Carbon Steel vs Stainless Steel: Which is Better

Steel is playing vital role in the infrastructure of any country and its prosperity which signifies steel as a backbone of economy. Steel has revolutionized the modern world in the field of construction, medical, food processing and in marine applications. Steels are classified into two main categories; carbon steel and stainless steels. Stainless steel has at least 10.5 wt. % of chromium whereas it is not compulsory for carbon steel. If stainless steel is compared with low carbon steel, a massive change in mechanical properties and corrosion resistance will be witnessed. This article is written to compare stainless steel and carbon steel on the grounds of composition, mechanical properties, physical properties and applications which would develop an understanding in the reader to make better choice of material for desired applications.  

Chemical Composition of Carbon Steel

Carbon steel is mainly composed of ~ 10.5 wt.% of alloying element and base metal is iron. Carbon is added in the range of 0.12-2 wt.% along with other alloying elements which has massive impact on mechanical properties as well as physical properties. Carbon steel area on phase diagram is indicated by two red dashed lines.

Concentration of carbon present in the alloy can translate the hardness of an alloy [1]. Carbon steel is divided into four main classes on the basis of carbon which are as follow;

Composition of carbon steel from ultra-high carbon steel to low carbon steel is given in following table;

What is carbon steel used for

Carbon steels is a ferrous alloy where carbon derives the main properties in an alloy. By increasing or reducing the carbon content, has direct impact on hardness of the material. Its properties are further improved by different heat treatments which makes it a suitable candidate for many applications and also available in different semi-finished forms in markets for further processing such as;

Carbon steel block

Billets or blocks of carbon steel are formed by casting, forging and rolling. In case of casting, molten carbon steel is poured in the block die and after solidification, carbon steel block is retrieved from the die and forwarded for further processing [3]. As in some applications, cast structure is not required as it is non-homogenous so further processing is recommended. Rolling and forging are applied as per desired application [4].

Carbon steel wire

Common wire fabrication process of carbon steels is wire drawing. Carbon steel wires are used for the manufacturing of springs, nuts and bolts, ropes, mesh and cables. Carbon steel wires are versatile and possess good mechanical properties along with cost effectiveness.

Carbon steel bars

Applications of carbon steel semi-finished product is found in automotive, tools, wind-engine, petrochemical plants and metallurgical machinery [6]. Is found in hot rolled, cold drawn, forged condition in round, square and hexagonal rode shapes. Usually surface is black and rough after heat treatment.

What is High Carbon Steel

High carbon steel contains carbon content in the range of 1.6 to 2.0 wt. %. As it has higher carbon content which results in higher hardness and tensile strength by compromising the ductility and forming properties. Moreover, it is used in tool making, blades, ball bearings, knives.

Stainless steel carbon content

Stainless steel has at least 10.5 wt. % chromium along with less than 1.2 wt. % carbon content. In stainless steel, carbon is not only the alloying elements which dictates the mechanical properties [8]. Other alloying elements such as nickel, molybdenum, niobium, titanium and manganese are also added. Variation of alloying elements in the composition of stainless-steel results in martensitic stainless steel, austenitic stainless steel, and precipitation hardened steel, duplex steel and ferrite stainless steel.

What is the Difference Between Carbon Steel and Stainless Steel

It is established that different alloying elements along with different concentration are used in stainless steel and carbon steel. Stainless steel is stainless as name suggests and on the other hand, carbon steel has carbon as main alloying element which dedicates mechanical properties of the steel. Here, is a comparison of both alloys on the basis of weight, corrosion resistance, cost and mechanical properties.

Weight

Weight of the material highly dependent on the density of the material which is altered by the alloying elements. Mainly density depends on the base element of an alloy. In case of carbon steel and stainless steel, base metal is iron which is same. Alloying elements of stainless steels are high in concentration as a result more weight is contributed by stainless steel alloying elements. Density of carbon steel is 7.85 g/cm³ whereas stainless steel has 7.75 to 8.05 g/cm³. Densities of both alloys translated that stainless steel is heavier than carbon steel.

Corrosion resistant

In stainless steel, minimum of 10.5 wt. % chromium is added which creates a passive layer on the surface and protect it from further oxidation. As both alloys contain iron as base metal, iron has tendency to form its oxides when comes in contact with air. Stainless steel is tailored to reduce iron oxidation by adding chromium. Carbon steel has inferior corrosion resistance than stainless steel. Stainless steel is resistant to weak and strong acids such as organic acids, mineral acids (phosphoric acids), nitric acid and sulfuric acid at room temperature. On contrary, carbon steel is inferior to stainless steel in the presence of weak, mild and strong acids.

Is carbon brittle

Brittleness of the carbon steel is entirely depending on the carbon content and heat treatment. Higher the carbon content, low will be the ductility. High carbon steel is brittle and hard due to the presence of high carbon content which is 0.6-1.5 wt. %.

Is carbon ductile

Carbon can’t be transformed into wires whereas carbon steels can be drawn into wires. As, it is already mentioned that four classes of carbon steels are present. Low carbon steel exhibit good ductility and has good weldability and formability. As low carbon steel has lower carbon content than high carbon steel which is 0.05-0.32 wt. %.

