WO2009146573A1

WO2009146573A1 - A composite ball used to precisely control the quantity of the trace element dissolved in the molten steel and the method of producing the composite ball

Info

Publication number: WO2009146573A1
Application number: PCT/CN2008/001073
Authority: WO
Inventors: 唐复平; 王晓峰; 刘万山; 孟劲松; 任子平; 李德刚; 陈本文; 王仁贵; 张军; 王文仲; 李镇; 张晓军; 孙群; 栗红; 常桂华
Original assignee: 鞍钢股份有限公司
Priority date: 2008-06-02
Filing date: 2008-06-02
Publication date: 2009-12-10

Abstract

A composite ball used in secondary refining process and the method of producing the composite ball are illustrated. The composite ball can be used to precisely control quantity of the trace element dissolved in molten steel. The composite ball is consisted of core and shell. The core material contains trace element and expansion agent. The shell material is consisted of CaO, MgO or the mixture of the two. The composite ball can notably improve steady and effective recovery of the trace element in the molten steel and its recovery rate is about 70-95%.

Description

Composite sphere for controlling precise addition of trace elements in steel and preparation method thereof

The invention relates to an off-furnace refining technology for steel making, in particular to a composite sphere for controlling the precise addition of trace elements in steel and a preparation method thereof, and belongs to the technical field of metallurgy.

Background technique

Some trace elements in steel have a significant effect on improving the mechanical properties of the material. For example, boron or rare earth. In some engineering machinery steels, in order to improve the hardenability, a small amount of boron is often added to the steel, and the rare earth can refine the grains, purify the grain boundaries, and change the properties of non-metallic inclusions in the steel. , size, quantity and distribution, which significantly improve the toughness and corrosion resistance of steel.

For the production of boron steel, since the chemical properties of boron are very active, it is easy to react with elements such as oxygen and nitrogen in the steel during the alloying process, resulting in a low yield of boron and an unstable yield. In addition, since the rare earth element itself has strong chemical activity, the rare earth content in the more accurate control material is also a key technology in the popularization and application of rare earth-containing steel and metal materials, because the addition amount of rare earth element and boron is difficult to control. The steel companies and their users cannot formulate steel or other materials according to the normal standard of boron or rare earth elements in the steel or materials, only the amount of boron or rare earth elements in the steel or materials, international academic circles In the discussion of boron steel or rare earth steel, various properties are closely related to the content of boron or rare earth elements. Under such circumstances, it is urgent to solve the technical problem of accurately adding trace elements such as boron and rare earth in the controlled steel.

Summary of the invention

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems in the prior art, and its object is to provide a composite sphere which is suitable for precise and stable control of the addition of trace alloying elements in steel during refining.

Another object of the present invention is to provide a process for producing the above composite sphere. The accurate yield of the addition of trace alloying elements in steel by the method of the present invention is 70% to 95%.

The weight ranges of the components of the present invention are summarized by a large number of explorations and tests by the inventors, and each of the raw materials has a good effect in the following weight range.

1 Confirmation In order to solve the above technical problems, the present invention is achieved by: a composite sphere for controlling the precise addition of trace elements in steel, wherein the core of the composite sphere comprises: a trace element and a swelling agent, and the outer shell of the composite sphere is oxidized Calcium, magnesium oxide or a mixture of calcium oxide and magnesium oxide.

The core of the composite sphere is made up of the following raw materials by weight: 0.1%~99 of trace elements; 1%~70% of expansion agent; 0~30% _of binder.

The preferred weight percentage of each raw material of the core of the composite sphere is: trace element 30%~80%; expander 8%~55%; binder 5%~15%.

The outer shell of the composite sphere further comprises 0 to 20% of a binder.

The trace elements include: Fe-18% B intermediate alloy, Fe-30% RE intermediate alloy.

In the Fe-30%RE master alloy, RE is a mixed rare earth rich in Ce, La, a mixed rare earth rich in Ce or Nd, or a pure rare earth Ce, Nd, La, Gd, Sm.

The expansion agent is composed of a mixture of calcium carbonate, magnesium carbonate or calcium carbonate and magnesium carbonate.

