The ratio of the main constituent elements of Q345 steel is basically the same as that of 16Mn steel.
The difference is the addition of Ti, Nb, and V trace alloying elements.
Q345 steel is the replacement of the old grades of 14MnNb, 12MnV, 16MnRE, 16Mn, 18Nb, and other steels, not just the replacement of 16Mn. In terms of chemical composition, 16Mn and Q345 are also different. More importantly, there is a big difference in the thickness grouping size of the two steel materials according to the different yield strength, which will inevitably cause the change of the allowable stress of certain thickness materials. Therefore, it is not appropriate to simply apply the allowable stress of 16Mn steel to Q345 steel, and the allowable stress should be re-determined according to the new steel thickness grouping size.
The ratio of the main constituent elements of Q345 steel is basically the same as that of 16Mn steel. The difference is the addition of Ti, Nb, and V trace alloying elements. A small amount of Ti, V, and Nb alloy elements can refine the grains, improve the toughness of the steel, and greatly improve the comprehensive mechanical properties of the steel. Because of this, the thickness of the steel plate can be made larger. Therefore, the comprehensive mechanical properties of Q345 steel should be better than 16Mn steel, especially its low temperature performance is not available in 16Mn steel. The allowable stress of Q345 steel is slightly higher than that of 16Mn steel.
Q345 is a low alloy steel material commonly used in motor vehicles, bridges, ships, and construction. Also known as GB/T 1591, the Q signifies the yield point, and the 345 references the strength of yield. As such, it is essential to note that the yield value decreases as the material thickness increases.
Q345 Equivalent Materials
Q345 can also be replaced with equivalent materials, including A572 Grade 50 USA ASTM, Q355 China GB/T, and SPFC 590 Vietnam/Japanese JIS.
Characteristics of Q345
The yield strength of Q345 is where the material begins to deform plastically. Before hitting deformation, it will return to its original shape when stress is removed. For Q345, the yield strength is 345 MPa.
Like many in its grade, it will endure elongation before pulling apart, which typically occurs at 20 percent of its initial length. Q345 has a tensile strength rating of 470 to 660 MPa, which means that it can handle heavy-duty stress and use before ever failing.
The welding property of Q345 may be questioned by end-users, even though the welding properties are primarily affected by the chemical content. However, the production technology has rapidly and significantly improved after many years of research, which means that it is an excellent steel standard for structural purposes.
Q345 steel is from the 16 Mn steel grade, typically manufactured in a hot rolled steel coil or sheet or a hot rolled steel plate. It is an excellent choice when you need high-pressure durability.
Uses of Q345
Q345 has excellent mechanical properties, good performance in low temperatures, and excellent weldability and plasticity. It is most commonly used in building structures, low-pressure vessels, cranes, mechanical parts, bridges, ships, petroleum storage tanks, lifting machinery, power stations, mining machinery, general metal parts, and in other structures that are exposed to temperatures of -40 ℃ or below or experience high-loads.
As a old Chinese standards, 16Mn is edited from GB 1591-1988 “low alloy structural steel”, has now been replaced by Q345. Low alloy steel Q345 steel has 5 quality grades, which are represented by from Q345A to Q345E. It can be said that Q345 steel is the substitution of old brand steel of 12MnV, 14MnNb, 18Nb, 16MnRE, 16Mn and other steel types, rather than only 16Mn steel. Their corresponding foreign maters are showed below:
| GB | ASTM | JIS | EN | DIN |
| Q345A | Grade 50 | SPFC 590 | E335(St 52-3) | 1.0060 |
| Q345B | Grade 50 | SPFC 590 | S355JR | 1.0045 |
| Q345C | Grade 50 | SPFC 590 | S355JO | 1.0553 |
| Q345D | Grade 50 | SPFC 590 | S355J2 | 1.0577 |
| Q345E | Grade 50 | SPFC 590 | S355NL | 1.0546 |
The chemical element of Q345 steel is basically the same as that of 16Mn steel. The difference lies in the addition of Ti, Nb and V micro alloying elements, which can refine grain, improve toughness, and finally improve the mechanical properties of steel. In other words, the comprehensive mechanical properties of Q345 steel are better than that of 16Mn steel, especially its low temperature performance and allowable stress.
