Q235 vs. QT400

Attribute	Q235	QT400
Material Type	Carbon Steel	Ductile Iron
Tensile Strength (MPa)	375-500	400-600
Yield Strength (MPa)	235	250
Hardness (HB)	≤ 187	≤ 230
Application	Construction, machinery	Machine parts, automotive components

Introduction

When it comes to choosing the right material for construction or manufacturing projects, the selection of the right steel grade is crucial. Two commonly used steel grades are Q235 and QT400. While both have their own unique properties and applications, it is important to understand the differences between them to make an informed decision. In this article, we will compare the attributes of Q235 and QT400 to help you understand which one may be more suitable for your specific needs.

Chemical Composition

Q235 is a carbon structural steel that contains less than 0.22% carbon, 0.30-0.70% manganese, 0.045% phosphorus, and 0.050% sulfur. On the other hand, QT400 is a low alloy steel that contains 0.35-0.45% carbon, 0.60-0.90% manganese, 0.035% phosphorus, and 0.035% sulfur. The higher carbon content in QT400 gives it increased strength and hardness compared to Q235. However, the lower carbon content in Q235 makes it more ductile and easier to weld.

Mechanical Properties

Q235 has a tensile strength of 370-500 MPa and a yield strength of 235 MPa. It has a elongation of 26% and a reduction in area of 40%. On the other hand, QT400 has a tensile strength of 400-550 MPa and a yield strength of 250 MPa. It has an elongation of 20% and a reduction in area of 35%. While QT400 has higher strength and hardness, Q235 has better ductility and toughness, making it more suitable for applications that require bending or forming.

Applications

Q235 is commonly used in construction, machinery, and automotive industries due to its good weldability and formability. It is often used for making structural components, such as beams, columns, and panels. On the other hand, QT400 is preferred for applications that require higher strength and wear resistance, such as in mining equipment, agricultural machinery, and industrial tools. Its higher hardness makes it suitable for parts that are subjected to heavy loads and abrasive wear.

Heat Treatment

Q235 is not typically subjected to heat treatment as it is a low carbon steel. However, it can be annealed to improve its machinability and ductility. QT400, on the other hand, can be heat treated to improve its mechanical properties. It can be quenched and tempered to increase its hardness and strength, making it suitable for applications that require high wear resistance and toughness.

Cost

Q235 is more cost-effective compared to QT400 due to its lower alloy content and simpler production process. It is widely available and used in various industries, making it a popular choice for budget-conscious projects. QT400, on the other hand, is more expensive due to its higher alloy content and specialized heat treatment requirements. It is often used in applications where the higher cost is justified by the superior mechanical properties it offers.

Conclusion

In conclusion, both Q235 and QT400 have their own unique properties and applications. Q235 is a versatile and cost-effective option for projects that require good weldability and formability, while QT400 is preferred for applications that demand higher strength and wear resistance. The choice between the two will ultimately depend on the specific requirements of your project and the balance between cost and performance. By understanding the differences between Q235 and QT400, you can make an informed decision that will ensure the success of your project.