The binder is any one or more of clay, ordinary cement, bentonite, and water glass.

The carbonate as a swelling agent in the above composite sphere effectively promotes diffusion and homogenization of trace elements in the molten steel; calcium oxide and magnesium oxide as stabilizers can improve the thermal stability of the composite sphere; The active ingredient, through the binder of clay, ordinary cement, bentonite and water glass, achieves the control of the binding strength of each active ingredient in the composite sphere.

A method of preparing a composite sphere for controlling the precise addition of trace elements in steel comprises the following steps:

1), preparing a core of the composite sphere:

(a), compounding: crushing and crushing the solid raw materials required by the core according to the ratio, so that the particle size is Inn! ~ 3.5mm, then put the above powder and binder into the mixer for thorough mixing and mixing, the mixing time is 1 h~3h.

(b), drying: drying the above-mentioned mixed raw materials in a dryer, drying temperature It is 80 ° C ~ 150 ° C, the time is 2 h ~ 8 h.

(c), ball making: The raw material after the drying process is made into a ball by a ball making device, and the diameter of the ball is lmm~40mmo

2), preparing the composite sphere:

(d), shell: According to the ratio, the powder required for the outer shell is thoroughly mixed in the mixer. The activity of calcium oxide and magnesium oxide is 200ml, and the mixing time is l h~3h.

(e) Sphere compounding: The prepared core ball and the shell material are compositely ball-formed on a ball making machine by a rolling method, the thickness of the outer shell is 0.1 mm to 20 mm, and the prepared composite sphere size is between 1.2 mm and 80 mm. Just fine.

(f), overall drying: The composite sphere prepared in the above step is dried in a dryer, and the drying temperature is 60 ° C to 200 ° C, and the time is 10 h to 24 h.

The advantages and benefits of the present invention are as follows:

(1) The composite sphere of the present invention has a high thermal stability, a 160 CTC time-delay, a reaction time of 5 s to 35 s, a high compactness, and a compressive strength of 5 MPa to 30 MPa, so that the present invention can sufficiently invade the inside of the molten steel. Therefore, the stable and effective recovery of trace elements in steel can be significantly improved, and the yield can reach 70% to 95%. Therefore, it is more accurate to ensure the total amount of trace elements and solid solution in the steel, thereby effectively improving the performance of the steel and meeting the user's requirements.

(2) Since the effective yield of the trace elements is improved by the present invention, the consumption of trace elements in the steel can be reduced, and the cost is saved.

(3) The composite sphere of the present invention has high compressive strength so as not to be broken during transportation, storage and use.

(4) The process of the invention is simple, flexible, convenient and easy to operate.

detailed description

The beneficial effects of the composite sphere of the present invention are further illustrated by experiments below.

The following steelmaking refining process, with or without the addition of the composite sphere of the invention to the trace elements in the steel The yield is compared: After the ladle is transported to the RH refining process, after 7 minutes of net circulation, when the vacuum is lower than 80 Pa, the composite sphere containing trace elements is added from the lower inlet of the RH down tube; after the composite sphere is added Cycle lmin, continuous casting is available.

Referring to the above table, before adding the composite sphere of the present invention, the content of trace elements in the steel is sampled and analyzed.

0.0001%~0.0003%, after adding the composite sphere of the invention, the yield of the trace element in the finished steel is 70%~95%.

The invention is further described in detail below with reference to the specific embodiments, but the scope of the invention is not limited by the specific embodiments. In addition, any changes or modifications that are easily made by those skilled in the art without departing from the scope of the present invention will fall within the scope of the appended claims.

a composite sphere for controlling the precise addition of trace elements in steel, wherein the core of the composite sphere comprises: a trace element and a swelling agent, and the outer shell of the composite sphere is composed of a mixture of calcium oxide or magnesium oxide or calcium oxide and magnesium oxide. .

Example 1

The composite sphere of the invention is prepared according to the weight percentage of the following raw materials - According to the formula, the core is made of Fe-18%B intermediate alloy 0.1%, calcium carbonate 70%, clay 29.9%; the outer shell is prepared by mixing 1% ordinary cement with calcium oxide.

