Effect of alloying elements

[arcpro]

Carbon
1. Amount of carbon in steel limits its type to be made.
2. As C content increases in Rimmed steels, its surface quality deteriorates.
3. In Killed steels, C content in the range of 0.15 - 0.3 % may have poor surface quality and require surface processing to attain required quality compared to steel with higher or even lower C content.
4. Carbon plays an important role in macrosegregation during solidification and it is more significant then any other alloying element.
5. Carbide forming elements interact with carbon and form alloy carbides.
6. Carbon is the main hardening element in all steels except austenitic PH Stainless Steels.
7. And finally, as C content increases in steel, it induces strength but ductility and weldability decrease.

Keep adding guys.

[qaisarabbas]

For CARBON:
8. ASME B&PV code prohibits welding or thermal cutting of carbon or alloy steel with a carbon content of over 0.35%. Higher carbon can cause zones of high hardness and impart adverse properties at weld and HAZ. (PW-5.2)

[arcpro]

Silicon
1. Silicon (Si) is one of the principal deoxidizers used in steel making.
2. Silicon content also determines the type of steel produced.
3. Killed carbon steels may contain Si up to a maximum of 0.60%.
4. Semikilled steels may contain moderate amounts of Si.
5. For example, in rimmed steel, the Si content is generally less than 0.10%. Silicon dissolves completely in ferrite, when silicon content is below 0.30%, increasing its strength without greatly decreasing ductility.
6. Beyond 0.40% Si, a marked decrease in ductility is noticed in plain carbon steels.
7. If combined with Mn or Mo, silicon may produce greater hardenability of steels.
8. Due to the addition of Si, stress corrosion can be eliminated in Cr–Ni austenitic steels. In heat treated steels, Si is an important alloy element, and increases hardenability, wear resistance, elastic limit and yield strength, and scale resistance in heat-resistant steels.
9. Si is a non-carbide former, and free from cementite or carbides; it dissolves in martensite and retards the decomposition of alloying martensite up to 300 C.

[arcpro]

Manganese
1. Manganese (Mn) is present in virtually all steels in amounts of 0.30% or more.
2. Manganese is essentially a deoxidizer and a desulfurizer.
3. It has a lesser tendency for macrosegregation than any of the common elements.
4. Steels above 0.60% Mn cannot be readily rimmed. Manganese is beneficial to surface quality in all carbon ranges (with the exception of extremely low-carbon rimmed steels) and reduction in the risk of red-shortness.
5. Manganese favorably affects forgeability and weldability.
6. Manganese is a weak carbide former, only dissolving in cementite, and forms alloying cementite in steels.
7. Manganese is an austenite former as a result of the open gamma-phase field.
8. Large quantities (>2% Mn) result in an increased tendency toward cracking and distortion during quenching.
9. The presence of alloying element Mn in steels enhances the impurities such as P, Sn, Sb, and As segregating to grain boundaries and induces temper embrittlement.

[inconel]

Dear,

Could you please mention the ASME BPV section and clause for reference?

Regards,

Inconel

For CARBON:
8. ASME B&PV code prohibits welding or thermal cutting of carbon or alloy steel with a carbon content of over 0.35%. Higher carbon can cause zones of high hardness and impart adverse properties at weld and HAZ. (PW-5.2)

[ben]

This clause mentioned by qaisarabbas is in ASME Sec. I for power boilers (PW-5.2) under Materials (PW-5) and not in ASME Sec. VIII for pressure vessels.

[arcpro]

Phosphorus
1. Phosphorus (P) segregates during solidification, but to a lesser extent than C and S.
2. Phosphorus dissolves in ferrite and increases the strength of steels. As the amount of P increases, the ductility and impact toughness of steels decrease, and raises the cold-shortness.
3. Phosphorus has a very strong tendency to segregate at the grain boundaries, and causes the temper embrittlement of alloying steels, especially in Mn, Cr, Mn–Si, Cr–Ni, and Cr–Mn steels.
4. Phosphorus also increases the hardenability and retards the decomposition of martensite-like Si in steels.
5. High P content is often specified in low-carbon free-machining steels to improve machinability.
6. In low-alloy structural steels containing ~0.1% C, P increases strength and atmospheric corrosion resistance.
7. In austenitic Cr–Ni steels, the addition of P can cause precipitation effects and an increase in yield points.
8. In strong oxidizing agent, P causes grain boundary corrosion in austenitic stainless steels after solid solution treatment as a result of the segregation of P at grain boundaries.

[arcpro]

Aluminium
1. Aluminum (Al) is widely used as a deoxidizer and a grain refiner.
2. As Al forms very hard nitrides with nitrogen, it is usually an alloying element in nitriding steels.
3. It increases scaling resistance and is therefore often added to heat-resistant steels and alloys.
4. In precipitation hardening stainless steels, Al can be used as an alloying element, causing precipitation hardening reaction.
5. Aluminum increases the corrosion resistance in low-carbon corrosion-resisting steels.
6. Of all the alloying elements, Al is one of the most effective elements in controlling grain growth prior to quenching.
7. Aluminum has the drawback of a tendency to promote graphitization.

[arcpro]

Nitrogen
1. It can expand and stabilize the austenitic structure, and partly substitute Ni in austenitic steels.
2. If the nitride forming elements V, Nb, and Ti are added to high-strength low-alloy (HSLA) steels, fine nitrides and carbonitrides will form during controlled rolling and controlled cooling.
3. Nitrogen can be used as an alloying element in microalloying steels or austenitic stainless steels, causing precipitation or solid solution strengthening.
4. Nitrogen induces strain aging, quench aging, and blue brittleness in low-carbon steels.