This page article highlights the significance of carbon steel structural products in industrial applications. It discusses the various grades and advantages of carbon steel structural, emphasizing its high strength, toughness, and excellent welding properties. The distinction structural is elucidated, along with the properties and composition of carbon steel. Additionally, it explores different types of carbon steel structures, their applications, and the chemical influences affecting their performance. The article concludes by emphasizing the importance of understanding carbon steel’s structural bending capabilities and its diverse shapes, offering insights into its practical use in various engineering projects.

What is carbon steel?

Carbon steel is an iron-carbon alloy with a carbon content ranging from 0.04% to 2.3%. To ensure its toughness and plasticity, the carbon content generally does not exceed 1.7%. In addition to iron and carbon, carbon steel contains elements such as silicon, manganese, sulfur, and phosphorus.

With a carbon content of less than 2.11%, carbon steel alloys contain no other alloying elements besides iron, carbon, and limited amounts of impurities such as silicon, manganese, phosphorus, and sulfur. Industrial-grade carbon steel typically contains 0.05% to 1.35% carbon. The performance of carbon steel primarily depends on its carbon content. As the carbon content increases, the steel’s strength and hardness increase, while its plasticity, toughness, and weldability decrease. Compared to other steel types, carbon steel was among the first to be used, offering a wide performance range, low cost, and extensive usage. It is suitable for various applications involving nominal pressures up to 32.0 MPa and temperatures ranging from -30 to 425°C, including mediums such as water, steam, air, hydrogen, ammonia, nitrogen, and petroleum products. Common grades include WC1, WCB, ZG25, high-quality steels 20, 25, 30, and low-alloy structural steel 16Mn.

Carbon Steel Structural Steel

Main Applications: Various engineering applications. Typically supplied in a hot-rolled and air-cooled state, requiring no additional heat treatment for direct use. These steels are divided into five grades based on their yield strength.

• Naming: Symbolic representation Q + minimum σS value — grade symbol + deoxidation level symbol, such as Q235AF.
• Grade Symbols: A, B, C, D (Grade D achieves high-quality steel standards).

High-Quality Carbon Structural Steel

Main Applications: Important machinery components. Mechanical properties of parts can be adjusted through heat treatment. Can be supplied in a hot-rolled and air-cooled state or annealed, normalized, etc. According to the national standard (GB/T699-1999), they are divided into three quality grades: high-quality steel, advanced high-quality steel A, and special high-quality steel E.

• Naming: Represented by two digits, where the two digits indicate the percentage of carbon in the steel. For example, 45 steel corresponds to WC=0.45%.
• Common Grades: 08F, 10#, 15#, 20#, 35#, 45#, 60#, etc.

Chemical Influence

The performance of carbon steel depends primarily on its carbon content and microstructure. In the annealed or hot-rolled state, as the carbon content increases, the steel’s strength and hardness increase, while its plasticity and impact toughness decrease. Weldability and cold bending properties deteriorate. Therefore, the carbon content is often limited for engineering structural steels. Residual and impurity elements in carbon steel, such as manganese, silicon, nickel, phosphorus, sulfur, oxygen, and nitrogen, also affect its properties. These effects sometimes reinforce each other, while other times they offset each other.

For example:

• Sulfur, oxygen, and nitrogen increase the steel’s susceptibility to hot brittleness, while moderate amounts of manganese can reduce or partially offset it.
• Residual elements, except for manganese and nickel, reduce the steel’s impact toughness and increase its susceptibility to cold brittleness.
• Apart from sulfur and oxygen, which reduce strength, other impurity elements generally increase the steel’s strength to varying degrees.
• Almost all impurity elements decrease the steel’s plasticity and weldability.

General Carbon Structural Steel

Also known as ordinary carbon steel, it has wider restrictions on carbon content, performance range, and the content of phosphorus, sulfur, and other residual elements. In China and some countries, based on delivery guarantee conditions, it is divided into three categories: Class A steel (Type A steel) guarantees mechanical properties, Class B steel (Type B steel) guarantees chemical composition, and Class C steel (Type C steel) guarantees both mechanical properties and chemical composition, commonly used in manufacturing relatively important structural components. Currently, the most widely produced and used in China is A3 steel (Type 3 steel) with a carbon content of about 0.20%, mainly used in engineering structures.

Some carbon structural steels also add trace amounts of aluminum or niobium (or other carbide-forming elements) to form nitride or carbide particles, limiting grain growth, strengthening the steel, and saving materials. In China and some countries, to meet the special requirements of professional steels, the chemical composition and properties of ordinary carbon structural steels have been adjusted, resulting in a series of professional-use carbon structural steels (such as bridge, construction, rebar, and pressure vessel steels).

High-Quality Carbon Structural Steel

Compared to ordinary carbon structural steel, high-quality carbon structural steel has lower sulfur, phosphorus, and other non-metallic impurity contents.

Depending on the carbon content and application, this type of steel is roughly divided into three categories:

• Less than 0.25% C is low carbon steel, with particular emphasis on those with carbon content below 0.10% like 08F, 08Al, etc., widely used for deep-drawing applications such as automotive parts, canning, etc. 20G is the main material for making ordinary boilers. Additionally, low carbon steel is widely used as carburizing steel in the machinery manufacturing industry.
• 0.25 to 0.60% C is medium carbon steel, mostly used in quenched and tempered states for manufacturing parts in the machinery manufacturing industry.
• Greater than 0.6% C is high carbon steel, mainly used for manufacturing springs, gears, rolls, etc. Depending on the manganese content, it can be divided into normal manganese content (0.25 to 0.8%) and higher manganese content (0.7 to 1.0% and 0.9 to 1.2%) steels. Manganese can improve steel’s hardenability, strengthen ferrite, and increase yield strength, tensile strength, and wear resistance. Typically, higher manganese steels are marked with “Mn” after the grade, such as 15Mn, 20Mn, to distinguish them from normal manganese content carbon steels.