The preparation method of the composite sphere of the invention comprises the following steps:

1), preparing a core of the composite sphere:

(a) Mixing: The solid raw material required for the above core is crushed and crushed according to the above ratio, and is also ground by micro-grinding to obtain a particle size of 10 nm to 2.5 mm, and then the powder is mixed. The mixture is thoroughly stirred and mixed, and the mixing time is lh~2h. (b) Drying: The above mixed raw materials are dried in a dryer at a drying temperature of 80 ° C to 120 ° C for a period of 2 h to 4 h. (c), ball making: The above-mentioned dried raw materials are ball-formed on a disc granulator by a rolling method, and the rotation speed of the disc granulator is 400 to 1600 r/min, and the control of the sphere size is determined by sieving to obtain The diameter of the sphere is from 1 mm to 10 mm.

2), preparing the composite sphere:

(d), shell: The powder required to take the outer shell according to the above ratio is thoroughly mixed in the mixer, the activity of calcium oxide is 200ml, and the mixing time is lh~2h. (e) Sphere compounding: The prepared core ball and the shell material are compositely ball-formed on a disc granulator by a rolling method, and the thickness of the outer shell is 0.1 mm to 2 mm, and the size of the sphere is controlled by sieving. The finished composite sphere size is 1.2mn! ~ 14mm can be. (f), overall drying: The composite sphere prepared in the above step is dried in a dryer, and the drying temperature is 80 ° C to 120 ° C, and the time is 10 h to 20 h.

Example 2

The composite sphere of the present invention is prepared in the weight percentage of the following raw materials:

According to the formula, the core is made of Fe-18%B master alloy 55%, calcium carbonate 44%, bentonite 1%; the shell is prepared by mixing 10% clay with a mixture of calcium oxide and magnesium oxide.

1), preparing a core of the composite sphere:

(a), compounding: crushing and crushing the solid raw materials required for the above core according to the above ratio, At the same time, the airflow is micromilled and ground to a particle size of 10 nm to 20 mm, and the powder is placed in a mixer for thorough mixing and mixing, and the mixing time is 1.5 to 3 hours. (b), drying: The above mixed raw materials are dried in a dryer, and the drying temperature is 80 to 120 ° C, and the time is 2 to 8 h. (C), Ball: raw material after the drying process using the method of rolling the ball on a disc granulator, disc granulator speed of 400~1600r / mi _n, the size of the sphere is determined by sieving the control, The diameter of the obtained sphere is from 1 mm to 15 mm.

2), preparing the composite sphere:

(d), shell: The powder required for the above proportioning shell is thoroughly mixed in the mixer, the activity of calcium oxide is 200ml, and the mixing time is l~3h. (e) Sphere compounding: The prepared core ball and the shell material are compositely ball-formed on a disc granulator by a rolling method, and the thickness of the outer shell is 0.1 mm to 5 mm, and the size of the sphere is controlled by sieving. The prepared composite sphere size is 1.2mm~25mm. (f), the whole supply is dry: The composite sphere prepared in the above step is dried in a dryer, and the drying temperature is 60 ° C to 120 ° C, and the time is 10 h to 20 h.

Example 3

According to the formula, the core is made of Fe-30%RE master alloy 99%, RE is rare earth strontium-based mixed rare earth, magnesium carbonate 1%; the shell is prepared by mixing 15% water glass with calcium oxide.

1), preparing a core of the composite sphere:

(a) Mixing: The solid raw material required for the above core is crushed and crushed according to the above ratio, and is also ground by micro-pulverization to obtain a particle size of 10 nm to 1.5 mm, and then the powder is mixed. The mixture is thoroughly stirred and mixed, and the mixing time is lh~3h. (b), drying: the above mixed raw materials are dried in a dryer, the drying temperature is 90 ° C ~ 150 ° C, the time is 2h ~ 8h. (c), ball making: The above-mentioned dried raw materials are ball-formed on a disc granulator by a rolling method, and the rotation speed of the disc granulator is 400 to 1600 r/min, and the control of the sphere size is determined by sieving to obtain Ball The diameter of the body is from lmm to 40mm.

