The so-called alloy steel pipe is to add some alloy elements on the basis of carbon steel, such as Si, Mn, W, V, Ti, Cr, Ni, Mo, etc., which can improve the strength, toughness, hardenability, weldability, etc. of the steel. performance. Alloy steel can be classified according to the content of alloy elements, and in industrial production and life, alloy steel will be used in specific industries, and it is also common to classify according to the purpose.
Classification according to the content of alloying elements
Low alloy steel: the total amount of alloy is less than 5%;
Medium alloy steel: the total amount of alloy is 5~10%;
High alloy steel: the total amount of alloy is higher than 10%.
Classification by purpose
Alloy structural steel: low alloy structural steel (also known as ordinary low alloy steel); alloy carburizing steel, alloy quenched and tempered steel, alloy spring steel; ball bearing steel
Alloy tool steel: alloy cutting tool steel (including low alloy cutting tool steel, high-speed steel); alloy die steel (including cold die steel, hot die steel); steel for measuring tools
Special performance steel: stainless steel, heat-resistant steel, wear-resistant steel, etc.
Alloy steel number
Low alloy high strength structural steel
Its brand name is arranged in order by three parts: the Chinese pinyin letter (Q) representing the yield point, the yield limit value, and the quality grade symbol (A, B, C, D, E). For example, Q390A means low-alloy high-strength structural steel with yield strength σs=390N/mm2 and quality grade A.
Alloy structural steel
Its brand name consists of three parts: "two digits, ten element symbols + numbers". The first two digits represent 10,000 times the average carbon mass fraction in the steel, the element symbol indicates the alloying elements contained in the steel, and the numbers behind the element symbol indicate 100 times the average mass fraction of the element. When the average mass fraction of alloying elements is less than 1.5%, generally only the elements are indicated but not the numerical value; when the average mass fraction is ≥1.5%, ≥2.5%, ≥3.5%, ..., 2 and 3 are correspondingly marked behind the alloying elements , 4, . . . For example, 40Cr has an average carbon mass fraction Wc=0.4%, and an average chromium mass fraction WCr<1.5%. If it is high-grade high-quality steel, add "A" at the end of the grade. For example, 38CrMoAlA steel belongs to high-grade high-quality alloy structural steel.
Rolling bearing steel
Add "G" (the first letter of the Chinese pinyin of the word "roll") in front of the brand name, and the number behind it indicates a thousand times the mass fraction of chromium, and the mass fraction of carbon is not marked. For example, GCr15 steel is a rolling bearing steel with an average mass fraction of chromium WCr=1.5%. If chromium bearing steel contains alloying elements other than chromium, the expression method of these elements is the same as that of general alloy structural steel. Rolling bearing steels are all high-grade high-quality steels, but "A" is not added after the grade.
Alloy tool steel
The difference between the numbering method of this type of steel and the alloy structural steel is that when Wc<1%,one digit is used to indicate the thousand times the mass fraction of carbon; when the mass fraction of carbon is ≥1%,it is not marked . For example,Cr12MoV steel has an average carbon mass fraction of Wc=1.45%~1.70%, so it is not marked;the average mass fraction of Cr is 12%, and the mass fractions of Mo and V are both less than 1.5%. Another example is 9SiCr steel, its average Wc=0.9%,and the average WCr is <1.5%.However,high-speed tool steel is an exception,and its average carbon mass fraction is not marked no matter how much it is.Because alloy tool steel and high-speed tool steel are high-grade high-quality steel,there is no need to mark "A" after its grade.
Stainless steel and heat-resistant steel
The number in front of this type of steel grade indicates a thousand times the carbon mass fraction. For example,3Crl3 steel means that the average mass fraction Wc=0.3%,and the average mass fraction WCr =13%.When the mass fraction of carbon Wc ≤ 0.03% and Wc ≤ 0.08%,it is indicated by "00" and "0" in front of the brand,such as 00Cr17Ni14Mo2,0Cr19Ni9 steel, etc.
Post time: Mar-13-2023