Q345B Description
Q345 is a kind of steel material. It is carbon alloy steel (C <0.2%), good overall performance, good low temperature performance, good cold stamping performance, good welding performance and good machinability.
Widely used in Bridges, vehicles, ships, buildings, pressure vessels, etc.
Q represents the yield of this kind of material. 345 in the back refers to the yield value of this kind of material, which is about 345MPa. The yield value decreases with the increase of the thickness of the material.
China Grade: Q345B
Q: The yield strength of steel
345: Yield strength value, unit MPa
B: The quality grade is B
Execution Standard: GB/T1591-2008
Application: Bridges, vehicles, ships, buildings
Advantages: good low temperature performance, cold stamping performance
This particular grade of steel is a ‘general purpose’ manufacturing steel in construction equipment field, such as Q345B is basic mateiral of making excavator bucket and long boom arms.
Q345 steel weldability, cold & hot workability and corrosion resistance are good. Widely used in bridges, ships, boilers, pressure vessels, petroleum storage tanks, lifting transport machinery and other high-load welded structural parts.
Yield Strength
A yield strength or yield point is the material property defined as the stress at which a material begins to deform plastically. Prior to the yield point the material will deform elastically and will return to its original shape when the applied stress is removed, Yield strength of Q345B is 345 MegaPascals. Like most steels of its grade, it suffers elongation before it pulls apart, typically at 20-21 percent of its initial length.
Tensile strength
The tensile strength of a material is the maximum amount of tensile stress that it can take before failure, for example breaking. Steel tensile strength is expressed in units of force divided by cross sectional area; in the Metric system, this unit is known as the Pascal. One Pascal is a Newton (the force needed to accelerate a one kilogram object to a velocity of one meter per second) per square meter. The tensile strength of Q345B steel is rated at 470 to 660 MegaPascals (where mega is million).
| Thickness (mm) | ||||
|---|---|---|---|---|
| Q345B | ≤ 16 | > 16 ≤ 35 | > 35 ≤ 50 | >50 |
| Yield strength (≥Mpa) | 345 | 325 | 295 | 275 |
| Tensile strength (Mpa) | 470-630 | |||
Steel tensile strength is expressed in units of force divided by cross sectional area; in the Metric system, this unit is known as the Pascal. One Pascal is a Newton (the force needed to accelerate a one kilogram object to a velocity of one meter per second) per square meter.
The tensile strength of Q345B steel is rated at 470 to 630 MegaPascals (where mega is million) and a yield strength (where the material starts to thin and pull like taffy) at 345 MegaPascals. Like most steels of its grade, it suffers elongation before it pulls apart, typically at 20-21 percent of its initial length.
Chemical composition for Q345B low alloy structural steel (Heat Analysis Max%)
| Main chemical elements composition of Q345B | |||||||
|---|---|---|---|---|---|---|---|
| C | Si | Mn | P | S | V | Nb | Ti |
| 0.20 | 0.55 | 1.00-1.60 | 0.040 | 0.040 | 0.02-0.15 | 0.015-0.060 | 0.02-0.20 |
The equivalent steel grade with Q345B are EN 10025-2 S355JR,ASTM A572/A572 A572 Grade 50 and DIN 17100 St52-3.
Worldwide equivalents of grade Q345B:
The density of Q345B steel is approximately 7.8 (where water is 1.0), and it is commonly available in thicknesses ranging from 2 mm to 12.7 mm (12.7 mm is approximately half-inch thick plates), with sheets typically sold in 1 to 1.35 meter wide splits.
| EU EN | USA – | Germany DIN,WNr | Japan JIS | France AFNOR | England BS | Canada HG | European old EN | Italy UNI | Belgium NBN | Spain UNE | China GB | Sweden SS | Inter ISO | Portugal NP | India IS | |||||||||||||||||||||
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| S355JR (1.0045) |
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The major benefit of this grade of steel is its mild temper. It’s easy to form and easy to weld.
Q345 Steel Properties and Introduction
Q345 steel is a Chinese GB standard Low Alloy High Strength Structural Steel, material density is 7.85 g/cm3, tensile strength is 470-630 Mpa, and yield strength is 345 MPa (datasheet tested with 16mm diameter steel bars or steel plates). According to GB/T 1591 – 2008, Q345 material has 5 quality grades: Q345A, Q345B, Q345C, Q345D and Q345E. “Q” is the first letter of Chinese Pinyin: “qu fu dian”, which means Yield Point, “345” is short for 345 MPa. For datasheet and specification, please see the tables below.
Q345 steel weldability, cold & hot workability and corrosion resistance are good. Widely used in bridges, ships, boilers, pressure vessels, petroleum storage tanks, lifting transport machinery and other high-load welded structural parts.
Table-1, Chemical Composition of Q345 Steel
| Steel Grade | Quality Grade | C | Si | Mn | P | S | Nb | V | Ti | Cr | Ni | Cu | N | Mo | B | Als |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Q345 | Q345A | 0.20 | 0.50 | 1.70 | 0.035 | 0.035 | 0.07 | 0.15 | 0.20 | 0.30 | 0.50 | 0.30 | 0.012 | 0.10 | – | – |
| Q345B | 0.035 | 0.035 | ||||||||||||||
| Q345C | 0.030 | 0.030 | 0.015 | |||||||||||||
| Q345D | 0.18 | 0.030 | 0.025 | |||||||||||||
| Q345E | 0.025 | 0.020 |
Notes: The P and S contents of profiles and bars can be increased by 0.005%, and the upper limit of Grade A steel can be 0.0045%.