2), preparing the composite sphere:

(d), shell: The powder required to take the outer shell according to the above ratio is thoroughly mixed in the mixer, the activity of calcium oxide is 200ml, and the mixing time is lh~3h. (e) Sphere composite: The core ball and the outer shell material are compositely ball-formed on a disc granulator by a rolling method, and the thickness of the outer shell is 0.1 mm to 20 mm, and the size of the sphere is controlled by sieving. The prepared composite sphere size can be 1.2mm~80mm. (f), overall drying: The composite sphere prepared in the above step is dried in a dryer, and the drying temperature is 100 ° C to 200 ° C, and the time is 10 h to 24 h.

Example 4

According to the formula, the core is made of Fe-30%RE master alloy 99%, RE is rare earth strontium-based mixed rare earth, magnesium carbonate 1%; the shell is a mixture of calcium oxide and magnesium oxide (the binder is zero).

1), preparing a core of the composite sphere:

(a) Mixing: The solid raw material required for the above core is crushed and crushed according to the above ratio, and is also ground by air flow micro-grinding to a particle size of lnm~lmm, and then the powder is put into the mixture. The mixture is thoroughly stirred and mixed, and the mixing time is lh~3h. (b) Drying: The above mixed raw materials are dried in a dryer, and the drying temperature is 80 ° C to 100 ° C, and the time is 2 h to 8 h. (c): Ball making: The above-mentioned dried raw materials are ball-made on a ball press by an extrusion method, and the size of the sphere is controlled by sieving to obtain a sphere having a diameter of lmm to 35 mm.

2), preparing the composite sphere:

(d), shell: The powder required to take the outer shell according to the above ratio is thoroughly mixed in the mixer, the activity of magnesium oxide is 200ml, and the mixing time is lh~3h. (e) Sphere compounding: The prepared core ball and the shell material are compositely ball-formed on a disc granulator by a rolling method, and the thickness of the outer shell is 0.1 mm to 20 mm, and the size of the sphere is controlled by sieving. Prepared composite sphere size It can be 1.2mm~75mm. (f), overall drying: The composite sphere prepared in the above steps is dried in a dryer, the drying temperature is 60 ° C ~ 120 C, the time is 101! ~ 24h.

Example 5

The composite sphere of the invention is prepared according to the weight percentage of the following raw materials - 80% of the Fe-30% Ce intermediate alloy is taken according to the formula ratio, 15% of the mixture of calcium carbonate and magnesium carbonate is taken according to 2:1, and the clay is 4%. Water glass 1%; The outer shell is prepared by mixing 10% clay and ordinary cement and a mixture of bentonite and water glass with a mixture of 1:1 calcium oxide and magnesium oxide.

1), preparing a core of the composite sphere:

(a) Mixing: The solid raw material required for the above core is crushed and crushed according to the above ratio, and is also ground and finely ground to achieve a particle size of 1 nm to 1 mm, and then the powder is mixed into the mixture. The mixture is thoroughly stirred and mixed, and the mixing time is lh~3h. (b) Drying: The above mixed raw materials are dried in a dryer, and the drying temperature is 80 ° C to 150 ° C, and the time is 2 h to 5 h. (c), ball making: The above-mentioned dried raw materials are ball-formed on a disc granulator by a rolling method, and the rotation speed of the disc granulator is 400 to 1600 r/min, and the control of the sphere size is determined by sieving to obtain The diameter of the sphere is lmn! ~ 20mm.

2) preparing the composite sphere

(d), shell: The powder required for the outer shell according to the above ratio is thoroughly mixed in the mixer. The activity of calcium oxide and magnesium oxide is 200 ml, and the mixing time is lh~3h. (e) Sphere compounding: The prepared core ball and the shell material are compositely ball-formed on a disc granulator by a rolling method, and the thickness of the outer shell is 0.1 mm to 10 mm, and the size of the sphere is controlled by sieving. The finished composite sphere size is 1.2mn! ~ 40mm can be. (0. Overall drying: The composite sphere prepared in the above step is dried in a dryer, and the drying temperature is 60° (: ~ 150 ° C, time is 10h~24h. Example 6

The composite sphere of the present invention is prepared in the weight percentage of the following raw materials: According to the formulation ratio, the core is made of Fe-30% Nd master alloy 55%, magnesium carbonate 30%, bentonite 10%, water glass 5%; the shell is calcium oxide (the binder is zero).

