-1988 include two and three grades respectively, all of which are included in the 14 grades mentioned above.
According to the content of alloying elements and performance characteristics, high-speed tool steel can be divided into tungsten high-speed steel, molybdenum high-speed steel and super-hard high-speed steel.
B. Main features and applications
High speed tool steel is commonly known as “Feng steel”. Steel has a high carbon content, and the carbon content of most grades is not less than 0.95%. Steel also has a high content of alloying elements such as tungsten, molybdenum, chromium, vanadium and cobalt.
The main varieties of high-speed tool steel products include hot-rolled, forged, peeled, cold-drawn and bright steel bars; large cross section forged round steel and hot and cold rolled steel sheets.
High-speed tool steel is used to manufacture cutting tools (such as turning tools, milling cutters, broaches, reamers, twist drills, etc.), as well as wear-resistant molds, rollers and mechanical parts.
9. Bearing steel
The. Note representation method
Bearing steel is divided into four categories based on chemical composition and usage characteristics: high carbon and chromium bearing steel, carburized bearing steel, high carbon and chromium stainless bearing steel, and high carbon and chromium bearing steel. high temperature bearings.
The method of representing the grade of high carbon and chromium steel is to add the symbol “G” at the beginning of the grade, but the carbon content is not indicated. The chromium content is represented in thousandths, and the method of representing other alloying elements is the same as that of alloy structural steel. For example, the type of bearing steel with an average chromium content of 1.5% is “GCr15”.
B. Pattern and notes
At present, China's bearing steel standards include GB/T18254-2000 “Technical conditions for high carbon and chromium bearing steel”, GB/T3203-1982 “Technical conditions for carburized bearing steel”, GB/T3086 -1982 “Technical conditions for high carbon bearing steel”. Chromium Stainless Bearing Steel”, YB/T688 and GB/T1205 “Technical Conditions for High Temperature Bearing Steel”.
These standards include 15 types of bearing steel, including five types of bearing steel with high carbon and chromium content, such as “GCr15”; six grades of carburized steel for bearings, such as “G20CrMo”; two types of stainless steel with high carbon and chromium content, such as “9Cr18” and “9Cr18Mo”; and two types of high temperature bearing steel such as “Cr4Mo4V” and “Cr14Mo4”.
w. Main features and applications
Bearing steel has high hardness, tensile strength, contact fatigue resistance and wear resistance, as well as considerable toughness, meeting the requirements of corrosion resistance and high temperature performance under certain conditions.
The main varieties of bearing steel products are hot-rolled and forged round steel, cold-drawn round steel and wire.
10. Acid-resistant stainless steel
The. Note representation method
Stainless steel is the abbreviation for acid-resistant stainless steel.
B. Pattern and notes
At present, China's standards for stainless steel include 33 standards, such as GB/T1220-1992 “Stainless Steel Rods”, GB/T4237-1992 “Stainless Steel Hot-Rolled Plates”, GB/T3280-1992 “Hot-Rolled Plates cold stainless steel”, GB/T13296-1991 “Seamless stainless steel tubes for boilers and heat exchangers” and GB/T4356-1984 “Stainless steel flat bars.
Generally speaking, steel that is resistant to corrosion in weak media such as air, steam and water is called stainless steel, while steel that is resistant to corrosion in strong media such as acids, alkalis and salts is called acid-resistant steel or corrosion-resistant steel.
There are many types of stainless steel, which are classified according to the metallographic structure of the steel in accordance with the national standard GB/T13304-1999 “Steel Classification” of China and internationally recognized classification methods.
w. Main features and applications
The main varieties of stainless steel products are hot-rolled sheets and strips, cold-rolled sheets and strips, hot-rolled and forged bars and profiles, hot-rolled flat bars, seamless tubes and welded tubes.
Stainless steel has a wide range of applications, mainly used in the manufacture of petrochemical equipment and pipelines, equipment for the nuclear power industry, ship equipment, medical devices, tableware and other devices that require stainless and corrosion-resistant properties.
11. Heat resistant steel
The. Note representation method
The method of representing the grade of heat-resistant steel is the same as that of stainless steel.
B. Pattern and notes
In current national standards, there are three standards for making heat-resistant steel: GB/T1221-1992 “Heat-resistant steel rods”, GB/T4238-1992 “Heat-resistant steel plates” and GB/T8732-1988 “Steel for steam turbine blades”.
The standards make detailed provisions on technical requirements such as class, chemical composition, casting method, delivery status, mechanical properties, low power structure, superior forging test resistance and surface quality of heat-resistant steel, as well as special technical requirements on the demand side.
In the standard, heat-resistant steel is divided into four types according to the metallographic structure: austenite type, ferrite type, martensite type and precipitation hardening type, with a total of 46 degrees.
w. Main features and applications
Heat-resistant steel has good chemical stability at high temperatures, can resist oxidation and corrosion by other means, and has high strength. The main varieties of heat-resistant steel products are hot-rolled and forged profiles (round, square, etc.) and flat steels, hot-rolled and cold-rolled sheets and strips, seamless steel tubes, etc.
12. Silicon Steel for Electrical Use
The. Execution Standard and Notes
China's current standards for silicon steel for electrical use include GB/T5218-88 “Hot-rolled silicon steel sheets for electrical purposes”, GB/T2521-1996 “Cold-rolled magnetic steel sheets and strips with grain oriented and non-oriented”, and YB/T5224-93 “Grain-oriented silicon steel thin strip”, with a total of 72 grades.
B. Main features and applications
Silicon steel is a low-carbon iron-silicon soft magnetic alloy material. Carbon is a harmful element in silicon steel, and the carbon content in steel is generally no more than 0.015%. Silicon is the most effective element for increasing the strength of iron. Adding silicon to electrical steel can reduce eddy current losses and decrease iron loss from the material.
The direction of the iron crystal grain arrangement of the cold-rolled non-oriented silicon steel strip is random and disordered, and the strip has isotropy. It is mainly used to make the core of rotating machines. Silicon steel strips with low silicon content are used to manufacture small electric motors for household appliances, and silicon steel strips with high silicon content are used to manufacture generators and large electric motors.
The iron grains of cold-rolled grain-oriented silicon steel strip are oriented and arranged along the rolling direction. Compared with cold-rolled non-oriented silicon steel strip, its magnetic properties along the rolling direction are particularly excellent. It is mainly used to make transformer cores for power generation, transmission and distribution.
Thin strips of grain-oriented silicon steel (thickness no more than 0.20 mm) are mainly used to make transformer cores for various power sources, such as pulse transformers, magnetic amplifiers and converters operating at frequencies above 400 Hz.
