STEEL PRODUCTION PROCESS BILLETS AT THE STEEL FACTORY AT PT. KRAKATAU STEEL (PERSERO)Tbk
Steel is an alloy metal, iron as the basic element with carbon as the main alloying element. The function of carbon in steel is as a hardening element by preventing dislocations from shifting in crystals of iron atoms. The properties of steel are strongly influenced by the carbon content. If the carbon content in the steel is greater , the stress and strain will be better .
Electric Arc Furnaces
• Electric Arc Furnance is a type of kitchen where the heat source is obtained from electric electrodes made of carbon. EAF is used to regulate the composition of carbon and alloying elements. In this kitchen, impurity minerals are bound by injection and addition of carbon in the Electric Arc Furnace Process
1. Charging: importing raw materials ( scrap) into the electric furnace to be melted down to become molten iron. Initial charging aims to melt raw materials with an amount of ± 40% of the total load of 38-40 tons of scrap and 2 tons of limestone.
2. Melting: a smelting process in an electric arc furnace so that the raw material in the form of scrap becomes molten metal using three electrodes with a voltage of 3000 Watt which is inserted into the refractory furnace to produce a temperature of 1560 ° C and is melted for ± 60 minutes.
3. Refining: aims to bind/remove unwanted impurities and achieve carbon levels according to the target 4. Tapping: a process of pouring molten steel from an electric furnace into the ladle Ladle Furnace • Ladle furnace is a place for liquid steel (liquid steel) undergoes a purification process and adjusts the composition of the alloying elements to suit the desired steel grade.
• Ladle Furnace Process :
1. De-Oxidation Process
2. De - Sulfurization Process
3. Continuous Casting Machine Alloying Process
• Continuous Casting is the process of casting molten steel into the mold from the ladle to form steel billets continuously Continuous Casting Machine Process The initial stage is that the liquid steel in the ladle is sent to the turret using a crane. After the ladle is in the turret, the ladle is closed with a ladle cover to maintain temperature. The next stage, the slide gate is opened and liquid steel can flow from the ladle to the tundish. After being accommodated in the tundish then distributed to each mold through four nozzles. After that, the Casting process is carried out. Liquid steel that has been printed by the mold will go down to the strand guide. When passing the withdrawal straightening or commonly called the steel strand guide, it will be given spray cooling to make the steel harden. and a length of 12 m using a flame cutting machine and will be sent to the end of the roller table. After that the billet can be moved to the cooling bed area. The cooling process was carried out for ± 30 minutes. Billets that have cooled will then be checked for quality, whether there are defects in the billets. Quality checking can be done visually Flow Process Continuous Casting Machine Damage to Billets
• Damage to the resulting billets. At PT. Krakatau Steel(Persero)Tbk, among others, namely bent (bent), Dent (dent), Scratch (scratches), and corrosion
• From the results of the analysis obtained on these problems, especially on the machine, there are several factors that cause damage to steel billets, including:
1. Worn mold head
2. The crusted mold jacket channel
3. Problematic spray pipelines. Conclusion
• The raw material for making steel billets used is scrap iron, the scrap is obtained from three sources, namely home scrap, imported scrap, and local scrap.
• The machine used and the process for making steel billets consists of several stages, namely the smelting process in the EAF (Electric Arc Furnace), the refining process, the addition of alloying elements in the LF (Ladle Furnace) and the process of casting liquid steel continuously in the CCM (Continuous Casting Machine). ).
• Types of damage to steel billets include bent, dent, scratch, corrosion. The causes of the damage are worn mold heads, problematic spray pipelines, crusty mold jacket ducts, improper material buildup, and because air containing acid creates moist magnesium oxide. Methods of handling include repairing problematic spray pipe lines, lubricating worn mold heads, and repairing damaged dies.