1), preparing a core of the composite sphere:

(a) Mixing: The solid raw material required for the above core is crushed and crushed according to the above ratio to achieve a particle size of 30 nm to 3 mm, and the powder is placed in a mixer for thorough stirring and mixing. The material time is lh~3h l.5h. (b) Drying: The above mixed raw materials are dried in a dryer, and the drying temperature is 80 ° C to 150 ° C, and the time is 2 h to 8 h. (c)> Ball making: The above-mentioned dried raw materials are ball-formed on a disc granulator by a rolling method. The rotation speed of the disc granulator is 400 to 1600 r/min, and the control of the sphere size is determined by sieving. The diameter of the sphere is lmn! ~ 30mm.

2), preparing the composite sphere:

(d), shell: The powder calcium oxide required for the outer shell, the activity of calcium oxide is 200ml, the mixing time is lh~3h, (e), the sphere compound: the prepared core sphere and shell The raw materials are compositely ball-formed on a disc granulator by a rolling method, and the thickness of the outer casing is 0.1 mm to 15 mm. The size of the sphere is controlled by sieving, and the prepared composite sphere has a size of 1.2 mm to 60 mm. (f), overall drying: The composite sphere prepared in the above step is dried in a dryer, and the drying temperature is 70 ° C to 150 ° (:, the time is 10 h to 24 h.

Example 7

According to the formula, the core is made of Fe-30% La intermediate alloy 65%, calcium carbonate 25%, ordinary cement 2%, bentonite 8%; the shell is prepared by mixing 8% bentonite with calcium oxide.

1), preparing a core of the composite sphere -

(a), compounding: crushing and crushing the solid raw materials required for the above core according to the above ratio The particle size is from 50 nm to 2.5 mm, and the powder is placed in a mixer for thorough stirring and mixing, and the mixing time is from 1 h to 3 h. (b) Drying: The above mixed raw materials are dried in a dryer, and the drying temperature is 110 ° C to 150 ° C, and the time is 2 h to 6 h. (c), ball making: The above-mentioned dried raw materials are ball-formed on a disc granulator by a rolling method, and the rotational speed of the disc granulator is 400 to 1600 r/min, and the control of the sphere size is determined by sieving to obtain The diameter of the sphere is lmm~ 8mm o

2), preparing the composite sphere:

(d), shell: The powder required to take the shell according to the above ratio is thoroughly mixed in the mixer. The activity of calcium oxide is 200ml, and the mixing time is 11! ~ 3h. (e) Sphere compounding: The prepared core ball and the shell material are compositely ball-formed on a disc granulator by a rolling method, and the thickness of the outer shell is 0.1 mm to 20 mm, and the size of the sphere is controlled by sieving. The prepared composite sphere size can be 1.2mm~48mm. (f), overall drying: The composite sphere prepared in the above step is dried in a dryer, and the drying temperature is 80 ° C to 180 ° C, and the time is 10 h to 24 h.

Example 8

According to the formulation ratio, the core is made of Fe-30%Gd master alloy 70%, according to 1:1, calcium carbonate and magnesium carbonate 20%, clay 7%, water glass 3%; shell contains 20% clay and calcium oxide and The magnesium oxide mixture is prepared by mixing.

1), preparing a core of the composite sphere:

(a) Mixing: The solid raw material required for the above core is crushed and crushed according to the above ratio, and is also ground by a gas flow micro-grinding to a particle size of 5 nm to 1 mm, and then the powder is mixed into the mixture. The mixture is thoroughly stirred and mixed, and the mixing time is lh~3h. (b), drying: the above mixed raw materials are dried in a dryer, the drying temperature is 90 ° C ~ 120 ° C, the time is 2h ~ 8h. (c), ball making: The above-mentioned dried raw materials are made into a ball on a disc granulator by a rolling method, and the disc is made. The rotation speed of the pelletizer is 400 to 1600 r/min, and the control of the sphere size is determined by sieving, and the diameter of the sphere is obtained from 1 mm to 30 mm.

