CN1327073A

CN1327073A - Compound iron melt desulfurizing agent

Info

Publication number: CN1327073A
Application number: CN 01114232
Authority: CN
Inventors: 刘星; 程益红
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-05-31
Filing date: 2001-05-31
Publication date: 2001-12-19
Anticipated expiration: 2021-05-31
Also published as: CN1154748C

Abstract

The compound iron melt desulfurizing agent consists of CaC2 36-48 wt%, CaO 32-44 wt%, CaF2 3-7 wt%, C 3-7 wt% and Mg 0-7 wt% other than impurities including SiO2, MgO, Al2O3 and CO2. The desulfurizing agent can result in a desulfurizing rate of 75-90 % to make iron melt with sulfur content of 0.003%. That is, the desulfurizing agent can meet the requirement of deep desulfurizing without significant increase of cost.

Description

Composite molten iron desulfurizing agent

The invention relates to a molten iron desulfurizer in a metallurgical steelmaking process, in particular to a composite molten iron desulfurizer which can meet the requirement of deep desulfurization of molten iron in steelmaking.

With the popularization of the strengthening smelting process and the increase of the requirements of steel varieties, the requirements of steel on sulfur control are higher and higher, and not only is a perfect secondary refining and secondary desulfurization process required to obtain low-sulfur molten steel, but also a low-sulfur main raw material and a low-sulfur auxiliary raw material are required, and the sulfur content of molten iron serving asthe main raw material is required to be 0.002% -0.004%, so that the molten steel components of a final finished product can be ensured.

The traditional molten iron desulfurizing agent has three types, and the components are single and have respective advantages and disadvantages. One is to use calcium carbide powder (CaC2) for desulfurization, which has strong desulfurization capability, but the calcium carbide powder is easy to absorb moisture and release explosive gas C2H2, the desulfurization capability of the calcium carbide can be greatly reduced after moisture absorption, and the cost is higher; the other one is desulfurization by using lime powder (CaO), which has low price, easy processing and safe use, but has limited CaO desulfurization capability, large using amount and poor fluidity; the other desulfurizing agent is Mg powder which has very strong desulfurizing capacity and is greatly higher than that of CaO, but Mg is gasified after entering molten iron and reacts very strongly, so that pure Mg is not used generally but is mixed with other materials for use, and the price of Mg is high. There are also desulfurizers which mix the above three substances together in a certain proportion, but they are expensive and the desulfurizing effect is not very obvious.

The invention aims to provide a composite molten iron desulfurizer which can deeply desulfurize and reduce the sulfur content of molten iron to a desired value without excessively increasing the cost. .

In order to achieve the purpose, the composite molten iron desulfurizer of the invention comprises the following components in percentage by weight: CaC 236-48 CaO 32-44 CaF 23-7C 3-7 Mg 0-7, and the balance of impurities, wherein the sum of the weight of the above components is 100%.

The desulfurizer comprises the following components in percentage by weight: CaC 238-46 CaO 33-40 CaF 24-7C 3-5 Mg 3-6, and the balance of impurities, wherein the sum of the weight of the components is 100%.

The effects of the present invention will be described below by specifically analyzing the effects and characteristics of the components of the present invention and referring to examples.

1. The CaC2 desulfurization method has the following characteristics:

1) the calcium carbide desulfurization reaction comprises the following steps:

ΔG＝-359245＋109.5t.j/mol

in the high-carbon molten iron, Ca ions decomposed by CaC2 have strong strength with sulfur in the molten iron

Thus CaC2 has a strong desulfurization ability.

2) The CaC2 is used for desulfurization, and the desulfurization reaction is an exothermic reaction, which is beneficial to reducing the temperature drop of molten iron.

3) The melting point of the desulfurization product CaS is 2450 ℃, so that the desulfurization product is formed on the surface of molten iron

Loose solid slag is beneficial to preventing resulfurization, and the corrosion to the inner lining of the mixer car is light,

the slag skimming operation is convenient.

4) The calcium carbide powder CaC2 has strong desulfurization capability, small using amount and small slag amount.

5) Calcium carbide powder CaC2 is easy to absorb moisture, and the following reaction is generated during moisture absorption:

this reaction greatly reduces the desulfurization ability of the calcium carbide powder, and the evolved C2H2 is an explosive gas, and therefore nitrogen is used for sealing during transport and storage of the calcium carbide powder.

