Cast iron from steel than differs visually?

A low-aware person believes that the main constructional material of our time is iron. The person who understands knows that the word "iron" refers to iron-carbon alloys - steel and cast iron. It would seem that two absolutely different materials and they are very easy to distinguish. However, given the wide range of their types and brands, the fine line of difference in the chemical composition of some of them is difficult to determine. It is important to have additional skills in order to know the answer to the question: what is the difference between cast iron and steel?

Cast iron

The alloy containing iron, carbon in the amount of 2.14-6.67, sulfur, phosphorus, manganese, silicon and other additives is called cast iron. The history of smelting began in the Iron Age. Important structural material, the basis of metallurgy and the entire steelmaking industry.

Characteristics:

1. Rough, gray matte color.
2. Melting at 1000-1600 ° C, depending on the composition (for industrials on average - 1000-1200 ° C, white and pig iron melts at higher temperatures).
3. Density: 7200-7600 kg / m ³ .
4. Specific heat capacity: 540 J / (kg˚С).
5. High hardness: 400-650НВ.
6. Low ductility, very crumbled when exposed to pressure; The highest values of the relative elongation are malleable high-strength cast iron δ = 6-12%.
7. Low strength: 100-200 MPa, for malleable its value reaches 300-370 MPa, for some high-strength grades - 600-800 MPa.
8. It is modeled by heat treatment, but rarely and with great caution, since it is characterized by a cracking process.
9. It is doped with the aid of auxiliary chemical elements, but a significant degree of doping further complicates the processing processes.
10. Characterized by satisfactory weldability, good machinability cutting, excellent casting properties. Forging and stamping is not allowed.
11. Good wear resistance and corrosion resistance.

Cast iron - a material for body parts, blocks, knots of machines, made by casting. It is the main charge component for steel smelting.

Steel

Iron-carbon alloy, containing carbon in an amount not more than 2.14% and iron - at least 45%, is called steel. Its main features:

1. Smooth, has a silvery color with a characteristic reflection.
2. Melting is within 1450 ° C.
3. Density is from 7,700 to 7,900 kg / m ³ .
4. Heat capacity at room temperature: 462 J / (kg˚С).
5. Low hardness, on the average 120-250 НВ.
6. Excellent plasticity: the coefficient of relative elongation δ for different brands varies within the range of 5-35%, for the majority - δ≥20-40%.
7. The average values of the tensile strength for structural materials are 300-450 MPa; For especially durable alloyed - 600-800 MPa.
8. It is amenable to correction of properties by means of thermal and chemical thermal treatment.
9. It is actively alloyed with various chemical elements in order to change the properties and purpose.
10. Qualitatively high parameters of weldability, machinability of pressure and cutting.
11. Characterized by low corrosion resistance.

Steel is the main structural alloy in modern metallurgy, machine building, instrument making and engineering.

Determine the origin by the type of part

Having considered the detailed characteristics of these alloys, it is possible to confidently use the knowledge that iron is different from steel. Having before itself a metal object, doubting its origin, it is rational to immediately recall the main distinctive technological properties. So, cast iron is the foundry material. It produces simple utensils, massive pipes, machine housings, engines, large objects of a simple configuration. From steel parts are made of all sizes and complexity, because for this, forging, stamping, drawing, rolling and other methods of metal working with pressure are used. Thus, if there is a question about the origin of the armature, there can be no doubt that it is steel. If the origin of the massive cauldron is of interest, it is cast iron. If it is necessary to find out what the motor or crankshaft housing is made of - other variants of recognition should be resorted to, since both variants are possible.

Color features and analysis of brittleness

In order to know how to distinguish cast iron from steel to the eye, you need to remember the main visual differences. Cast iron is characterized by a matt gray color and a rougher outer texture. Steel is characterized by a special silvery shiny shade and minimal roughness for it.

Also an important knowledge of how to distinguish cast iron from steel visually is information about the plasticity of these materials. If the investigated blanks or metal objects do not have a serious value, you can try them for strength and plasticity by applying shock force. Fragile cast iron crumbles into pieces, while steel only deforms. With more severe loads aimed at crushing, the crumbs of cast iron will turn out to be of a small variety in shape, and pieces of steel - large, regular configuration.

Cut and Drill

How to distinguish cast iron from steel at home? It is necessary to get small dust or shavings from it. Since the steel has a high plasticity, then its shavings are also crooked. Cast iron is crumbling, while drilling, a small shaving of the fracture is formed along with the dust.

To obtain dust, you can use a file or a rasp and slightly sharpen the edge of the part of interest. The resulting fine-grained chips should be examined on a hand or a white sheet of paper. Cast iron contains carbon in large quantities in the form of graphite inclusions. Therefore, when rubbing its dust, a black graphite "trace" remains. In steels, carbon is in a bound state, so the mechanical effect on the dust does not give any visible results.

Heat and spark

How to distinguish cast iron from steel? It is necessary to operate with the necessary equipment and a small margin of patience.

In the first case, you can resort to heating, for example, using a blowtorch, wearing initially a special protective clothing and observing the safety rules in work. The temperature should be raised before the beginning of the melting of the metal. It has already been said that the melting point of cast iron is higher than that of steel. However, this applies mainly to white and pig iron. Regarding all industrial brands - they contain carbon in an amount of no more than 4.3% and melt already at 1000-1200 ° C. Thus, it can be melted much faster.

The cognitive method of obtaining information on whether iron is different from steel is the use of an experimental sample on a grinding machine or under a sharp grinding wheel. The analysis is carried out according to the characteristics of sparks. Cast iron is characterized by soft sparks of red color, and for steel - bright blinding short rays with a white-yellow hue.

How it sounds

An interesting feature is how to distinguish cast iron from steel by sound. These two alloys sound different. It is not necessary to produce musical accompaniment on existing experimental objects. But it is necessary to have both samples or have an experienced hearing in this matter. Steel is characterized by a higher density, which affects its sound. When you hit it with a metallic object, the sound is much more sonorous than in the same situation with cast iron.

In order to know, iron from steel than differs, it is necessary to have a little knowledge about these materials and a certain experience. After all, an experienced professional in the field of forging, grinding, milling, drilling, turning, heat treatment or welding, a metallurgist or technician easily distinguishes them, assessing only visually or to the touch.