Standards comparison:
| Steel | C | Si | Mn | P | S | Cr | Ni | Cu | Nb | V | Ti | N | Mo |
| 16Mn | 0.12~0.20 | 0.20~0.55 | 1.20~1.60 | ≤0.045 | ≤0.045 | ≤0.30 | ≤0.30 | ≤0.30 | / | / | / | / | / |
| Q345B | ≤0.20 | ≤0.50 | ≤1.70 | ≤0.035 | ≤0.035 | ≤0.30 | ≤0.50 | ≤0.30 | ≤0.07 | ≤0.15 | ≤0.20 | ≤0.012 | ≤0.10 |
16Mn is a typical grade of low alloy high strength steel, mainly including 16Mn steel plate, 16Mn seamless tube and 16Mn forgings, they are widely used in the manufacture of medium and low pressure vessels and oil tanks as well as general mechanical structural parts.
The ratio of the main constituent elements of Q345 steel is basically the same as that of 16Mn steel. The difference is the addition of Ti, Nb, and V trace alloying elements.
Q345 steel is the replacement of the old grades of 14MnNb, 12MnV, 16MnRE, 16Mn, 18Nb, and other steels, not just the replacement of 16Mn. In terms of chemical composition, 16Mn and Q345 are also different. More importantly, there is a big difference in the thickness grouping size of the two steel materials according to the different yield strength, which will inevitably cause the change of the allowable stress of certain thickness materials. Therefore, it is not appropriate to simply apply the allowable stress of 16Mn steel to Q345 steel, and the allowable stress should be re-determined according to the new steel thickness grouping size.
The ratio of the main constituent elements of Q345 steel is basically the same as that of 16Mn steel. The difference is the addition of Ti, Nb, and V trace alloying elements. A small amount of Ti, V, and Nb alloy elements can refine the grains, improve the toughness of the steel, and greatly improve the comprehensive mechanical properties of the steel. Because of this, the thickness of the steel plate can be made larger. Therefore, the comprehensive mechanical properties of Q345 steel should be better than 16Mn steel, especially its low temperature performance is not available in 16Mn steel. The allowable stress of Q345 steel is slightly higher than that of 16Mn steel.
Q345 material and 16Mn steel are a kind of steel names. Their starting points are different. Q345 material is named from the yield strength of steel, Q stands for yield strength (initial letter of yield), 345 is the value of yield strength, which is 345 Mpa. However, 16Mn steel refers to 0.16% carbon content and 0.7% – 1.0% manganese content.
In addition, the name of 16Mn steel is the old national standard, that is, the former name, because the former national standard has requirements on the manganese content of this material, that is, the manganese content is between 0.7% – 1.0%. However, the new national standard does not require the manganese content of this material, so it does not need to be expressed in 16Mn steel, which is replaced by Q345 material.
Usually, I have friends who ask 16Mn steel, and I will explain to him. Of course, if there are certain requirements for manganese content of Q345 material, I will also screen for customers and try to meet his requirements.
Classification by quality grade: Q345 is low-alloy steel of ordinary quality, and 16Mn is high-quality low-alloy steel.
Q345 belongs to GB/T1591-94 low-alloy high-strength structural steel. 16Mn belongs to JB4726-2000 carbon steel low alloy steel forgings for pressure vessels. Looking at the standards, it should be clear that the two steels have different uses.
In comparison, 16Mn has stricter requirements for sulfur and phosphorus content, and stricter quality requirements. 16MN and Q345 are the same in general use, but only 16MN can be used for containers and boilers, because Q345 is not listed in GB150, if you want to use it, the procedure is very troublesome, and it is classified according to characteristics. Both are weldable low alloy high strength structural steel.
The starting point of the name is different
Q345 and 16Mn are a name for steel. Their starting points are different. Q345 is named from the yield strength of steel. Q stands for yield strength (the first letter of yield), and 345 is the value of yield strength. And 16mn refers to the carbon content of 0.16%, manganese content (0.7%-1.0%).
The name of 16mn is the old name of the national standard, that is, the previous name, because the previous national standard has requirements for the manganese content of this material, that is, the manganese content is between (0.7%-1.0%), and the new national standard has already There is no requirement for the manganese content of this material, so 16mn is not used to represent it, and q345 is used instead.
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