What is Q235?

What is Q235?

Q235 steel is a kind of carbon structural steel. It is equivalent to A3 and C3 steel in the old standard gb700-79, and the Russian toct brand is used. Q in the steel grade represents the yield strength. In general, the steel is directly used without heat treatment.

Q235 ordinary carbon structural steel is also called A3 steel.

Ordinary carbon structural steel plate is a kind of steel material.

Q represents the yield limit of this material, and the following 235 refers to the yield value of this material, which is about 235mpa. The yield value decreases with the increase of the thickness of the material. Due to the moderate carbon content, good comprehensive properties, good combination of strength, plasticity and welding properties, it is widely used.

The yield strength decreases with the increase of the thickness of the material (the yield strength is 235mpa when the plate thickness / diameter is ≤ 16mm; 225MPa is the yield strength when the thickness is 16mm < plate thickness / diameter ≤ 40mm; 215mpa is the yield strength when 40mm < plate thickness / diameter ≤ 60mm; 205mpa is the yield strength when 60mm < plate thickness / diameter ≤ 100mm; 195mpa when the plate thickness / diameter is ≤ 150mm; 195mpa when the thickness / diameter is less than 150mm; and ≤ 200mm when the thickness / diameter is less than 150mm The yield strength is 185mpa).

Due to its low carbon content, good comprehensive properties, good combination of strength, plasticity and welding properties, it is widely used.

It is composed of Q + number + quality grade symbol + deoxidation method symbol. Its steel grade is prefixed with "Q" to represent the yield point of the steel, and the subsequent number represents the yield point value in MPa. For example, Q235 represents the carbon structural steel with yield stress (σ s) of 235 MPa.

If necessary, the symbol indicating the quality grade and deoxidation method can be marked after the steel grade.

The quality grade symbols are a, B, C and D.

Symbol of deoxidation method:

• F stands for rimmed steel;
• B represents semi killed steel;
• Z is killed steel;
• TZ stands for special killed steel.

Killed steel can not be marked, that is, Z and TZ can not be marked. For example, q235-af stands for class a rimmed steel.

Carbon steel for special purposes, such as bridge steel, marine steel, etc., basically adopts the expression of carbon structural steel, but the letter indicating the purpose is added at the end of steel grade.

According to GB / T 700-2006 standard, carbon structural steel Q235 is divided into four grades according to metallurgical quality: A, B, C and D.

Q235: Grade A, B, C and D (GB / T 700-2006)

• Q235A contains C ≤ 0.22% Mn ≤ 1.4% Si ≤ 0.35% s ≤ 0.050, P ≤ 0.045
• Q235B grade contains C ≤ 0.20% Mn ≤ 1.4% Si ≤ 0.35% s ≤ 0.045 P ≤ 0.045 (with the consent of the demander, the carbon content may not be greater than 0.22%)
• Q235C contains C ≤ 0.17% Mn ≤ 1.4% Si ≤ 0.35% s ≤ 0.040, P ≤ 0.040
• Q235D contains C ≤ 0.17% Mn ≤ 1.4% Si ≤ 0.35% s ≤ 0.035, P ≤ 0.035

There are many examples of cold working dies made by low carbon martensite hardening process in China.

The thickness of Mo CR bowing layer is more than 100 μ m, the surface Mo Cr content can reach 20%, Cr content can reach 10%, the carbon content of supersaturated carburizing surface is more than 2.0%, the surface composition is close to molybdenum high speed steel, and the surface hardness is up to 1300hv after quenching and tempering, More than general metallurgical high speed steel. The wear test shows that the friction coefficient increases with the increase of contact stress, and the average relative wear resistance is 2.2 times of GCr15 carburized and quenched steel.

The main uses of Q235 are as follows:

• ① It is widely used in construction and engineering structure, or mechanical parts with low performance requirements. C. Grade D steel can also be used as some professional steel.
• ② It can be used for all kinds of mold handle and other unimportant mold parts.
• ③ Q235 steel is used as punch material. After quenching, it can be directly used without tempering. The hardness is 36 ~ 40HRC, which solves the problem of punch cracking in use.

Standard of Q235

Brand			Q235 （ GB/T 700-2006 Carbon structural steel)
Grade			A	B	C	D
Deoxidation method			F 、 Z	F 、 Z	Z	TZ
Chemistry component	C		≤ 0.22	≤ 0.20	≤ 0.07	≤ 0.07
	Si		≤ 0.35	≤0.35	≤0.35	≤ 0.35
	Mn		≤ 1.40	≤ 1.40	≤ 1.40	≤ 1.40
	P		≤ 0.045	≤ 0.045	≤ 0.045	≤ 0.045
	S		≤ 0.050	≤ 0.050	≤ 0.050	≤ 0.050
yield strength	thick degree or straight path	≤ 16	≥ 235MPa
		＞ 16~40	≥ 225MPa
		＞ 40~60	≥ 215MPa
		＞ 60~100	≥ 215MPa
		＞ 100~150	≥ 195MPa
		＞ 150~200	≥ 185MPa
tensile strength			370~500MPa
Posthumous elongation rate	thick degree or straight path	≤ 40	≥ 26%
		＞ 40~60	≥ 25%
		＞ 60~100	≥ 24%
		＞ 100~150	≥ 22%
		＞ 150~200	≥ 21%
to attack test	Temperature (℃)		—	+20	0	-20
	Impact energy J		—	≥ 27

Source: China Pipe Fittings Manufacturer – Yaang Pipe Industry Co., Limited (www.yaang.com)

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