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The order in which various ferroalloys are added during the steelmaking process

The order in which various ferroalloys are added during the steelmaking process

The order in which various ferroalloys are added during the steelmaking process

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The order of adding ferroalloys

The order of adding ferroalloys is to add those with weak deoxidizing ability first, then add those with strong deoxidizing ability. Generally, after the slag removal is completed, the carburization operation is completed, part of the slag is added to restore the slag, and then the alloy is added. The joining requirements for different alloys are as follows:

(1) Ferrosilicon

iron silicon alloys
When smelting silicon steel, spring steel and heat-resistant steel, a large amount of ferrosilicon needs to be added for alloying, and the added ferrosilicon must be baked red for a long time. The main reason is that ferrosilicon contains a lot of hydrogen, which can be removed after roasting, and preheating ferrosilicon can also accelerate melting. In addition, because ferrosilicon is light, when a large amount of ferrosilicon is added to the furnace, some silicon will inevitably deoxidize with the slag.

As a result, the acidic product silica is generated, which reduces the alkalinity of the local slag, which is detrimental to the quality of the steel. In order to prevent this situation from happening, an appropriate amount of lime should be added before and after adding ferrosilicon to maintain the alkalinity of the slag, and a high voltage should be used to send electricity for a few minutes to make the slag melt and react well and become a uniform white slag. The recovery rate of ferrosilicon is between 90% and 98%.

In refining, when the chemical composition is adjusted, the temperature is appropriate, and the slag is good, ferrosilicon can be added. After adding, the steel will be tapped within 10-25 minutes. If the time is too short, the ferrosilicon will not have time to completely melt, and the silicon will not be evenly distributed in the steel. If the time is too long, the liquid steel will easily absorb gas and affect the quality of the steel.

(2) Ferromanganese

Medium Carbon Ferromanganese
Ferromanganese can be added while making the slag, and manganese is generally controlled at the lower limit of the composition for the first time. The recovery rate of ferromanganese is above 95%.

(3) Copper

When smelting weathering steel, copper in the steel can improve the hardenability and corrosion resistance of the steel. Copper in the steel is not easily oxidized, so it can be added during charging or during the oxidation period, and the recovery rate is also stable at more than 95%. Since copper is relatively expensive, it is generally best to add a portion of copper-containing pig iron, copper-containing scrap steel or copper-containing iron ore during the melting period, and adjust a small amount of copper during the reduction period to minimize the amount of pure copper used.

(4) Ferrochrome

Ferrochromium is generally added at the beginning of the reduction period. The affinity between chromium and oxygen is greater than the affinity between iron and oxygen, which means that chromium is more easily oxidized than iron. If added during the melting period and oxidation period, chromium will be oxidized, which will not only cause the loss of alloy elements, but also thicken the slag, affecting dephosphorization and smelting operations, so ferrochromium must be added during the reduction period. If the slag turns green after addition, it means that the slag is poorly deoxidized, and the reduction must be strengthened to reduce the chromium oxide in the slag. After good reduction, the slag will turn white. The recovery rate of ferrochromium is greater than 95% under the conditions of white slag during the reduction period.

(5) Ferrovanadium

Ferrovanadium should be added during the reduction period. Vanadium has a high affinity with oxygen and is easily oxidized, so it cannot be added during the oxidation period. It can only be added after the slag and molten steel are well deoxidized during the reduction period. Since the addition of ferrovanadium makes the molten steel easily absorb nitrogen in the air and affects the quality of the steel, it cannot be added too early and can only be added before tapping. However, it takes a certain amount of time to melt ferrovanadium, so it should be added 10-35 minutes before tapping. When the addition amount is small, the time is controlled at the lower limit, and when the addition amount is large, the time is controlled at the mid-to-upper limit. The recovery rate of ferrovanadium is close to that of ferrosilicon.

(6) Ferromolybdenum

Ferromolybdenum is a refractory alloy and is generally added at the beginning of the reduction period to ensure complete melting and uniform composition. If added at a later stage, within a few minutes of tapping, the ferromolybdenum will not have time to completely melt, which may cause uneven distribution in the molten steel and increase the smelting time. The recovery rate of ferromolybdenum is generally greater than 98%.

(7) Ferroniobium

Niobium is an element with a weak affinity for oxygen, so it is easier to control and master during the smelting process. It is generally added at the beginning of the reduction period, and steel can be tapped only after 20 minutes of addition to promote uniform melting. When smelting using the non-oxidation method, niobium can also be added during charging, and the recovery rate of niobium is generally greater than 95%.

(8) Ferrotungsten

Ferrotungsten is characterized by high density and high melting point. After adding, it sinks to the bottom of the furnace and is not easy to melt. Compared with nickel and molybdenum, tungsten has a greater affinity with oxygen. When added during the melting period, tungsten will oxidize and exist in the slag in the form of calcium tungstate, causing the loss of tungsten and making it more difficult to control the composition of tungsten.

Therefore, ferrotungsten should be added in the early stage of the reduction period and cannot be added in the melting period or the late stage of refining. Since ferrotungsten is difficult to melt, adding a large amount in the later stage of refining will affect the smelting time. At the same time, the distribution in the molten steel is also uneven. Most of the ferrotungsten should be added in the reduction period. Added at the beginning of the period, leaving only a small amount to adjust at the end of the reduction period. Moreover, the tungsten iron added must be small and must be roasted red to facilitate melting. The recovery rate of ferrotungsten is generally above 95%.