2) preparing the composite sphere

(d), shell: The powder required for the outer shell according to the above ratio is thoroughly mixed in the mixer. The activity of calcium oxide and magnesium oxide is 200 ml, and the mixing time is lh~3h. (e) Sphere compounding: The prepared core ball and the shell material are compositely ball-formed on a disc granulator by a rolling method, and the thickness of the outer shell is 0.1 mm to 10 mm, and the size of the sphere is controlled by sieving. The finished composite sphere size is 1.2mn! ~ 50mm can be. (f), overall drying: The composite sphere prepared in the above step is dried in a dryer, and the drying temperature is 80 ° C ~ 150 ° C, the time is 101! ~ 24h. Example 9

According to the formula, the core is made of Fe-30%Sm master alloy 60%, calcium carbonate 30%, clay 7%, water glass 3%; the shell is magnesium oxide (the binder is zero).

1), preparing a core of the composite sphere:

(a) Mixing: The solid raw material required for the above core is crushed and crushed according to the above ratio to achieve a particle size of 90 nm to 3.5 _m , and the powder is placed in a mixer for thorough stirring and mixing. The mixing time is 11! ~ 3h. (b) Drying: The above mixed raw materials are dried in a dryer, and the drying temperature is 90 ° C to 120 ° (:, the time is 2 1! ~ 7 h. (c), ball making: The above-mentioned dried raw materials are ball-formed on a disc granulator by a rolling method, and the rotational speed of the disc granulator is 400 to 1600 r/min, and the control of the sphere size is determined by sieving, and the diameter of the sphere is obtained as lmm~ 25mm.

2), preparing the composite sphere:

(d), shell: The powder magnesium oxide required for the outer shell is used, the activity of magnesium oxide is 200m, and the mixing time is lh~3h. (e) Sphere compounding: Rolling the prepared core sphere and shell material The method is to perform composite ball making on a disc granulator. The thickness of the outer casing is 0.1 mm to 10 mm. The size of the sphere is controlled by screening, and the prepared composite sphere has a size of 1.2 mm to 45 mm.

(f), overall drying: The composite sphere prepared in the above step is dried in a dryer, and the drying temperature is 90 ° C to 150 ° C, and the time is 10 h to 24 h.

Example 10

According to the formula, the core is made of Fe-30%Sm intermediate alloy 30%, calcium carbonate 60%, ordinary cement 6 %, water glass 4%; the outer shell is prepared by mixing 10% bentonite with magnesium oxide.

1), preparing a core of the composite sphere:

(a) Mixing: The solid raw material required for the above core is crushed and crushed according to the above ratio, and is also ground by micro-grinding to obtain a particle size of 10 nm to 0.08 mm, and then the above powder is mixed. The mixture is thoroughly stirred and mixed, and the mixing time is lh~2h. (b:), drying: The above mixed raw materials are dried in a dryer, and the drying temperature is 80'C~120 °C, and the time is 2h~5h. (c), ball making: The above-mentioned dried raw materials are ball-formed on a disc granulator by a rolling method, and the rotation speed of the disc granulator is 400 to 1600 r/min, and the control of the sphere size is determined by sieving to obtain The diameter of the sphere is lmn! ~ 10mm.

2), preparing the composite sphere:

(d), casing: The powder required to take the outer casing according to the above ratio is thoroughly mixed in the mixer, and the activity of magnesium oxide is 200 ml. Mixing time is lh~3h (e), ball composite: The prepared core ball and the shell material are compositely ball-formed on a disc granulator by rolling method, and the thickness of the outer shell is 0.1mm~15mm, and sieved The size of the sphere is controlled and determined, and the size of the prepared composite sphere is 1.2 mm to 40 mm. (f), overall drying: The composite sphere prepared in the above step is dried in a dryer, and the drying temperature is 70 ° C to 160 ° C, and the time is 10 h to 24 h.

