Steel pipes are an indispensable basic material in engineering projects such as construction, machinery manufacturing, and oil pipelines. However, faced with the wide variety of steel pipe products on the market, many buyers and engineers are often confused: what exactly is the difference between mild steel pipe and carbon steel pipe? Mild steel pipes and carbon steel pipes differ significantly in several dimensions, including chemical composition, properties, applications, cost, weldability, and corrosion resistance.

Mild Steel Pipe Meaning

Mild steel pipes ( MS pipe full form) , also known as carbon steel pipes, have a lower carbon content, typically between 0.05% and 0.25%. Compared to high-carbon steel, mild steel pipes have better ductility and are easier to process. Due to their excellent weldability, machinability, and economy, mild steel pipes are widely used in structural and industrial fields.

 

Mild steel pipes properties:

Low carbon content (0.05%–0.25%);

High ductility and forgeability;

Excellent weldability;

Medium tensile strength;

Susceptible to corrosion without additional coating or galvanizing;

Suitable for large-scale applications, high cost-effectiveness.

 

Carbon Steel Pipe Meaning

Carbon steel pipes ( CS pipe full form) have a higher carbon content (0.25% to 2.0%), making them stronger and more durable than ordinary mild steel pipes. The higher carbon content increases hardness and wear resistance but reduces ductility. Carbon steel pipes are commonly used in high-pressure applications, oil and gas pipelines, and heavy industrial environments.

 

Carbon steel pipes properties:

Higher carbon content (0.25%–2.0%);

Higher strength and hardness;

Poorer flexibility and weldability compared to ordinary low-carbon steel;

Higher wear resistance and impact resistance;

More prone to rust and corrosion without protective coating;

Suitable for high-pressure and structural applications.

Carbon Steel vs. Mild Steel

Property	Carbon steel	Mild steel
Strength	Higher strength	Lower strength
Corrosion resistance	Low ( but slightly better than mild steel)	Low ( needs coating )
Ductility	Less ductile	Highly ductile
Weldability	Harder to weld	Easy to weld
Machinability	Harder to machine	Easier to machine
Price	More expensive	Less expensive

Mild Steel Pipe vs. Carbon Steel Pipe

1. Differences in Chemical Composition

Carbon Content: Low-carbon steel generally has a carbon content below 0.25%; medium-carbon steel generally has a carbon content between 0.25% and 0.60%; high-carbon steel generally has a carbon content above 0.60%.

Besides carbon (C) and certain amounts of silicon (Si) (generally not exceeding 0.40%) and manganese (Mn) (generally not exceeding 0.80%, with a maximum of 1.20%) used for deoxidation, steel does not contain other alloying elements (except for residual elements).

Generally, steel with a carbon content below 0.02% is called wrought iron, steel with a carbon content between 2.11% and 4.3% is called pig iron, and steel is defined as steel in between.

Mild steel has the lowest carbon content among carbon steels, possessing the best machinability and weldability, and is therefore widely used in construction and piping systems.

2. Application Differences

Main uses of mild steel pipes:

Building structures (angle steel, channel steel, rectangular tubes, round tubes)

Water, gas, and low-pressure oil transportation pipelines

Fire protection pipelines, HVAC pipelines

Automotive manufacturing (body panels, stamped parts)

Machinery and appliance housings

Parts that can be carburized (e.g., sprockets, bushings, shafts)

Main uses of medium-carbon/high-carbon steel pipes:

Suitable for applications requiring high load-bearing capacity and wear resistance:

Railway tracks

Prestressed steel

Wire ropes

Knives, saw blades

Gears, chains

High-pressure, high-temperature pipelines (e.g., ASTM A106)

3. Cost Differences

Carbon steel contains approximately 0.05%–1.70% carbon (by weight). Increasing the carbon content in steel can enhance its strength and is considered the most economical way to improve steel strength. However, increasing the carbon content also leads to increased brittleness and decreased ductility.

Therefore, the carbon content must be balanced to obtain the desired additional properties of the steel. High-carbon steel has a carbon content between 0.3% and 1.70%, while low-carbon steel has a carbon content between 0.05% and 0.15%.

Mild steel pipes are among the lowest-cost and most in-demand steels, making them widely used in the construction industry, fire protection systems, and general transportation applications.

 

4. Differences in Strength and Durability

Carbon steel pipes, due to their higher carbon content, have higher strength and hardness, making them ideal for heavy industrial applications.

Mild steel pipes, on the other hand, have better flexibility and ductility, making them easier to process and install.

5. Differences in Corrosion Resistance

Neither low-carbon nor carbon steel pipes are corrosion-resistant and must be protected with coatings or galvanizing.

