Q235 steel is a kind of carbon structural steel. It is equivalent to the A3 and C3 steel in the old standard GB700-79 grades, and is also a grade used in Kazakhstan's TOCT system.
The "Q" in its steel number represents yield strength. Normally, this steel is used directly without heat treatment.
According to the GB/T 700-2006 standard, carbon structural steel Q235 is divided into four grades: A, B, C, and D according to metallurgical quality.
The chemical composition of each grade is as follows:
Q235 is divided into four levels: A, B, C and D (GB/T 700-2006)
Q235A: C ≤ 0.22%, Mn ≤ 1.4%, Si ≤ 0.35%, S ≤ 0.050, P ≤ 0.045
Q235B: C ≤ 0.20%, Mn ≤ 1.4%, Si ≤ 0.35%, S ≤ 0.045, P ≤ 0.045
(With purchaser consent, carbon content may exceed 0.20% up to 0.22%)
Q235C: C ≤ 0.17%, Mn ≤ 1.4%, Si ≤ 0.35%, S ≤ 0.040, P ≤ 0.040
Q235D: C ≤ 0.17%, Mn ≤ 1.4%, Si ≤ 0.35%, S ≤ 0.035, P ≤ 0.035
There are many examples in China of applying the intense quenching process of low-carbon martensitic steel to manufacture cold-work molds.
Double-layer glow ion penetration metal technology is used to perform Mo-Cr co-infiltration on the surface of the steel, followed by supersaturated carburizing, quenching, and tempering composite treatment.
The Mo-Cr diffusion layer thickness is more than 100 μm, surface Mo content reaches 20%, Cr content reaches 10%, supersaturated carburizing surface carbon content exceeds 2.0%.
The resulting surface composition is close to molybdenum-series high-speed steel, and the surface hardness after quenching and tempering is as high as 1300 HV, exceeding that of general metallurgical high-speed steel. Wear tests show that friction coefficient rises with contact stress, and the average relative wear resistance is 2.2 times that of GCr15 carburized and quenched steel.
Applications
Can be used for various grinding tool handles and other non-critical grinding tool parts.
Previously GCr15, 9SiCr, T8, and 45 steel were used. Due to mold bite and sticking during forging, it was difficult to eject blanks from the die, resulting in plastic deformation, bending, and breakage of punches, with short service life.
Traditional punches (10 pieces) could punch 800–1,200 bolts.
Later, Q235 steel was used as the punch material. After quenching, it can be used directly without tempering, with hardness 36–40 HRC. Each set of 10 punches can punch more than 2,000 bolts without failure. The typical failure mode becomes plastic deformation, effectively avoiding punch breakage and improving operator safety.