(9) Aluminum

Aluminum is easily oxidized, so it is usually added just before tapping. For steel types with different aluminum contents, the adding methods are also slightly different: for steel types with an aluminum content lower than 0.2%, generally the slag can be inserted into the furnace 2-5 minutes before tapping. In this way, the aluminum recovery rate is about 50%. If steel contains titanium, the recovery rate is slightly higher, up to 55%.

For steel types with higher aluminum content, in order to prevent the slag from returning to silicon after adding a large amount of aluminum and making the finished silicon exceed the composition requirements, the entire slag removal method is used to remove all the reduced slag, then add aluminum blocks, and then add the aluminum blocks. Finally, add 2%-3% lime and small pieces of fluorspar with low silica content to the molten steel. After the electrolytic slag is evenly distributed, the furnace is shaken to tap out the steel. In this case, the aluminum recovery rate is 65 Between %-88%.

(10) Ferroboron

Boron easily combines with oxygen and nitrogen in steel, and is usually added when steel is tapped. Before adding boron, an appropriate amount of aluminum and titanium must be added to the steel to deoxidize and stabilize nitrogen.

How to add boron:

1) Generally, during the tapping process, ferroboron is added to the ladle. At this time, the tapping operation must first enlarge the tapping hole, and the speed of the furnace is a little faster. At the same time, the slag blocking operation must be performed. The molten steel must first flow into the ladle, and then the molten steel must be allowed to flow into the ladle. When the ladle is about one-third full of molten steel, add ferroboron (put it in or insert it). Then let the slag flow out. Method for blocking slag in front of the furnace: first add a few shovels of lime at the tap hole, block the tap hole with a sawdust rake to remove slag, and then quickly shake the furnace to tap out the steel.

2) After adding aluminum or titanium, insert ferboron in front of the furnace, stir it again, and then tap the steel. At this time, the ferroboron should be firmly tied to the iron rod, and the outside should be wrapped with aluminum skin or horse manure paper. The molten steel should be inserted as quickly as possible to avoid oxidation loss of boron in the slag.
The boron recovery rates of the above two methods are similar, generally 45% to 85%, and may be higher in individual cases. From the perspective of the uniformity of boron in the steel and the inherent quality of the steel, the latter adding method is better.

(11) Ferrotitanium

Titanium has a great affinity with oxygen and nitrogen, and is easily oxidized and nitrided to become inclusions in steel. Therefore, titanium is generally added under white slag conditions and is completely melted before steel is tapped, that is, it is usually finished within 5-15 minutes after addition. Ask for steel. Ferrotitanium should be added near the furnace door to avoid being close to the arc to reduce burning loss. If the quantity is small, there is no need to push the residue after adding. After adding ferrotitanium, staying in the furnace for too long will not only reduce the recovery rate, but also reduce the quality of the molten steel.

In addition, due to the low density of ferrotitanium, it floats on the surface of slag steel when added to the furnace, and then gradually melts into the molten steel. Therefore, the recovery rate fluctuates greatly, and the influencing factors are also more complex.

The main factors affecting titanium recovery rate are:

1) The influence of the amount of slag in the furnace. The burning loss of titanium mainly occurs through slag, so when there is less slag in the furnace, the impact is small and the recovery rate is relatively stable. When the amount of slag is large and the slag is well deoxidized and has suitable fluidity, the burning loss of titanium will be small and stable. If the amount of slag is large and the slag condition is poor, the burning loss of titanium will be large and extremely unstable; if the slag is too thin, the interaction between ferrotitanium and slag will be strengthened, so the recovery rate will decrease.

However, if the slag is too sticky, ferrotitanium will float on the The burning loss on the slag surface is also large, and the recovery rate is also reduced; the slag deoxidation is poor, the iron oxide content in the slag is high, the oxidation loss of titanium is large, and the recovery rate is reduced; the temperature is high, especially the high slag temperature, resulting in burning loss of ferrotitanium. The recovery rate is low. Steel containing high amounts of titanium has a high recovery rate: when steel contains a lot of other deoxidizing elements, the recovery rate is also high. For example, if aluminum and titanium are inserted before adding titanium, the recovery rate can also be improved and stabilized. The ferrotitanium is added to the top of the furnace at one time. Due to the effect of gravity, the ferrotitanium can be directly added to the molten steel, and the recovery rate is also increased.

2) The influence of titanium iron block size. As long as it is not all broken pieces, it is generally not a major factor, but if it is in powder form, the recovery rate of ferrotitanium will be greatly reduced, sometimes less than 25%.

3) The impact of joining methods. Add ferrotitanium after the slag pushing operation, even after using an iron rake to stick the slag, push the reduced slag in the furnace door area until exposed molten steel can be seen, add ferrotitanium immediately. The recovery rate (such as stainless steel) can be stabilized at 60%-65% (the slag condition and temperature have little impact). Generally, structural steel containing silicon and vanadium has a higher degree of deoxidation than stainless steel, so the recovery rate can be as high as about 70%.

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Anyang WeiYuan Alloy Co., Ltd was established in 2011. We specialize in producing various ferroalloys for steel making, including Ferro Silicon, Ferro Chromium, Silicon Carbide, Ferro Manganese, Metal silicon price Calcium Silicon Barium, Metallurgy Nodulant, Silicon Calcium Powder, carbon raiser, etc.

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