Common corrosion-resistant methods include:

Black varnish

Hot-dip galvanizing (HDG)

Cold galvanizing (GI)

Epoxy coating

6. Differences in Weldability and Machinability

Due to their lower carbon content, mild steel pipes are easier to weld and process, making them suitable for projects requiring frequent modifications.

Although carbon steel pipes have high strength, they are difficult to weld and require special welding processes to avoid embrittlement.

Things to Consider When choosing Carbon Steel Pipe Raw Materials

1. Is the Machinability of Carbon Steel Good?

There are many types of carbon steel. Some types of carbon steel are easy to machine, but there are also types of carbon steel that are difficult to machine. Mild steels have good machinability, such as C1010 and C1018. Carbon steels with higher carbon content can also be processed easily, but sulfur is added to the chemical composition, such as C1141 and C1144. C1045 has a higher carbon content but no other elements to aid in its processing, making it a poor choice if processing is required.

2. Is Carbon Steel Weldable?

Certain types of carbon steel are weldable very well. However, there are several factors to consider when choosing carbon steel to weld. First, carbon steels suitable for machining, such as C1141 and C1144, are generally not weldable. Adding sulfur to these carbon steels can cause weld solidification cracks. Mild steels such as C1018 and A36 would be better choices as they are easy to weld. Higher carbon steels such as C1045 can also be used, but may require preheating or post-weld heat treatment.

3. What are the Strength Requirements of Carbon Steel?

Mild steels tend to lack tensile strength compared to other carbon steels. If high strength is required, these mild steels should be avoided. Carbon steel with a higher carbon content provides greater strength and hardness than carbon steel with a lower carbon content. For example, the strength and hardness of C1045 is higher than that of C1008. However, there are alternatives to mild steel: high-strength low-alloy steel (HSLA). HSLA is a low-carbon base steel specifically designed to maintain formability while maintaining greater strength.

4. Does Carbon Steel Need Good Formability?

The category of carbon steel is so broad that there are many different combinations of mechanical properties. If ductility is required, lower carbon grades such as C1008 and C1010 should be considered. As a rule of thumb, mild steel is easier to form than high carbon steel.

5. Is It Easy to Heat Treat Carbon Steel?

Carbon steels with greater than 0.30% carbon content can be easily heat treated, such as C1045 and C1141. Another option is steel with just over 0.20% carbon. These carbon steels can have trace amounts of other elements added to improve their hardenability, such as A36. Low carbon steel, that is, steel with a carbon content of less than 0.20%, is not easy to heat treat.

6. Does Carbon Steel Have Good Corrosion Resistance?

Carbon steel's corrosion resistance is not very good. They are primarily composed of iron that can oxidize and form rust. If enough corrosion-resistant elements, such as chromium, are not added to the chemical composition, the corrosion resistance will not be very good. Choosing galvanized or electroplated carbon steel is a viable option to prevent corrosion. Alternatively, adding oil or paint to the surface of carbon steel is a great way to help prevent iron from oxidizing.

7. Application Fields

Understanding the common applications of different grades of carbon steel can help you choose the right carbon steel for your application. Here are some typical uses:
A36/44W: Automotive parts, cams, fixtures, fuel tanks, forgings, structural applications such as buildings or bridges.
C1008, C1010, C1018: Mechanical parts, tie rods, lower strength structural applications, mounting plates and brackets.
C1045: Bolts, gears, crankshafts, cylinder shafts, die forgings, and applications requiring higher strength or higher hardness than C1008 or C1010.
C1141 and C1144: Studs, bolts, shafts, tie rods and similar applications to C1045.

FAQ

1. Which is stronger: mild steel or carbon steel?

Higher-carbon steel is stronger, but mild steel is more ductile and easier to weld.

 

2. Is mild steel pipe suitable for water or HVAC systems?

Yes. Mild steel (e.g., ASTM A53 / EN 10219) is widely used in water supply, fire-fighting, HVAC, and structural works.

 

3. Does carbon steel pipe rust easily?

Yes. Both mild steel and higher-carbon steel require coating or galvanizing to prevent corrosion.

 

Summary

In summary, while both mild steel pipes and carbon steel pipes belong to the carbon steel material family, their roles in engineering projects differ significantly due to variations in carbon content, strength, processability, and application scenarios. Low-carbon steel is more suitable for building construction and general piping systems, while high-carbon steel is commonly used in high-strength and wear-resistant applications. Understanding these differences not only helps avoid project losses caused by incorrect material selection but also assists procurement personnel in finding the optimal balance between budget, performance, and delivery time.

Read more: Difference between seamless pipe and seam pipe  or How long can mild steel pipes last?