Potential Structural And Functional Materials
In the fast growing industry, steel remains to increase its uses as a potential structural and functional materials due to its high strength, soft-magnetic properties, wear resistance and good corrosion together with comparatively low material cost. Steel has a carbon content approximately 0.29 and 0.60 %.
Steel is well known to balance strength and ductility and has a good resistance to wear. It is applied in large parts, automotive components and forging. Hence it’s not shocking that much of modern research has been focused on the impacts carbon on the mechanical properties of steel. Even though there has been a lot of research which has been carried out to examine the impact of distortion limits such as strain, strain rate and temperature on the plastic characteristic of steel there has been very narrow studies on the effects of carbon content on the mechanical properties of steel.in general as the amount of carbon content increases as the hardness of steel increases at the same time elongation decreases (Kawai, 2016, p. 483).
From the previous researches which have been conducted it has been that carbon content in steel produces a small change in the softening characteristic at the deformation temperatures which are usually above no recrystallization temperature. With the increase in amount of carbon content in steel the stress ratio parameters such as oeffective are found to be higher as compared to the pure steel without carbon content.
With the carbon content increase in steel, the microstructure is altered into the martensite and the reserved austenite, plus the solid solution solidification of the carbon element. The main aim of this research is to evaluate and analysis the impacts of carbon content on the Physical properties of steel.
The amount of carbon content has a great influence on the physical properties of steel such as; steel toughness which is inversely proportional to the amount of carbon content existing in steel. Increasing the carbon content in steel increases the hardenability of steel so as the weld of steel cools it can successfully be quenched, leading to a hard, brittle material in the heat affected areas (Davis, 2011, p. 876). Increased amount of carbon content reduces malleability and ductility in steel.
The mechanical strength and hardness of steel increases with the increase in the amount of carbon content present in steel, But the impact toughness decreases as the hardness and strength increases.
Common Mechanical Properties Of Steel Properties
Steel strength refers to the capacity of steel to endure loads inclining to elongate as conflicting to compressive strength that endures loads inclining to decrease size. In other words tensile strength opposes tension i.e. being pulled apart. While compressive strength of steel opposes compression i.e. being pulled together (Mukoyama, 2012, p. 76). The strength of steel is measured by the highest amount of stress that it can withstand when being pulled together or stretched before breaking.
Ductility refers to the extent of the degree through a steel can elongate or strain amid the start of yield and ultimate break under tensile loading as shown below. Many designers who uses steel depends on ductility for a number of phases of design such as reorganization of stress at the final limit state, fabrication process ,condensed risk of exhaustion and bolt group design (Demeri, 2013, p. 250). The figure below shows the stress strain for steel.
Fig 1: stress-strain behavior for steel.
Hardness refers to the measure of the resistance confined plastic distortion that is introduced by either mechanical abrasion or indentation. Some materials are tougher than others .Macroscopic hardness is usually described by the tough intermolecular bonds. Hardness of steel is dependent on many aspects such as elastic stiffness, strain, toughness, ductility and viscosity (Sherby, 2013, p. 117).
Most of the steel types are weldable. Nevertheless, welding includes locally melting the steel, that later cools. The process of cooling can either be slow or fast depending on the surrounding material. The susceptibility to embrittlement also relies on the alloying elements mainly, but not entirely, the carbon content. The susceptibility can be conveyed as the Carbon Equivalent Value and the different product standards for steel standards given expressions for establishing this value.
Fracture toughness refers to the mechanical property of steel which describes the ability of steel to resist fracture, it is considered to be one of the most essential property of steel regarding to design specification of various components. The fracture toughness of steel is established from stress intensity factor at which cracks starts to develop in steel. In most cases the fracture toughness is considered as a qualitative method of showing the resistance of steel to brittle.
Classification Of Steel Depending On The Carbon Content.
Steel is classified into three categories as shown below.
- Plain carbon steel
- Mild carbon steel
- High carbon steel
Plain Carbon Steel
This category of steel are usually iron which contains less than 1 percent carbon content, together with small amount of phosphorus, Silicon, Manganese and sulphur. The weldability and other mechanical properties of this steel are major products of carbon content, even if residual elements and alloying do have a minor influence (The Minerals, 2015, p. 43).
The plain carbon steel is fabricated into a wide arrange of products which include: car bodies, structural beams, cans and kitchen appliances.
Low Carbon Steel.
This type of steel contains up to 0.25% carbon respondent to heat treatment as an improvement in the ductility but the carbon content that is contained in this type of steel has no effect in relation to its strength. Its strength is generally low due to the low amount of carbon content (Woolman, 2014, p. 371). It is easy to bend and work with but it is not encouraged to be used as structural steel due to its low strength.
Mild Carbon Steel
This type of steel contains carbon content ranging from 0.25 to 0.705 which improves in the machinability by heat treatment. This type of steel is mainly adapted in forging or machining where surface hardening is required. As the name suggest this type of steel is a low-cost steel which is easy to shape. The strength and hardness of this type of steel can be improved by the additional of carbon content (Pharma, 2015, p. 169). The mild carbon steel is used for production of gears, bolts, axles, studs and other machine parts due its strength.
High Carbon Steel
Usually the high carbon steel contains carbon content of o.6 to 1.0% together with manganese contents ranging from 0.30 to 0.9%.The high carbon content present makes the steel to be very hard unfortunately the high amount of carbon content also makes steel to be brittle and the level of ductility reduces as compared to the mild steel. The high and medium carbon steel are widely used in many common applications. Adding the amount of carbon as the major alloy for higher hardness and strength is the best approach to enhance the performance of steel. Nevertheless, the elevated amount of carbon content has negative impacts to steel such as reduced ductility and weldability (Mukoyama, 2012, p. 77).
The high carbon steel has wide applications such as; rail steels, forging grades, spring steels, pre-stressed concrete, wear resistance, wire rope and the high strength bars.
To enhance the functionality of steel in this uses it is advisable to maximise hardness and strength by increasing the amount of carbon content present. The limiting factor to addition of carbon content will vary depending on the nature of application. For bar products and forging steel, it may be weldability and toughness. For the case of high strength wire the limiting factor to the addition of carbon content can be eutectoic carbon level, more than which the presence of grain edge carbides will greatly reduce draw ability (Morral, 2013, p. 67).
Potential Structural And Functional Materials