Is stainless steel strong

Yes, stainless steel is strong. As it is mentioned that stainless steel have five different types and you will comprehend the idea of strength in a better way if all the types will be listed here with maximum and minimum tensile strength.  Precipitation hardened stainless steel has tensile strength in the range of 600 to 1500 MPa. Austenitic and martensitic stainless steel has strength of 200-1000 MPa and 500-2000 MPa, respectively. Ferrite and duplex stainless steel have lowest tensile strengths among stainless steel grades which is 400-800 MPa and 550-800 MPa, correspondingly.

Is carbon steel stronger than stainless steel

A range of the tensile strength of carbon steel can be given but it won’t give you depth knowledge. So, in order to inculcate the basic idea of this article which is to develop a better understanding of carbon and stainless steel in the reader. Low carbon steel has tensile strength in the range of 270-580 MPa and medium carbon steel has 485-760 MPa, respectively. High carbon steel exhibit higher tensile strength among carbon steel which is 550-2100 MPa. High carbon steel is stronger than many stainless steels and also many stainless steels exhibit superior tensile strengths than many carbon steels. It entirely depends on the alloying elements, heat treatment and fabrication route. It can’t be said that stainless steel is better than carbon steel or vice versa.

How hard is carbon steel

As the carbon content increases, hardness of the carbon steel increases. High carbon steel is relatively hardest, it has 150-300 HB [23]. On the other hand, medium and low carbon steel has relatively lower hardness which is 170-300 HB [24] and 120-210 HB, respectively.

Is stainless steel harder than carbon steel

Hardness of stainless steel varies among different types of stainless steel. Austenitic stainless steel and martensitic stainless steel have 140-230 HB [26] and 200-500 HB, respectively.  Ferrite and precipitation hardened stainless steel have 150 -210 HB [27] and 240-450 HB, respectively. Typically hardness lies in the range of 140-500 HB in case of stainless steel whereas in carbon steels, range of hardness is 120-300 HB. From facts, it is established that stainless steel is harder than carbon steel.

Cost

Carbon steel is more affordable than stainless steel due to the alloying elements and production cost. Price of stainless steel is approximately 1.5-5 $ per pound and estimated price of carbon steel is 0.25-0.80 $. As the price varies in different grades of stainless steel and carbon steel, so a range is given. Price can also be varied on need and demand basis from place to place. Stainless steel is expensive than carbon steel but low maintenance and high durability can save the cost in longer run.

Carbon steel vs stainless steel properties

Comparison table of carbon steel and stainless-steel properties

Is carbon steel better than stainless steel

Carbon is better than steel or not, depends on the application. If high corrosion resistance is required along with good combination of mechanical properties than stainless steel is better than carbon steel. On contrary, budget is low and less expensive material is required and doesn’t require good corrosion resistance then carbon steel is better than stainless steel.

Stainless vs carbon steel knife

In stainless steel and carbon applications, steel knives are very important. Stainless steel knives are highly corrosion resistance and required low maintenance as compared to carbon steel. Carbon steel knives have tendency to rust easily so special cleaning is required. Moreover, edge retention of the knife is better in carbon steel as compared to stainless steel. Sharpening of stainless-steel knife edges is critical and need specialized equipment whereas carbon steel knives are easier to sharp. Toughness and sustainability of stainless-steel knives are better than carbon steel.

Carbon steel pan vs stainless

Conductivity of heat and uniform heat distribution of carbon steel pan is better than stainless steel pans. Cleaning and maintenance of carbon steel pan is difficult than stainless steel pans. Steel pans are heavier than carbon steel pans but lighter than cast iron pans. Carbon steel pan has tendency to react with acids and impart metallic taste to the cooked food which is not the case with stainless steel.

Carbon steel vs stainless steel wok

Seasoning of carbon steel wok develop non-stick property. High maintenance is required to keep it free from rust and to keep nonstick property intact. Carbon steel woks are less durable as compared to stainless steel wok. Stainless steel woks do not possess nonstick property.

How to get rust off carbon steel

Multiple methods are utilized to clean up the rust which includes; vinegar soaking, scrubbing, neutralizing acid, rinsing and drying and by applying oil or seasoning.

Who is better for machining and welding

Carbon steel has better machining and welding than stainless steel. Stainless steel has higher hardness, less thermal conductivity makes it a challenging material for machining. Also, sensitization of stainless steel is a common problem in welding which requires higher attention while welding.

Conclusion

Both alloys have their own advantages and disadvantages. Stainless steel has high chromium content which makes it stainless as compared to carbon steel. In carbon steel, carbon impart the mechanical properties whereas in stainless steel, other alloying elements such as molybdenum, nickel and manganese participate in influencing the mechanical properties. While choosing the material for specific application, budget must be kept in mind so carbon steel is more affordable than stainless steel. To make correct decision about the selection of material regarding any application, consult our experts, Toufa consultancy will not only save your time but also will be light on your pocket as for as finances and quality concern.

FAQs 

Is 4140 steel stainless?

No, 4140 is not a stainless steel but a low alloy steel of chromium and molybdenum.

Do carbon steel pans rust?

Yes, if proper care (seasoning and cleaning) is not taken than carbon steel can rust.

stainless steel knives pros and cons

Stainless steel knives are durable, corrosion resistance, low maintenance but low edge retention and might need specialized equipment for sharpening.