Yield Strength

Carbon structural steels are divided into five grades based on their yield strength: Q195, Q215, Q235, Q255, Q275 (Q345 is a low-alloy steel). Each grade is further divided into A, B, C, D levels, with a maximum of four grades, some having only one. Additionally, there are differences in steelmaking deoxidation methods.

Chinese Standards for Structural Steel Profiles

Steel should preferably adopt Q235, Q345, Q355, Q390, Q420, Q460, Q345GJ, Q420GJ, Q460GJ steels, and their quality should meet the requirements of the current national standards “Carbon Structural Steel” GB/T 700, “Low-Alloy High-Strength Structural Steel” GB/T 1591, and “Steel Plate for Building Structures” GB/T 19879. The specifications, dimensions, weight, and allowable deviations of profile products such as structural steel plates, hot-rolled I-beams, channels, angles, H-beams, and steel pipes should comply with the relevant current national standards.

For welding-bearing structures, to prevent laminar tearing of steel, Z-direction steel should meet the requirements of the current national standard “Thickness Direction Performance Steel Plate” GB/T 5313.

For load-bearing structures exposed to outdoor environments with special corrosion resistance requirements or in corrosive media environments, weather-resistant structural steels of grades Q235NH, Q355NH, and Q415NH can be used, and their quality should meet the requirements of the current national standard “Weather-Resistant Structural Steel” GB/T 4171.

The quality of non-welded structural cast steel parts should comply with the current national standard “General Engineering Cast Carbon Steel Parts” GB/T 11352, and the quality of welded structural cast steel parts should comply with the current national standard “Welded Structural Cast Steel Parts” GB/T 7659.

When using other steel grades not listed in this standard, statistical analysis should be carried out in accordance with the current national standard “Unified Standard for Reliability Design of Building Structures” GB 50068, to determine their design indicators and applicable ranges.

Types of Bending Structural Steel Sections

Although PBC series profile bending machines can bend many metals, including aluminum, brass, copper, and other alloys, carbon steel bends more than any other metal. Carbon steels have various grades, each with its unique characteristics and mechanical properties. Some grades have better bending performance than others; some are easier to process; some are more wear-resistant. Engineers, steel producers, and service centers can provide advice on the most suitable metal for your steel bending application.

Carbon Steel Bending Capability

PBC series section bending machines can bend carbon steel bars, beams, channels, tees, angles, pipes, and tubes. When you have a need for bending carbon steel, PBC series profile bending machines can provide useful resources. PBC series profile bending machines have some of the world’s largest carbon steel bending equipment/PBC 700.

Carbon Steel Shape Options

There are various choices for structural steel shapes to meet your unique project requirements:

Carbon Structural Steel Angle

Carbon steel angles are hot-rolled or high-strength low-alloy steel bars shaped into a 90-degree “L” shape. The legs of the “L” can be equal or unequal. Carbon steel angles are also known as angle iron or steel angles. Angle steel structures are typically used in applications that help improve rigidity and have good resistance to bending in any direction. You’ll find carbon steel angles in heavy-duty constructions like bridges, warehouses, cable towers, and buildings.

Carbon Structural Steel Channel

Carbon structural channels refer to shapes; square C-shaped channels. Types of channels include C-purlins, which have straight backs and lips facing inward on the sides. Unistrut channels have holes or perforations to allow bolt connections. Some channels have slight ridges on the back to improve rigidity. Channels are mainly used as purlins, replacing wood in steel structures. Compared to wood purlins, structural steel channels have greater load-bearing capacity and increased rigidity without adding weight.

Carbon Structural Steel Beams

Structural steel beams include I-beams, W-beams, and H-beams. All are designed to span an area to support construction. The shape of the bean influences overall strength and weight. W or wide-flange beams have wide flanges on both sides of the web. They are the most common because they have proven abilities to withstand shear loads and bending.

Carbon Structural Steel T-Sections

Carbon steel T-sections, also known as T-beams or T-steel, are hot-rolled “T”-shaped steel bars known for their strength and durability. “T”-shapes are well-suited for large load-bearing applications, primarily used in the construction industry to reinforce concrete, wood, or other metals.

Carbon Structural Bars

Bars can come in various shapes and sizes. PBC series profile bending machines have the capability to bend round bars, square bars, and flat bars. All these shapes are solid. Square and round bars can only be bent in one direction (i.e., there’s no strong axis or weak axis to bend). PBC series section bending machines have the ability to bend all sizes of square and round bars. Flat bars can be bent in a simple manner (relative to the weak axis) and a difficult manner (relative to the strong axis). PBC can perform hard bends on flat bars of any thickness and size up to FB 2½” x 16” (that’s 2½” thick material!). PBC series profile rolling machines can easily bend flat bars of any thickness and size up to FB 4” x 22”.

Summary

In conclusion, the PBC series section bending machine stands as a versatile and indispensable tool for bending various types of carbon steel components, including rods, beams, channels, and pipes. Its unparalleled capability to handle carbon steel bending needs, coupled with its precision and efficiency, makes it a cornerstone in industrial applications. By understanding the unique properties of different grades of carbon steel and leveraging the bending capabilities of the PBC profile bending machine, engineers and manufacturers can optimize production processes, ensuring superior quality and performance in their structural steel projects.