HOT METAL PRETREATMENT XỬ LÝ LƯU HUỲNH

2 Sulfur deteriorates tranverse property of steel material..  When the Sulfur content exceeds 0.020%, the Fe-FeS eutectic will precipitate at the grain boundary during solidification..

HOT METAL PRETREATMENT

(De-S)

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7 Comparison between KR and powder injection

8 The effect of desulphurization agent

9 Deslagging

1 Overview

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2 Harmfulness of sulphur

1) Sulfur deteriorates the property of hot working.

2) Sulfur deteriorates tranverse property of steel

material.

3) Sulfur affects the weld-ability of steel materials.

4) Sulfur deteriorates anti-corrosion and conductivity.

Hot crack hiện tượng giòn nóng

 Sulfur exist in steel with the form FeS

　 lưu huỳnh tồn tại trong thép dưới dạng FeS

 Melting point of FeS is 1193 ℃ , and it is 985 ℃ of Fe-FeS eutectic Điểm nóng chảy của FeS là 1193 ℃ , tại 985 ℃ nó là pha cùng tinh Fe-FeS

 In the liquid phase, the FeS can dissolve in Fe indefinitely; but in the solid phase, the dissolubility of FeS reduces to the value of 0.015%~0.020%.

ở pha lỏng, FeS có thể hòa tan vô hạn trong Fe; nhưng ở pha rắn, độ hòa tan của FeS giảm xuống còn 0.015%~0.020%.

 When the Sulfur content exceeds 0.020%, the Fe-FeS eutectic will precipitate at the grain boundary during solidification.

khi hàm lượng lưu huỳnh vượt quá 0.02%, pha cùng tinh Fe-FeS sẽ kết tủa ở biên giới hạt trong suốt quá trình đông đặc

 The hot working temperature of steel is in the range of 1100~1200 o C, the Fe-FeS eutectic will melt at this temperature and cause little cracks in the grain boundaries

ở nhiệt độ cho gia công nóng thép khoảng 1100~1200 o C, pha cùng tinh Fe-FeS sẽ bị nóng chảy ở nhiệt độ này khiến cho biên giới hạt bị đứt gãy

共晶 體熔 點

FeS 熔點

3 Advantage of Pre De-S

4 Hot metal transport

Torpedo Car ( 預 預預 )

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5 Reladling station/pit

4 Methods of De-S ( 預預預預預 )

- There are two methods to De-S in the hot metal:

• Mechanical stirring method ( 預預預預預 ) → FHS using

• Powder injection method ( 預預預 )

- The purpose is to reduce the content of sulphur in hot metal: Charging → Stirring → Reaction → Slag → Skimming

 Equipment 預 Hot Metal Ladle ( 預預

預 )

or Torpedo Car ( 預預預 )

 Add De-S reagent 預 CaC2, CaO, Mg

storage Airtight moisture-proof Airtight moisture-proof

We can using CaC2 or CaO to de-S

But FHT use CaO + CaF 2

CaC2(s)+﹝S﹝=CaS(s)+2﹝C﹝,

Fe 2 SiO

2CaO 2CaS

[Si]

FeS 2

4CaO + + = + ⋅ 2 +

6.1 Mechanical stirring method- KR

CaO + [S] → CaS(s) + [O]

- Treatment time: 38 min

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Running cost

 The table shows the relation

between initial [S] content

and running cost

 With increasing initial [S]

content, flux consumption

increased and therefore

running cost increases

 However, the running cost

is max 1.4 US$/ton

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Impeller

Life time of impeller

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6.2 Powder injection method

- Only use Mg ( 預 ) (Mono-injection):

Mg + [S] → MgS(s)

- Use CaO and Mg (Co-injection):

Mg + CaO + [S] → CaS(s) + MgO(s)

- Life time of lance: 100÷120 heats

- Treatment time: 29 min

Operation cycle time for powder injection method

Lime & Co-injection Carbide/Mg (carbide: 預預預 )

21 SVAI

Main equipments of powder injection

Powder injection station

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7 Comparison between KR

and powder injection

SCPO

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8 The effect of desulfurization agent

- CaO is used widely in

De-S process because it is cheap

and popular

- In powder injection

method, Co-injection is

usually used to desulphurize:

high effect and reduce cost

9 Deslagging ( 預預 )

- Remove sulfur which is trapped in the slag

- It also maintains clean bath surface without any slag and

minimize the iron loss

- Main device: Skimmer

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Slag pot car