As the cost of the calcium carbide powder is more expensive than that of lime, the 36-48 percent of CaC2 is matched in the invention, so that the cost can be relatively reduced and the aim of deep desulfurization can be fulfilled compared with the desulfurization by pure CaC 2.

2. The CaO desulfurization in the invention has the following characteristics:

1) the desulfurization ability of CaO is relatively much weaker than that of CaC 2.

2) The desulfurized slag is solid slag, the slag skimming is convenient, the corrosion to the hot metal ladle and the hot metal mixer is small,

but the dosage is larger, so the amount of formed slag is also large, the iron loss is also higher, and the temperature drop of the molten iron is also higher

Is relatively large.

3) The lime powder has wide resource, low price, easy processing and safe use.

4) The lime powder has poor fluidity and is easy to block in transportation, and the lime powder can be put in a material tank

Bridging and blocking materials, and the lime powder is easy to absorb moisture.

In view of the above characteristics of CaO desulfurization, 32-44% of CaO is added in the invention, so that the advantages of the CaO desulfurization agent can be fully utilized, and the defects of the CaO desulfurization agent can be reduced.

3. CaF2 has no desulfurization capability, but the addition of CaF2 powder in the present invention results in a significant increase in the desulfurization rate of CaO and a reduction in the sulfur content, which has been confirmed in practice, so that a certain amount of CaF2 is generally formulated for desulfurization with CaO.

4. The function of C in the invention: for desulfurization with CaO, the following reaction occurs:

thus, the addition of carbon favours the desulfurization, in tests we have found that a desulfurizing agent with 3% to 7% C is very favourable for desulfurization, and that carbon favours the flow of the mix in the duct.

5. The magnesium powder desulfurization of the invention has the following characteristics:

1) mg has strong molten iron desulphurization capability, is higher than that of CaC2 and is greatly higher than that of CaC2

The desulfurization ability of CaO.

2) The boiling point of Mg is 1107 ℃, and Mg is changed into Mg vapor to form gas after being added into molten iron

Bubbling to make Mg desulfurization reaction proceed on gas-liquid phase interface, Mg steam stirring is large

Greatly enhancing the desulfurization effect of Mg.

3) Mg has certain solubility in molten iron, and the molten iron can be prevented from being saturated by Mg

Resulfurization, the saturated Mg can be removed in the transportation process after molten iron treatment

And (4) sulfur action.

4) Since Mg is gasified after entering molten iron and the reaction is very strong, it is common

Not using pure Mg, but mixing with other materials and spraying, at present, the Mg-CaO powder is often mixed with CaO powder

And mixing to obtain the mixed desulfurizer.

5) Mg is expensive, but Mg mixtures can be used if they are mixed in a suitable ratio

The quantity is reduced, and the method has the characteristics of less temperature drop of the molten iron, less slag quantity, less iron loss and the like.

The invention is provided with about 4 percent of Mg, which is proved to be an ideal proportion in the test, does not increase the comprehensive cost greatly, but can achieve the aim of deep desulfurization.

6. The impurities in the invention comprise SiO2, MgO, Al2O3, CO2 and the like, which do not have great influence on desulfurization, but are inevitably brought into the actual production process of the desulfurizer.

The above components are obtained by optimization and comparison in the test process, the sulfur in the molten iron can be averagely removed to 0.003 percent, the desulfurization rate reaches 75 to 90 percent, and the requirement of deep desulfurization of the molten iron can be fully met. The desulfurizer can achieve the purpose of deep desulfurization on the basis of less increase of the cost of per ton of steel, and has very wide practical application value.

Example 1:

100 kg of the desulfurizer comprises the following components: CaC 242 kg CaO 38kg CaF 25 kg C5 kg Mg 4kg impurity 6kg

The mixture is crushed to 0.1 to-0.8 mm, 5.5 kilograms of the desulfurizer is sprayed into per ton of iron by a powder spraying method, the sulfur content of the molten iron can be reduced from 0.025 percent to 0.0035 percent on the premise of ensuring full stirring, and the desulfurization rate reaches 86 percent.