Example 11 The composite sphere of the present invention is prepared in the weight percentage of the following raw materials:

According to the formula, the core is made of Fe-18%B intermediate alloy 10%, calcium carbonate 70%, clay 20%; the outer shell is prepared by mixing 2% ordinary cement with calcium oxide.

The preparation method of the composite sphere of the present invention is the same as that of the example 1, and will not be described.

Example 12

According to the formula, the core is made of Fe-30% La intermediate alloy 5%, calcium carbonate 65%, ordinary cement 28%, bentonite 2%; the outer shell is prepared by mixing 20% bentonite with calcium oxide.

The preparation method of the composite sphere of the present invention is not described in the same manner as in Example 7.

The composite sphere prepared by the above method for controlling the precise addition of trace elements in steel is dried and then cooled into an ultra-thin high-strength polyethylene plastic bag, and the weight of each bag is 10 kg ~ 30 kg / bag, and the packaging is ensured. Sealed well, protected from moisture, and used within 20 days.

Claims

Rights request

A composite sphere for controlling the precise addition of trace elements in steel, characterized in that the core of the composite sphere comprises: a trace element and a swelling agent, and the outer shell of the composite sphere is composed of calcium oxide, magnesium oxide or calcium oxide. A mixture of magnesium oxide.

2. The composite sphere for controlling the precise addition of trace elements in steel according to claim 1, wherein the core of the composite sphere is prepared from the following raw materials in a percentage by weight - trace elements 0.1% to 99%

Expansion agent 1%~70%

Binder 0~30%

3. The composite sphere for controlling the precise addition of trace elements in steel according to claim 1, wherein the core of the composite sphere is mainly prepared by weighting the following raw materials:

Trace elements 30%~80%

Expansion agent 8%~55 %

Binder 5 %~15 %

4. The composite sphere for controlling the precise addition of trace elements in steel according to claim 1, wherein the outer shell of the composite sphere further comprises 0 to 20% of a binder.

5. The composite sphere for controlling the precise addition of trace elements in steel according to claim 1, 2 or 3, characterized in that the trace elements comprise: Fe-18% B intermediate alloy, Fe-30% RE intermediate alloy.

6. The composite sphere for controlling the precise addition of trace elements in steel according to claim 5, wherein RE in the Fe-30%RE master alloy is rich in Ce, La mixed rare earth, rich in Ce, Nd Any one of rare earth or pure rare earths Ce, Nd, La, Gd, and Sm is mixed.

7. The compound for controlling the precise addition of trace elements in steel according to claim 1, 2 or 3 A spheroid, characterized in that the expansion agent is composed of a mixture of calcium carbonate, magnesium carbonate, calcium carbonate and magnesium carbonate.

8. The composite sphere for controlling the precise addition of trace elements in steel according to claim 2, 3 or 4, characterized in that the binder is any one of clay, ordinary cement, bentonite and water glass or Two or more.

9. A method of making a composite sphere according to claim 1 wherein the method comprises the following steps:

1), preparing a core of the composite sphere -

(a) Mixing: The solid raw material required for the core is crushed and crushed according to the ratio, so that the particle size is Inn! ~ 3.5mm, then put the above powder and binder into the mixer for thorough mixing and mixing, the mixing time is 1 h~3h.

(b) Drying: The above mixed raw materials are dried in a dryer, and the drying temperature is 80 ° C to 150 ° C, and the time is 2 h to 8 h.

(c), ball making: The ball after the above drying process is made into a ball through a ball making device, and the diameter of the ball is lmn! ~ 40mm _o

2), preparing the composite sphere:

(d), shell: According to the ratio, the powder required for the outer shell is thoroughly mixed in the mixer. The activity of calcium oxide and magnesium oxide is 200 ml, and the mixing time is lh~3h.

(e) Sphere compounding: The prepared core ball and the shell material are compositely ball-formed on a ball making machine by a rolling method. The thickness of the outer casing is 0.1 mm to 20 mm, and the prepared composite sphere size is 1.2 mn! ~ 80mm can be.

(0. Overall drying: The composite sphere prepared in the above step is dried in a dryer, and the drying temperature is 60 ° C to 200 ° C, and the time is 101! ~ 24 h.