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Q235 Carbon Steel: Composition, Characteristics, and Applications

304 stainless steel machining

Overview

Q235 is flexible, low-carbon steel with a carbon structure, commonly used without heat treatment as it will destroy the heat treatment of the weld. Due to its good plasticity, toughness, weldability, and strength, especially high-cost performance, it is widely used in construction and engineering structures, such as plates, steel bars, welded steel pipes, and other parts. 

What is Q235 Carbon Steel?

In China, Q235 carbon steel, which has the low carbon content is often used as structural steel, combined with good welding performance. The steel is, like ASTM A36 in the US and S235JR in Europe, in a completely comparable way. Q235 steel is usually carbonized up to 0.2% level, which is combined with manganese, silicon, sulfur, and phosphorus, etc., as other alloying elements. It finds widespread application in construction, machinery, and manufacturing industries in a variety of structural components like beams, columns, and plates, due to its reasonable strength, ductility, and low-cost. Q235 carbon steel can be processed by other methods such as welding, machining and forming to suite specific designs.

Why Is Q235 Carbon Steel Named Differently?

The name “Q235” is derived from the Chinese prizm, and it stands for the naming convention of China. Steel grades usually have a number that comes before the prefix. This number indicates the minimum yield strength of the steel. “Q” stands for “quality” and is given in the form of number that is the yield strength of at least 235 MPa. As a result the “Q235” carbon steel is a type of steel that has the minimum yield strength twenty three five mega pascals. This classification and standardization system makes use of this marking system for steel grades in manufacturing, construction, and other relevant areas in China.

Which Alloy Under the AISI Standard Is Similar to Q235 Carbon Steel?

The AISI equivalent to China’s Q235 carbon steel is generally considered to be AISI 1008 or AISI 1010. These American standards correspond closely to Q235 in terms of chemical composition and mechanical properties, offering similar ductility, strength, and welding capabilities. AISI 1008 contains approximately 0.08% carbon, while AISI 1010 has a slightly higher carbon content at about 0.10%. These low-carbon steels are utilized in various applications due to their balance of performance characteristics. However, for specific applications, detailed comparison and consultation with materials specifications are recommended to ensure full compatibility and adherence to required standards.

What Limitations Does Q235 Carbon Steel Have?

Compared to other steels, Q235 carbon steel is used extensively but it shows some limitations. Also, it possesses lower yield strength putting stringent limits on its application in environments demanding high strength mechanical properties and high load baring capacity. Therefore, meeting with a high risk of corrosion, especially in corrosive environments or high humidity, needs extra safety precautions in terms of coating or galvanization. Moreover, Q235 steel might be characterized by lowered toughness, which provides the reason to assume the negative toughness of the steel in low temperatures or under impact charges. Weldability concerns involving weld cracking and porosity are the issues that must be carefully addressed during the welding processes. It is also possible that smoothing steps such as additional machining or finishing are needed to achieve the desired surface finish as roughness makes the performance of high-quality steels. In spite of the above limitations, Q235 carbon steel is still widely used in some of the industries but you have to bear in mind that it is not appropriate for specific scenarios.

Chemical Composition of Q235 Carbon Steel

ComponentWt.%
Carbon (C)0.0 – 0.22
Manganese (Mn)0.0 – 1.40
Phosphorus (P)0.0 – 0.045
Sulfur (S)0.0 – 0.05
Silicon (Si)0.0 – 0.35
Iron (Fe)98.81 – 99.26

The Influence of Elemental Composition on the Properties of Q235 Carbon Steel

The explicit dependence of Q235 carbon steel on the elemental composition of its constituents is an established fact. Carbon content is the source of hardness, strength, and weldability, but Q235 steel has a relatively low content to provide decent strength combined with ductility. Manganese is used to give hardenability and overall mechanical properties, while silicon makes up the high strength and hardenability. Phosphorus and sulfur content are kept at minimum to ensure ductility and to avoid breakages. Besides that, trace elements such as copper, nickel, chromium, and vanadium are also involved in governance of corrosion resistance as well as the mechanical strength. Very high accuracy of control of these factors ends up with specific properties of Q235 steel that makes it applicable to a wide variety of uses.

Mechanical Properties of Q235 Carbon Steel

GradeYield StrengthTensile StrengthElongation %
Q235 Steel235 Mpa370-500 Mpa26

Physical Properties of Q235 Carbon Steel

Physical Properties
Density, g/cm3 (lb/in3)7.85 (0.284)
Melting point, °C (°F)1450-1530 (2640-2800)
Specific heat capacity, J/(Kg·K)470 at 20 °C (68 °F)
Electrical resistivity, μΩ·mabout 0.15 (20 °C)
Elastic modulus, GPa (ksi)200 (29 x 103)
Thermal conductivity, (W/m·K)53-49 (0-100 °C)
Coefficient of thermal expansion, (10-6/K)11.3-11.6 at 20-100 °C (68-212 °F)
Young’s modulus, GPa (ksi)200 (29 x 103)
Poisson’s ratio0.24-0.28

Processing Methods for Q235 Carbon Steel

Q235 carbon steel can be machined, welded and formed using the standard techniques, which is a great advantage when looking for high quality machined parts at unmatched prices. Machining is ensuring the shaping by means of drilling, milling, or turning, whereas welding methods facilitate the joining. The cold forming processes by means of bending and stamping make highly complex shapes, and the stress relieving makes de-stressing. Corrosion resistance is greatly increased by surface treatments as painting or galvanizing. These methods give the possibility to produce castings for the constitutions of structures, machine, and cars.

Applications of Q235 Carbon Steel

One of the areas where Q235 carbon steel is widely used is its diverse applications across various industries due these properties. It is used for making structural elements such as beams, columns and plates in construction due to its strength and favorable weldability. The production of machinery requires the use of Q235 for a variety of pieces such as gears, shafts, and fasteners, since it is machinable and so easy to afford. The automotive industries can benefit from it as a constituent of body panels and chassis due to its balance of strength and malleability. Besides, Q235 steel is also used in industry manufacturing equipments, agricultural machineries, and pipelines, due to its vast usages across different sectors which include critical applications for construction and mechanics which require reliable, low cost materials.

Equivalent Materials of Q235 Carbon Steel

EUEN 
USAGr.C

Germany

DIN, WNr

1.0028

1.0036

St34-2

USt37-2

Japan

JIS

SS330

STKM12A

FranceAFNOR

A34-2

S235JRG1

EnglandBS

CEW2BK

Fe360B

European oldENFe360BFU
ItalyUNI

Fe330

Fe360BFU

SpainUNEAE235B-FU
ChinaGB

A3

Q235

SwedenSS1312
PolandPNSt3SX
CzechiaCSN

11343

11373

AustriaONORM

St34RG

St37F

USt360B

NorwayNSNS12-122

Russia

GOST

16D

18kp

St3kp

InterISOFe360B
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