Definition of Aluminum Killed Steel: It is the type of steel in which oxygen is removed with the help of aluminum so as to minimize or eradicate the presence of oxygen to a least level so that no chemical process results with oxygen and carbon during steel solidification process. These steels are specially processed steels. These are high performance & specially manufactured for special applications at high temperatures and are specialized industrial grades.
US Patent No. US 3357822: It specifies an invention titled as “Low-carbon aluminum killed steel for high temperature applications“. This invention refers to material grade of steels designed for elevated temperature applications which has robust ability to weld and reflects greater strength in high degree of temperature devoid of toughness losses.
Types of Killed Steels: There are mainly two types of Killed steels i.e. Killed steel and Semi Killed Steel.
Aluminum Killed steel is type of steel that has been entirely deoxidized by the addition of aluminum (or any other additive in case of other killed steels other than aluminum) prior to casting, so that there is in reality no introduction of gas throughout solidification. This type is graded by an elevated level of chemical similarity and almost no presence of gas porosity. The steel is referred to be “killed” for the reason that it will silently go through solidification process in the mould, with no gas getting out of the mould. It is usually labelled in industries with a “K” for representation & marking objectives.
Aluminum Semi-killed steel is partly or semi deoxidized grade of steel with the help of aluminum, since the carbon monoxide is allowed to leave bubble out kind of porosity shared homogeneously all through the ingot. The porosity eradicated the pipe present in fully aluminum killed steel and augments the yield strength by weight to around ninety percent. Aluminum Semi-killed steel is generally utilized for structural steel with a carbon content contained in the range of percent fifteen hundredth to percent twenty five hundredth, since it is then rolled, which embeds the porosity and removes it. It is also utilized for various drawing usages.
Addition of Aluminum: Normally aluminum is brought to molten steel so as to gain comprehensive deoxidation and fine & sharp grain structures. It is beautifully understood, on the other hand, the fact that inclusion of a big quantity of aluminum drives to decrease the strength of material at high-temperature specially for the low carbon steel. Because of this phenomenon, the aluminum is then mixed with the nitrogen to produce AlN, together with a relevant deduction in the quantity of nitrogen in the shape of solid solution, which has a vital impact on the strength at high-temperature of the material.
Examples of Aluminum Killed Steels: Following are the examples for Aluminum killed steels:
- ISO 3575 defines 04 grade steel as special killed cold rolled steel.
- A 653/A 653M-05 defines EDDS Steel as killed steel which is a Galvanized Extra Deep Drawing Cold Rolled Steel.
- JIS G3302 also defines SGCD4 killed steel as Galvanized Extra Deep Drawing Cold Rolled Steel.