The materials of coiled tubing are among the most commonly used alloys and essentially a combination of carbon and iron. It also contains other elements, some of which are retained from the steel making process, other constituents are added to produce specific properties.
The most common elements are listed below:

Aluminum (Al)
When added to molten steel, mixes very quickly with any undissolved oxygen and is therefore considered one of the most common deoxidizers in making steel. Aluminum is also used to produce a fine grain structure and to control grain growth.

Carbon (C)
The basic metal, iron, is alloyed with carbon to make steel which has the effect of increasing the hardness and strength of iron. Pure iron cannot be hardened or strengthened by heat treatment but the addition of carbon enables a wide range of hardness and strength.

Chromium (Cr)
Chromium is added to the steel to increase its resistance towards oxidation. This resistance increases as more chromium is added. 'Stainless Steel' has approximately 11% chromium and a remarkable degree of general corrosion resistance when compared to steels with a lower percentage of chromium. When added to low alloy steels, chromium can increase the response to heat treatment, thus improving hardenability and strength.

Cobalt (Co)
Is used to increase the red hardness of a steel. It adds much life to a tool by its ability to maintain hardness and cutting ability when it's heated to a dull red during a machining operation.

Copper (Cu)
Copper is usally present in Stainless Steels as a residual element. However it is added to a few alloys to produce precipitation hardening properties.

Iron (Fe)
Although it lacks strength, is very soft, ductile and does not respond to heat treatment to any degree, iron is the primary element in steel. With the addition of other alloying elements required mechanical properties can be achieved.

Manganese (Mn)
Its presence has three main effects. It is a mild de-oxidant acting as a cleanser taking the sulphur and oxygen out of the melt into the slag. Manganese increases hardenability and tensile strength but decreases ductility and combines with sulphur to form manganese sulphides, essential in free cutting steels.

Molybdenum (Mo)
Molybdenum, when added to chromium-nickel austenitic steels, improves resistance to pitting corrosion especially by chlorides and sulphur chemicals. When added to low alloy steels, molybdenum improves high temperature strength and hardness. When added to chromium steels it greatly diminishes the tendency of the steel to decay in service or heat treatment.

Nickel (Ni)
When added to carbon steel in amounts up to 5% it increases the tensile strength, toughness and hardenability without loss of ductility. Often used in combination with other alloying elements, especially chromium and molybdenum, Stainless steels contain between 8% and 14% nickel.

Niobium (Nb/Cb)
Niobium (Columbium) increases the yield strength and, to a lesser degree, the tensile strength of carbon steel. The addition of small amounts of Niobium can significantly increase the yield strength of steels. Niobium can also have a moderate precipitation strengthening effect. Its main contributions are to form precipitates above the transformation temperature and to retard the recrystallization of austenite, thus promoting a fine-grain microstructure with improved strength and toughness.

Nitrogen (N)
Nitrogen has the effect of increasing the austenitic stability of Stainless Steels and is, as in the case of nickel, an austenitic forming element. Yield strength is greatly improved when nitrogen is added to austenitic stainless steels.

Phosphorus (P)
Although it increases the tensile strength of steel and improves machinability it is usually regarded as an undesirable impurity because of its embrittling effect. Most steels do not exceed 0.05% phosphorus.

Silicon (Si)
In most commercial steels it is present in a range of 0.05-0.35% and acts as a powerful deoxidizing agent. It is present in higher contents in Silicon-Manganese Spring Steels as well as acid and heat resisting steels.

Sulphur (S)
When added in small amounts sulphur improves machinability but does not cause hot shortness. Hot shortness is reduced by the addition of manganese, which combines with the sulphur to form manganese sulphide. As manganese sulphide has a higher melting point than iron sulphide, which would form if manganese was not present, the weak spots at the grain boundaries are greatly reduced during hot working.

Tantalum (Ta)
Chemically similar to niobium and has similar effects.

Titanium (Ti)
The main use of titanium as an alloying element in steel is for carbide stabilisation. It combines with carbon to form titanium carbides which are quite stable and hard to dissolve in steel. This tends to minimise the occurrence of inter-granular corrosion, as with A.I.S.I 321. When adding approximately 0.25%-0.60% titanium, the carbon combines with the titanium rather than chromium, preventing a tie-up of corrosion resisting chromium as inter-granular carbides and the accompanying loss of corrosion resistance at the grain boundaries.

Vanadium (V)
Vanadium is a strong deoxidizer and promotes fine grain structure. It counteracts softening at elevated temperatures and steels with Vanadium seem to resist shocks better than steels without it.