Table of Contents

What is Carbon Steel?

Carbon steel is an alloy composed of steel and up to 2.0% carbon by weight. Steel is an iron alloy and typically contains trace amounts of other elements such as manganese and silicon [1]. Carbon steel can be further categorized by the amount of carbon present in the alloy and is broken into the categories low, medium, or high. Low carbon steel contains 0.04%-0.30%, medium is 0.31%-0.60%, and high is 0.61%-1.50% [1]. The behavior of iron with a main alloying element of carbon can be illustrated by the phase diagram in Figure 1. Increasing amounts of carbon present in the iron alloy reinforce the strength of the steel but make it very difficult to physically alter the material. This means that high carbon steel is the strongest carbon steel but its also the most difficult to bend, cut, or weld [1]. Structurally, carbon steel is characterized by it's increased strength compared to normal steel due to the reinforcement of the crystal lattice by the addition of carbon [2]. Carbon steel however is more prone to rust or corrosion since the alloy is still primarily iron and is not reinforced with chromium like stainless steel is [2].

Figure 1: Phase Diagram of Iron and Carbon [9]

Carbon Steel Pipes

Pipes are essential components of industrial equipment and operations as they are needed to transport materials safely and efficiently throughout a plant. Many factors need to be considered when determining what type of pipe is suitable for the job such as what temperatures and pressures the pipe will be subject to or what kind of material the pipe will be transporting. The increased strength of carbon steel makes it a good choice for piping that will be under a lot of force. Industries that often contain carbon steel piping include shipping, infrastructure, and distillers. Carbon steel also has good shock, weather, and pressure resistance making it a durable choice for harsher conditions [3]. Further advantages and disadvantages can be highlighted in the table below.

Advantages

Disadvantages

Can withstand lots of force and pressure [3]
- Low carbon steel has a tensile strength of 65 300 psi and a yield strength of 47 900 psi
- High carbon steel has a tensile strength of 140 000 psi and a yield strength of 84 800 psi [10]
Can be used in situations where there are large changes in pressure or temperature [4]
Shock and weather resistance [3]
Low cost to manufacture and purchase
Due to its high resistance to force, the piping wall can be thinner thus saving more material [4]

Due to the presence of a strong carbon lattice, carbon steel is very difficult to bend and weld
Since carbon steel cannot bend very well it is prone to snapping
More prone to rust and corrosion due to a lack of chromium [2]

Industry Applications

The numerous advantages of carbon steel make it extremely useful for various industries and purposes. Carbon steels resistance to shock and vibrations makes it a good use for piping under roadways and can be used to construct water mains, gas lines, and sewage pipes. Carbon steel can also be used as a viable option for high pressure fluid transportation and the added recyclability makes it a good choice for industrial companies looking to reduce their environmental waste [4]. The high strength of carbon steel makes it a common pipe in heavy duty industries such as chemical fertilization, shipping, and distillation [3]. Carbon steel pipes are often connected to each other through threaded fittings. Threaded fittings are good fasteners for carbon steel as they are resistant to high pressure and violent conditions. Although they have their advantages, threaded fittings can be more prone to corrosion [5].

Figure 2: Carbon Steel Pipes Used in Condenser Water System [8]

Sizing

*Figure 3: Carbon Steel Pipe Sizing Chart [6]*

Suppliers

Along with being able to buy carbon steel piping from hardware suppliers such as Home Depot or Rona, there are various suppliers available to Ontario who can manufacture pipes made for the consumer's specific requests. The following are a few of the big suppliers for carbon steel pipes to Ontario.

Continental Steel and Tube Co.
Bassett Industries Inc.
Infra-Metals Co.
Samuel Son & Co Inc.
National Tube Supply [7]

References

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Faculty Advisor: Mary Robinson

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