Example 2:

100 kg of the desulfurizer comprises the following components: CaC 244 kg CaO 35kg CaF 24 kg C4 kg Mg 6kg impurity 7kg

The mixture is crushed to 0.1 to 0.8mm, 5.5 kg of 0.1 to 0.8mm of the desulfurizer is sprayed into per ton of iron by a powder spraying method, the sulfur content of the molten iron can be reduced from 0.025 to 0.0028 percent on the premise of ensuring full stirring, and the desulfurization rate reaches 88.8 percent.

Example 3:

100 kg of the desulfurizer comprises the following components: CaC 248 kg CaO 32kg CaF 23 kg C3 kg Mg 7kg impurity 7kg

The mixture is crushed to 0.1 to-0.8 mm, 6.5 kg of 0.1 to 0.8mm of the desulfurizer is sprayed into per ton of iron by a powder spraying method, the sulfur content of the molten iron can be reduced from 0.02 percent to 0.0018 percent on the premise of ensuring full stirring, and the desulfurization rate reaches 91 percent.

Example 4:

100 kg of the desulfurizer comprises the following components: CaC 246 kg CaO 32kg CaF 27 kg C3 kg Mg 3kg impurity 9kg

The mixture is crushed to 0.1 to-0.8 mm, 6.5 kg of 0.1 to 0.8mm of the desulfurizing agent is sprayed into one ton of molten iron by a powder spraying method, the sulfur content of the molten iron can be reduced from 0.022 percent to 0.0026 percent on the premise of ensuring full stirring, and the desulfurization rate reaches 88.2 percent.

Example 5:

100 kg of the desulfurizer comprises the following components: CaC 248 kg CaO 36kg CaF 23 kg C7 kg Mg 0kg impurity 6kg

The mixture is crushed to 0.1 to-0.8 mm, 6kg of the desulfurizing agent with the diameter of 0.1 to 0.8mm is sprayed into one ton of molten iron by a powder spraying method, the sulfur content of the molten iron can be reduced from 0.026% to 0.0038% under the condition of full stirring, and the desulfurization rate reaches 85.4%.

Example 6:

100 kg of the desulfurizer comprises the following components: CaC 240 kg CaO 40kg CaF 25 kg C4 kg Mg 4kg impurity 7kg

The mixture is crushed to 0.1 to-0.8 mm, 6kg of the desulfurizing agent with the diameter of 0.1 to 0.8mm is sprayed into one ton of molten iron by a powder spraying method, the sulfur content of the molten iron can be reduced from 0.024 percent to 0.004 percent under the condition of full stirring, and the desulfurization rate reaches 83.3 percent.

Example 7:

100 kg of the desulfurizer comprises the following components: CaC 238 kg CaO 44kg CaF 23 kg C5 kg Mg 6kg impurity 4kg

The mixture is crushed to 0.1-0.8 mm, 6.5 kg of 0.1-0.8 mm desulfurizing agent is sprayed into per ton of molten iron by a powder spraying method, the sulfur content of the molten iron can be reduced from 0.02% to 0.0035% under the condition of full stirring, and the desulfurization rate reaches 82.5%.

Example 8:

100 kg of the desulfurizer comprises the following components: CaC 236 kg CaO 44kg CaF 24 kg C7 kg Mg 3kg impurity 6kg

The mixture is crushed to 0.1 to-0.8 mm, 6.5 kg of 0.1 to 0.8mm desulfurizing agent is sprayed into per ton of molten iron by a powder spraying method, the sulfur content of the molten iron can be reduced from 0.02 percent to 0.0042 percent under the condition of full stirring, and the desulfurization rate reaches 79 percent.

In conclusion, the invention is novel and practical, the optimal proportion of the desulfurizer not only can ensure that the desulfurizer has stronger desulfurization capability, but also has lower cost, and compared with the background technology, the desulfurizer has outstanding substantive characteristics and remarkable progress, and has patentability.

Claims

1. The composite molten iron desulfurizer is characterized by comprising the following components in percentage by weight: CaC 236-48 CaO 32-44 CaF 23-7C 3-7 Mg 0-7, and the balance of impurities, wherein the sum of the weight of the above components is 100%.

2. The compound molten iron desulfurizer as claimed in claim 1, wherein the optimum weight percentage of components of the desulfurizer is as follows: CaC 238-46 CaO 35-40 CaF 24-7C 3-5 Mg 3-6, and the balance of impurities, wherein the sum of the weight of the components is 100%.