Table-2, Q345 Mechanical Properties (≥ N/mm2)
| Steel Grade | Quality Grade | Ø ≤16 | 16 < Ø ≤ 40 | 40 < Ø ≤ 63 | 63 < Ø ≤ 80 | 80 < Ø ≤ 100 | 100 < Ø ≤ 150 | 150 < Ø ≤ 200 | 200 < Ø ≤ 250 | 250 < Ø ≤ 400 |
|---|---|---|---|---|---|---|---|---|---|---|
| Q345 | Q345A | ≥345 | ≥335 | ≥325 | ≥315 | ≥305 | ≥285 | ≥275 | ≥265 | – |
| Q345B | ||||||||||
| Q345C | ||||||||||
| Q345D | ≥265 | |||||||||
| Q345E |
Notes: Ø = Thickness or wire diameter in mm;
1 MPa = 1 N/mm2
Mechanical Properties: Tensile Strength (N/mm2)
| Grade | Quality Level | Ø ≤ 40 | 40 < Ø ≤ 63 | 63 < Ø ≤ 80 | 80 < Ø ≤ 100 | 100 < Ø ≤ 150 | 150 < Ø ≤ 250 | 250 < Ø ≤ 400 |
|---|---|---|---|---|---|---|---|---|
| Q345 | Q345A | 470 – 630 | 470 – 630 | 470 – 630 | 470 – 630 | 450 – 600 | 450 – 600 | – |
| Q345B | ||||||||
| Q345C | ||||||||
| Q345D | 450 – 600 | |||||||
| Q345E |
Ø mm, Elongation (≥%)
| Grade | Quality Level | Ø ≤40 | 40 < Ø ≤ 63 | 63 < Ø ≤ 100 | 100 < Ø ≤ 150 | 150 < Ø ≤ 250 | 250 < Ø ≤ 400 |
|---|---|---|---|---|---|---|---|
| Q345 | Q345A | ≥20 | ≥19 | ≥19 | ≥18 | ≥17 | – |
| Q345B | |||||||
| Q345C | ≥21 | ≥20 | ≥20 | ≥19 | ≥18 | ||
| Q345D | ≥17 | ||||||
| Q345E |
Q345 Equivalent
Q345 steel: Q345A, Q345B, Q345C, Q345D, Q345E equivalent to US ASTM, European Germany DIN, British BS, France NF, Japan JIS, and ISO Standard (For Reference)
| China | USA | Germany | Japanese | France | UK | ISO | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Standard | Grade | Standard | Grade | Standard | Grade (steel number) | Standard | Grade | Standard | Grade (steel number) | Standard | Grade (steel number) | Standard | Grade |
| GB/T 1591 – 2008 (Year) | Q345A | ASTM A529/A529M; ASTM A572/A572M; ASTM A588/A588M; ASTM A678/A678M; ASTM A808/A808M | Grade 50; Grade 50; Grade B; Grade D; A808M | DIN EN 10025-2;DIN 17100 | S355JR (1.0045), E355 (1.0060); St52-3 | JIS G3135 | SPFC590 | NF EN 10025-2 | S355JR (1.0045), E355 (1.0060); | BS EN 10025-2 | S355JR (1.0045), E355 (1.0060); | ISO 630-2 | S355C, S355D (S355) |
| GB/T 1591 – 2008 | Q345B | Ditto | Ditto | Ditto | Ditto | JIS G3135 | SPFC 590 | Ditto | Ditto | Ditto | Ditto | ISO 630-2 | S355C, S355D (S355) |
| GB/T1591 – 2008 | Q345C | Ditto | Ditto | DIN EN 10025-2; DIN 17100 | S355J0 (1.0553), E335 (1.0060); St52-3 | JIS G 3135 | SPFC590 | NF EN 10025-2 | S355JO (1.0553), E335 (1.0060) | BS EN 10025-2 | S355JO (1.0553), E335 (1.0060) | ISO 630-2 | S355D (S355) |
| GB/T 1591 – 2008 | Q345D | ASTM A656/A656M;ASTM A529/A529M | Type 7;Grade 50 | DIN EN 10025-2; DIN EN 10025: 1993; DIN 17100 | S355J0 (1.0553), E335 (1.0060); S355J2G3 (1.0570); St52-3 | JIS G 3135 | SPFC590 | NF EN 10025-2; NF EN 10025: 1993 | S355J0 (1.0553), E335 (1.0060); S355J2G3 (1.0570) | BS EN 10025-2; BS EN 10025: 1993 | S355J0 (1.0553), E335 (1.0060); S355J2G3 (1.0570) | ISO 630-2 | S355D (S355) |
| GB/T 1591 – 2008 | Q345E | ASTM A656/A656M;ASTM A529/A529M | Type 7;Grade 50 | DIN EN 10025-2; DIN EN 10025: 1993 | S355J2 (1.0553), S355K2 (1.0596), E335 (1.0060); S355J2G4 (1.0577), S355K2G3 (1.0595), S355K2G4 (1.0596) | JIS G3135 | SPFC 590 | NF EN 10025-2; NF EN 10025: 1993 | S355J2 (1.0553), S355K2 (1.0596), E335 (1.0060); S355J2G4 (1.0577), S355K2G3 (1.0595), S355K2G4 (1.0596) | BS EN 10025-2; BS EN 10025: 1993 | S355J2 (1.0553), S355K2 (1.0596), E335 (1.0060); S355J2G4 (1.0577), S355K2G3 (1.0595), S355K2G4 (1.0596) | ||
Notes: Q345 steel has been replaced by Q355 in the latest version of GB standard “GB/T 1591 – 2018”, the previous version is “GB/T 1591 – 2008”.
