The Hidden Heroes: How Elements Shape the Steel Property

Different grades of steel are produced by precisely controlling the addition of various elements during the steelmaking process to enhance the performance of steel and meet the needs of different industrial applications. This article will explore in detail how these elements affect the properties of steel and analyze their applications in actual production.

Elements During the Steelmaking

Hydrogen (H): Hydrogen is extremely detrimental to steel as it can cause hydrogen embrittlement and white spot defects. In solid steel, hydrogen has a very low solubility and dissolves in the molten steel at high temperatures. During cooling, it fails to escape in time, leading to the formation of high-pressure micro-pores within the material, which significantly reduces the plasticity, toughness, and fatigue strength of steel. In severe cases, it can even cause cracks and brittle fractures. Hydrogen embrittlement is mainly seen in martensitic steels and is less prominent in ferritic steels, generally increasing with hardness and carbon content. Despite this, hydrogen can improve the magnetic permeability of steel, but it also increases the coercive force and core losses.

Boron (B): The primary role of boron is to increase the hardenability of steel, thereby saving the use of more expensive metals such as nickel, chromium, and molybdenum. The content of boron is usually controlled between 0.001% and 0.005%, replacing a certain proportion of nickel, chromium, or molybdenum. However, boron cannot completely replace molybdenum, as molybdenum can prevent or reduce temper brittleness, while boron may slightly promote this brittleness. Adding boron to medium carbon steel can significantly improve the tempering performance of thick steel plates, allowing 40B and 40MnB steels to replace 40Cr steel, and 20Mn2TiB steel to replace 20CrMnTi carburized steel. However the effect of boron weakens with the increase of carbon content in steel.

Carbon (C): Carbon is the main component next to iron and directly affects the strength, plasticity, toughness, and weldability of steel. As the carbon content increases, the strength and hardness of the steel increase, while the plasticity and toughness decrease. A high carbon content can also reduce the weldability and atmospheric corrosion resistance of steel.

Nitrogen (N): The effect of nitrogen on steel properties is similar to that of carbon and phosphorus; it increases strength but decreases plasticity and toughness, worsening weldability and increasing cold brittleness.

Oxygen (O): Oxygen is a harmful element that naturally enters steel during the steelmaking process, mainly existing in the form of inclusions, which reduce the strength and plasticity of steel and severely affect fatigue strength and impact toughness.

Magnesium (Mg): Magnesium can improve the distribution and morphology of inclusions in steel, and trace amounts of magnesium can improve the performance of bearing steel, increasing tensile strength and yield strength.

Aluminum (Al): As a deoxidizer or alloying element, aluminum can refine grains and fix nitrogen, improving impact toughness, and reducing cold brittleness, and aging tendency.

Silicon (Si): Silicon, as a reductant and deoxidizer, can increase the hardness and strength of steel, but more than 3% will reduce plasticity and toughness. Silicon can also increase the elastic limit and fatigue strength of steel.

Phosphorus (P): Phosphorus is a harmful element that can increase strength and hardness but significantly reduce plasticity and toughness, causing cold brittleness.

Sulfur (S): Sulfur, in the form of iron sulfide, causes hot shortness, reducing ductility and toughness, affecting weldability and corrosion resistance.

Potassium/Sodium (K/Na): Potassium/sodium, as a变质剂, can improve the performance of white cast iron and ductile iron.

Calcium (Ca): Calcium can refine grains, improve the corrosion resistance, wear resistance, high-temperature and low-temperature performance of steel, and increase impact toughness and fatigue strength.

Titanium (Ti): Titanium, a strong carbide-forming element, can fix nitrogen and carbon, improve the strength and temper stability of steel, and prevent intergranular corrosion.

Vanadium (V): Vanadium can refine the structure and grains of steel, increase hardenability and temper stability, and produce a secondary hardening effect.

Chromium (Cr): Chromium can increase the hardenability, hardness, and wear resistance of steel and is the main alloying element for stainless and heat-resistant steel.

Manganese (Mn): Manganese can increase the strength and hardenability of steel, improve hot working performance, and eliminate the adverse effects of sulfur.

Cobalt (Co): Cobalt is used in special steels and alloys to improve high-temperature hardness and comprehensive mechanical properties.

Nickel (Ni): Nickel improves the strength, toughness, and hardenability of steel, reduces brittleness temperature, and improves resistance to heat fatigue and corrosion.

Copper (Cu): Copper improves the atmospheric corrosion resistance of ordinary low-alloy steel, increasing strength and yield ratio.

Gallium (Ga): Gallium mainly influences the mechanical properties of steel through solid solution strengthening and has a minor improvement effect on corrosion resistance.

Arsenic (As): Arsenic increases the yield point and tensile strength but increases brittleness and affects weldability.

Selenium (Se): Selenium improves the cutting process performance of carbon steel, stainless steel, and copper.

Zirconium (Zr): Zirconium has deoxidizing, purifying, and grain refining effects, improving low-temperature performance and stamping performance.

Niobium (Nb): Niobium increases the hardenability, temper stability, and hydrogen resistance of steel, refines grains and increases strength.

Molybdenum (Mo): Molybdenum increases the hardenability, heat strength, and corrosion resistance of steel, preventing temper brittleness.

Tin (Sn): Tin plays an important role in electrical steel, cast iron, and free-cutting steel, improving magnetism and cutting performance.

Antimony (Sb): Antimony refines the grains of high magnetic induction-oriented silicon steel and improves magnetism.

Tungsten (W): Tungsten increases temper stability, red hardness, heat strength, and wear resistance.

Lead (Pb): Lead improves cutting process performance but is being gradually replaced due to environmental pollution issues.

Bismuth (Bi): Bismuth improves the cutting performance of free-cutting steel and enhances seismic and tensile properties.

Rare Earth (Re): Rare earth elements can deoxidize, desulfurize, and micro-alloy, improving the deformation ability of inclusions and the fatigue performance of most steel grades.

Conclusion:

In summary, the addition of elements has a profound impact on the performance of steel materials. From improving strength and hardness to enhancing toughness and corrosion resistance, each element contributes in its unique way. However, the application of these elements also requires a delicate balance, as excessive or improper use may bring adverse consequences. Steel manufacturers must optimize the performance of steel according to specific application requirements through scientific formulation and strict production processes.

Different countries' steel production standards and regulations mean that the elemental composition of similar grades, including wear-resistant plates, high-strength steel, and silicon steel, can also vary slightly, leading to subtle differences in actual use. For detailed information on the elemental composition and its impact on performance and practical use of specific grades, especially hot-rolled products, please contact us, and we will provide one-on-one consulting services with steel experts.

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