During the process of steel making, different types of ferro alloy are added as additives in order to improve the quality or enhance the property of the steel.
The benefits of adding ferro alloy
Ferro alloy works as a common additive in steel making process.
In the process of steel making, ferro alloys are added to remove oxygen from molten steel, and some ferro alloys can also remove other impurities in steel such as sulfur and nitrogen.
In the process of steel making, ferro alloys are added as alloying agents to improve the properties of steel.
Types of ferro alloy added
As a deoxidizer for steel making, the most widely used ferro alloys are silicon manganese, ferro manganese, ferro silicon. Strong deoxidizers are aluminum, calcium silicon, silicon zirconium, etc.
As an alloying agent, the widely used ferro alloys are ferromanganese, ferrochrome, ferrosilicon, ferrotungsten, ferromolybdenum, ferrovanadium, ferrotitanium, ferronickel, ferroniobium, rare earth ferro alloy, ferroboron, ferrophosphorus, etc.
Ferrosilicon adding in steel making
Ferrosilicon is an alloy of ferro and silicon. Ferrosilicon is made of coke, steel scrap, quartz as raw materials smelting by electric furnace.
- Ferrosilicon application:
Ferrosilicon is used as a deoxidizer and alloy agent in steel making due to the great affinity between silicon and oxygen.
- Ferrosilicon adding method:
It needs to add a large amount of ferrosilicon for melting silicon steel, spring steel, and heat-resistant steel. The added ferrosilicon must be roasted for a long time because the ferrosilicon contains lots of hydrogen which will be released by roasting.
Meanwhile, the preheated ferrosilicon can melt rapidly. In addition, because the ferrosilicon is light in weight when adding the ferrosilicon in a large amount, a certain part of silicon element is inevitably deoxidized with the furnace slag, creating the acid product of SiO2, which reduces the basicity of furnace slag. It is harmful to the quality of steel.
To prevent it from happening, adding a suitable amount of lime before and after adding the ferrosilicon to keep the basicity of furnace slag, power on high voltage for several minutes, the furnace slag melt and turn to well-proportioned white slag. The recovery rate of ferrosilicon is about 90%-98%.
In the refining melting, adjust the chemical composition and melting temperature before adding ferrosilicon. Tapping of molten steel within 10-25min after adding the ferrosilicon. If the period is too short, the ferrosilicon can’t melt completely, the silicon element hasn’t been well-proportioned in the steel. If the period is too long, the molten steel absorbs the gas and lowers the quality.
Ferrochrome adding in steel making
Ferrochrome is an alloy of ferro and chromium. It is an important alloy additive for steel making
- Ferrochrome application
According to the carbon content, ferrochrome is divided into high carbon ferrochrome, medium carbon ferrochrome, low carbon ferrochrome, micro carbon ferrochrome.
High carbon ferrochrome is used as an alloying agent for high carbon steel balls, tool steel, high-speed steel. It can improve the hardening capacity and abrasive resistance.
Low carbon ferrochrome is used to produce low carbon constructional steel, carburizing steel, gear, etc.
Micro carbon ferrochrome is used to produce stainless steel, acid-resisting steel, heat resistant steel, etc.
- Ferrochrome adding method
Generally, ferrochrome is added at the beginning of the reduction period. The chromium has a greater affinity with oxygen than iron with oxygen., which means that chromium is easier to oxidize than iron.
If added at the melting and oxidizing period, chromium will be oxidized. It is not only loss of the alloying agent, but also make the furnace slag more which affect dephosphorization and smelting process. So ferrochrome should be added in the reduction period.
If the slag turns green after adding the ferrochrome, it means that the slag is deoxidized badly and needs to reinforce the reduction to reduce the FeO in the slag. The slag turns white, which means that the slag is deoxidized well. The recovery rate of ferrochrome is more than 95% at the condition of white slag.
Silico manganese adding in steel making
Silicon manganese is composed of silicon, manganese, iron, and a small amount of carbon and other elements. It is a kind of ferro alloy with large output and widely usage.
- Silicon manganese application
Mn and Si are the main alloying elements in carbon steel. Mn is the leading deoxidizer in steel making. Most of the steel used Mn as a deoxidizer.
- Silicon manganese adding method
Added the silicon manganese at the reduction period. FeO exists in molten steel. Added the silicon manganese, the following chemical reaction occurs:
Si + 2FeO = SiO2 + 2Fe Mn + 2FeO = MnO2 + 2Fe SiO2 and MnO2 reacted and turned into furnace slag.
Ferro manganese adding in steel making
Ferro manganese is composed of iron and manganese. Ferro manganese is used as a deoxidizer and alloying agent in steel making.
- Ferro manganese application
Ferro manganese is used as a deoxidizer, desulfurized, and alloying agent in steel making
Ferro manganese is used to produce low-carbon alloy structural steels and high-quality steels. Without changing the traditional steel-making process, it can optimize alloys, improve the quality of steel, and reduce the cost of steel-making.
- Ferro manganese adding method:
Added ferro manganese at the time of making reducing slag. The recovery rate of ferromanganese is above 95%
Ferrovanadium adding in steel making
Ferrovanadium is composed of iron and vanadium. The content of vanadium is 35-85%.
- Ferrovanadium application
Ferrovanadium is used as an alloying agent in steel making. It is used to produce structural alloy steel, spring steel, tool steel. Added ferrovanadium can improve the strength and toughness of steel.
- Ferrovanadium adding method
Ferrovanadium should be added during the reduction period. It cannot be added during the oxidation period because vanadium is easy to oxidize.
It takes a certain time to melt the ferrovanadium, so it should be added 10-35min before tapping. The recovery rate of ferrovanadium is about 90-98%
With the development of the iron and steel industry, the quality and quantity of ferroalloy have been improved. Almost all deoxidizers, alloy agents, inoculants， and all kinds of alloy cored wire products can be produced in China, which is applied to domestic and foreign steel companies.