Chemical composition table SCM440 steel

1. SCM440 steel classification
a. Classification of steel according to carbon content:
Carbon (C) is one of the important factors determining the hardness of SCM440 steel. The higher the carbon content of the steel, the harder, brittle and more fragile the workpiece is. The lower the carbon content of the steel, the easier it is to shape but does not guarantee hardness. Therefore, people rely on this element to classify SCM440 steel as follows:
- Low carbon steel: Carbon content ≤ 0.25% has high toughness but low strength and stiffness, heat treatment effect + tempering is not high. Used as building structures, sheets for cold stamping.
- Medium carbon steel: Carbon content of 0.3% - 0.5% has high strength, stiffness, ductility and toughness although not the highest, has good tempering effect. Used mainly for machine parts subjected to static loads and high impact.
- Carbon steel is relatively high: Carbon content of 0.55% - 0.65% with the advantage of having a relatively high hardness, highest elastic limit, used as elastic parts.
- High carbon steel: Carbon content ≥ 0.7% with the advantage of having high hardness and wear resistance, used as a tool such as knives, stamping dies, ...
b. Classification by the content of metal elements:
Steel is made of many different alloy groups, depending on the chemical composition of the elements, which gives products suitable for their individual use.
- Low alloy steel: The total content of other metal elements ≤ 2.5%;
- Medium alloy steel: Total content of other metal elements 2.5% - 10%;
- High alloy steel: Total content of other metal elements> 10%.
2. Chemical composition SCM440
According to the above-mentioned properties, how does the SCM440 steel chemical composition include the elements and their content? And SCM440 steel is classified into any of the above steel groups

SCM440 steel is classified into steel with medium carbon content so SCM440 steel has medium hardness. In addition, SCM440 steel also possesses Cr - Mo content, which has high deformation resistance and abrasion resistance. With these advantages, SCM440 steel is widely used in industries such as gears, gear bars, transmission shafts, steel rolling shafts, anchor bolts, ...
3. Effect of elements in the chemical composition SCM440
a. Chemical composition of steel SCM440 - Carbon (C)
Carbon is the most important element, deciding primarily on the organization, properties (mechanical properties) and use of steel. Carbon has the most effect on HB hardness. Quantitatively, it was found that an increase of 0.10% C HB hardness would increase by about 25 units.
The carbon content also affects the cutting properties of steel. In general, the harder the steel, the harder it is to cut, so the high-carbon steel has poor cutting performance. But too soft and ductile steel also makes it difficult to cut, so low-carbon steel also has poor cutting properties.
b. Chemical composition of steel SCM440 - Silicon (Si)
Silicon is added to steel in the form of silicon fero to completely de-oxidize the steel in a liquid state. Like manganese, silicon dissolved in ferrite also enhances strength and hardness, which increases the mechanical properties of steel.
c. Chemical composition of steel SCM440 - Manganese (Mn)
Manganese is added to steel in the form of manganese fero to de-oxidize the steel liquid to eliminate very harmful FeO. Manganese has a good influence on mechanical properties, when dissolved into ferrite, it increases the strength and hardness thus increasing the mechanical properties of steel. In addition, manganese also works to reduce the harmful effects of sulfur.
d. Chemical composition of steel SCM440 - Phosphorus (P)
As the element has the ability to dissolve into ferrite (up to 1.2% in pure alloy Fe - C, also in this soluble limit steel sharply decreases) and greatly dislocates the crystal lattices to increase brittleness. , when the phosphorus content exceeds the solubility limit, the steel becomes hard and brittle. With only 0.10% dissolved phosphorus, ferrite will become brittle. However, phosphorus is a very strong (unevenly distributed) elemental element, so to avoid brittleness, the phosphorus in steel must be less than 0.05%. ).
e. Chemical composition of steel SCM440 - Sulfur (S)
Unlike phosphorus, sulfur is completely insoluble in Fe and forms FeS compounds. The same crystal (Fe + FeS) forms at low temperatures (988 ° C), the final crystallization is therefore located at the grain border; When the steel is heated for rolling and drawing (usually at 1100 - 1200 ° C) the border is melted, making the steel vulnerable to fracture, such as very brittle steel.
f. Chemical composition of steel SCM440 - Chrom (Cr)
Chromium is a common chemical element for alloying, which is an average carbide generating element. Chromium can dissolve in ferrite, when the chromium content is high, it will combine with carbon to create alloy cementits (Fe, Cr) and Cr7C3 and Cr23C6 carbides, these carbides raise the temperature, prevent the raised crystal. Chromium increases synthesis properties, it also has the effect of improving endurance at high temperatures because it produces fine small carbides when ram is secreted at 2500 ° C. In addition, Chromium also increases the anti-oxidant properties by creating Cr2O3 very durable.
g. Chemical composition of steel SCM440 - Molipden (Mo)
Additive of molybdenum added steel will increase local wear resistance and better crack wear. Molipden helps combat chloride damage. The higher the amount of molybdenum (steel grades up to 6%), the higher the level of chloride tolerance.
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