An introduction:
These two types both belong to 16Mn steel grade and are usually produced in several hot rolled processes such as in steel plate and in steel coil/sheet. They are actually a Chinese standardized type of steel, and are becoming some of the most useful steels in the market today due to their mild temper, formability, and easy welding capability. This type of steel has robust mechanical and welding properties, thus providing good performance in structural applications. They are widely used as structural parts in producing ships, railways, bridges, automotives, steel tanks, and vessel containers among, other uses.
Q235 and Q345 both have the same chemical composition, both have the chemicals Carbon, Silicon, Manganese, Phosphorus and Sulfur. The main difference in their composition is the percentage of each chemical, outlined in the following charts:
| Steel Grade | Chemical Composition of Q235 | |||||
|---|---|---|---|---|---|---|
| C(≤) | Mn(≤) | Si(≤) | S(≤) | P(≤) | Cu(≤) | |
| A36 | 0.26 | 0.4 | 0.05 | 0.04 | 0.2min | |
| Q235A | 0.14~0.22 | 0.3~0.65 | 0.3 | 0.05 | 0.045 | |
| Q235B | 0.12~0.20 | 0.30~0.70 | 0.3 | 0.045 | 0.045 | |
| SS400 | – | – | 0.05 | 0.05 | ||
| Steel Grade | Chemical Composition of Q345 | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| C≤ | Mn | Si≤ | P≤ | S≤ | V | Nb | Ti | Al≥ | |
| A | 0.02 | 1.00~1.60 | 0.55 | 0.045 | 0.045 | 0.02~0.15 | 0.015~0.060 | 0.2 | – |
| B | 0.02 | 1.00~1.60 | 0.55 | 0.04 | 0.04 | 0.02~0.15 | 0.015~0.060 | 0.2 | – |
| C | 0.02 | 1.00~1.60 | 0.55 | 0.035 | 0.035 | 0.02~0.15 | 0.015~0.060 | 0.2 | 0.015 |
| D | 0.02 | 1.00~1.60 | 0.55 | 0.03 | 0.03 | 0.02~0.15 | 0.015~0.060 | 0.2 | 0.015 |
| E | 0.02 | 1.00~1.60 | 0.55 | 0.025 | 0.025 | 0.02~0.15 | 0.015~0.060 | 0.2 | 0.015 |
In this regard, these two types of steel also have different recommended applications due to their differing alloy contents:
• One should go for Q235 if the actual application is a type of metal construction that does not require much of steel strength, ie. tie rods, bolts and nuts, hooks/couplers, sleeves or welding parts.
• Opt for Q345 if you are building oil tanks, automotives, low-pressure vessels, cranes, mining machineries, power stations, building structures and other general parts. This is due to the fact that it has good mechanical properties, can perform in lower temperatures, has excellent plasticity as well as good welding properties. They are normally delivered in hot rolled or in normalizing state, and they can be used on areas with low temperatures that can go down to -40C.
Other properties
• Strengths
Q345 has a tensile strength range of 490-675 Mpa, while the Q235 has a 375-500 Mpa range.
Q345 has a yield strength of ≥ 345 Mpa, while the Q235 has a ≥ 235 Mpa.
Q345 has an elongation rate after fracture of ≥ 21%, while the Q235 has ≥ 26%.
There may be some end users who question the quality and the reliability of these steel types. Quite possibly this is due to the fact that each steel type has different chemical contents thus some properties such as welding properties may be compromised. We hope that the above information will be helpful and serve as a guide on which steel type would be perfect for each application.
At Shean, we usually use Q235 and Q345 as raw material, whether it is in form of steel pipe, steel wire or steel plate. Steel pipe is the material to produce earth screw and livestock corral, steel wire is the material to manufacture BBQ wire mesh grill, steel plate is the material to make post supports. We only use the most premium raw material to guarantee quality.
For further queries or information, please do not hesitate to contact us.