Chemical properties of Q345R pressure vessel steel plate

2026-05-29 | More News

Q345R is common low alloy steel, it is the boiler pressure vessel commonly used steel type, the delivery state: hot rolled or normalization.

Q345R Appication:

Q345R steel plate is used in the inner tube of the multi-layer container, for the shell thickness is larger than 36mm for other compression elements (flanges, tube plates and flanges).
If the thickness of the cap is greater than 50mm, it should be used in the state of normalization: For steel plates used for multi-layer containers or for steel plates with a thickness of more than 60mm, each of the heat treated steel plates should be stretched and v-shaped Mouth impact test.
According to the design document, for steel plate with thickness greater than 80mm, ultrasonic testing can be added to steel plate thickness.
For steel plate thickness is 30 ~ 36 mm, ultrasonic testing requirement is not lower than level Ⅲ.
For steel plate thickness is greater than 36 mm, ultrasonic testing is required not lower than level Ⅱ.

Q345R Steel Introduction:

Q345R is a combination of 16Mng, 19 Mng and GB6654-1996, and GB150 specified the thickness range is 3 ~ 200mm. The limit value of the tensile strength with low carbon content and standard is no more than 540Mpa, and it has good weldability, in common conditions cold and hot crack are not easy to form. However, the same as the 20 # carbon manganese structure steel, with large thickness and in low ambient temperature working environment, it produces cold, hot cracks.

Q345R steel contains a certain amount of alloy elements, yield strength tends to be high, Therefore, we should review the real destrength ratio (real yield strength) from the quality guarantee certificate of the steel or the production unit (The ratio of the degree to the actual tensile strength).

Q345R Chemical composition% of the Product analysis of grade

Grade	C %	Si %	Mn %	Cu %	Ni %	Cr%	Mo %	V %
Q345R	0.20	0.55	1.2-1.7	0.30	0.30	0.30	0.08	0.050
	Ti %	Alt %	P %	S %	Nb
	0.030	0.020	0.025	0.010	0.050

Q345R Mechanical Property

Grade	Thickness(mm)	Min Yield	Tensile	Elongation	Min Impact Energy
					Degree	Min J
Q345R	3-16	345Mpa	510-640 Mpa	21%	0	41J
	16-36	325Mpa	500-630 Mpa	21%	0	41J
	36-60	315 Mpa	490-620 Mpa	21%	0	41J
	60-100	305 Mpa	490-620 Mpa	20%	0	41J
	100-150	285 Mpa	480-610 Mpa	20%	0	41J
	150-250	265 Mpa	470-600 Mpa	20%	0	41J

What is the difference between Q245R and Q345R?

Q245R and Q345R are both low alloy steel grades used for pressure vessel applications in China. While they have some similarities, there are differences in terms of composition, mechanical properties, and application. Here’s a comparison between Q245R and Q345R:

Chemical Composition:

Q245R: The chemical composition of Q245R typically includes carbon (C) content up to 0.20%, manganese (Mn) content ranging from 0.40-0.60%, silicon (Si) content up to 0.35%, phosphorus (P) content ≤0.025%, sulfur (S) content ≤0.015%, and trace amounts of other elements.

Q345R: The chemical composition of Q345R typically includes carbon (C) content up to 0.20%, manganese (Mn) content ranging from 0.50-1.60%, silicon (Si) content up to 0.55%, phosphorus (P) content ≤0.025%, sulfur (S) content ≤0.015%, and trace amounts of other elements.

Mechanical Properties:

Q245R: The minimum yield strength of Q245R is 245 MPa (35,500 psi), and the minimum tensile strength is 400-520 MPa (58,000-75,400 psi). The elongation at break is typically around 22%.

Q345R: The minimum yield strength of Q345R is 345 MPa (50,000 psi), and the minimum tensile strength is 510-640 MPa (74,100-92,800 psi). The elongation at break is typically around 21%.

Application:

Q245R: Q245R is primarily used for the fabrication of pressure vessels and boilers that operate at moderate temperatures. It is suitable for applications involving mediums such as liquefied petroleum gas (LPG), natural gas, and crude oil.

Q345R: Q345R is used for the production of pressure vessels and boilers that operate at high temperatures. It is suitable for applications involving mediums with higher operating temperatures, such as hydrogen, ammonia, and methanol.

What are the differences between Q345B and Q345R steel?

Q345B: It is a low-carbon alloy steel (c <0.2%), with good overall performance, low temperature performance, cold stamping performance, welding performance and machinability.
Q345R: It is a special plate for pressure vessels with a yield strength of 345MPa. Q345R pressure vessel steel has good comprehensive mechanical properties and technological performance. In addition to the tensile strength and elongation requirements higher than Q345 (16Mn) steel, it is also required to ensure impact toughness.

Difference in producing standard

Q345B: The external execution standard is: gb709, and the internal execution standard is: gb / t1591-94. Due to the implementation of the standard, such steel plates are allowed to be delivered with negative tolerances. The latest implementation standard is GB / T1591-2018.
Q345R: 16Mng and 16MnR, 19Mng merged into Q345R. It is ordinary low alloy steel, and is commonly used in boiler and pressure vessels. The delivery status is divided into hot rolled or normalized, which belongs to low alloy steel. The performance is similar to that of Q345 (16Mn), the tensile strength is between 510-640, the elongation is greater than 21%, and the zero-degree V-shaped impact energy is greater than 34J. Q345R process reference standard GB713-2014.

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