What's the difference between Q235 steel and 45 steel

1. Different characteristics:

Q235 steel: A, B, C, D four (GB/T 700-2006);

45 steel: commonly used carbon conditioned structural steel. The cold plasticity of the steel is general, annealing, normalizing than tempering is slightly better, with higher strength and better machinability, after appropriate heat treatment can obtain a certain toughness, plasticity and wear resistance, the material source is convenient.

Normalizing can improve the cutting performance of blank with hardness less than 160HBS. After quenching and tempering treatment, the comprehensive mechanical properties of the steel should be optimized in other medium carbon structural steel, but the steel hardenability is low, the critical quench diameter in water is 12~17mm, and there is a cracking tendency in water quench. When the diameter is greater than 80mm, after tempering or normalizing, its mechanical properties are similar, for medium and small mold parts after tempering treatment can obtain higher strength and toughness, and large parts, it is appropriate to normalize treatment, so the steel is usually used in tempering or normalizing state.

2. Different uses:

45 steel: is the commonly used material for shaft parts, it is cheap after tempering (or normalizing), can get better cutting performance, and can obtain higher strength and toughness and other comprehensive mechanical properties, quenching surface hardness can reach 45 ~ 52HRC.

Q235 steel: Can be used for a variety of abrasive tools handle and other non-essential abrasive parts. Once selected GCr15, 9SiCr, T8 and 45 steel, due to the workpiece bite die, stick die phenomenon, forging embryo is difficult to punch out from the die, resulting in plastic deformation, bending and fracture punch, short life.

3. Different specifications:

45 steel: Normalizing specification: normalizing temperature 850-870℃, hardness after normalizing 170-217HBS.

No. 45 steel is qualified if its hardness is greater than HRC55(up to HRC62) after quenching and before tempering. The highest hardness in practice is HRC55(high-frequency quenching HRC58). No. 45 steel should not use carburizing quenching heat treatment process.

Q235 steel: die steel quenching specification, quenching temperature is 950℃, salt bath furnace heating, 10%NaCl brine cooling quenching.

Cold press blank softening treatment specification: temperature 740~760℃, holding time 4~6h, with the cooling speed of 50~100℃/h, with the furnace down to temperature ≤600℃, air cooling, hardness before treatment ≤197HBS, hardness after treatment ≤156HBS.