JP2003105520A - Lance tip for metallurgical use, and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lance tip which can be stably used for a long time while the lance function is left unchanged by forming a film of high hardness, excellent wear resistance and heat resistance, and high heat conductivity on an outer surface of the lance tip. SOLUTION: In the lance tip for metallurgical use, a carbide cermet thermally sprayed film is formed to the thickness of 30-300 μm on an outer surface of the water-cooled lance tip fitted to a tip of a lance pipe with an undercoat of a heat-resistant metal interposed if necessary.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lance tip attached to the tip of a metallurgical lance pipe used for operations such as melting, decarburization and dephosphorization of steel. It can also be used as a lance chip for melting and refining.

[0002]

2. Description of the Related Art As a lance for blowing oxygen gas used in melting furnaces and decarburizing furnaces used in the steelmaking and steelmaking stages in ironmaking plants, in addition to excellent wear resistance and heat resistance, hot metal, The property that molten iron such as molten steel is hard to adhere is required. In particular, the adhesion of molten iron to the surface and its growth phenomenon may make it impossible to move the lance up and down, which is a very important problem in continuous operation. As a countermeasure against this,
Selection of material that does not allow molten iron to adhere (JP-A-4-88108), control of surface roughness (JP-A-3-120544),
Techniques such as construction of various surface treatment films have been proposed. For example, looking at a thermal spray coating that belongs to the technical field of the present invention, (a) an example in which an oxide ceramic coating such as Al ₂ O ₃ and Cr ₂ O ₃ is applied (Japanese Patent Laid-Open No. 59-23827, Sho 6
3-183254, JP-A-3-96342), (b) oxide cermet coating (JP-A-59-43811), an example of applying a nitride cermet coating (JP-A-8-199221) )
Have been proposed.

In the case of oxide ceramics, for example, the formation of the above-mentioned thermal spray coating has heat resistance and the property that molten iron does not easily adhere, but on the other hand, it is weak in mechanical and thermal shock resistance and often peels off during work. There was a drawback. Therefore, up to now, no thermal spray coating has been developed that completely satisfies the required performance.

[0004]

By the way, a copper cap called a lance tip is attached to the tip of the lance pipe so that a large amount of oxygen gas can be efficiently sprayed during operation. ing. However, such a lance tip, in addition to receiving strong radiant heat from molten iron in a high temperature state, sometimes ejects oxygen gas containing various fine powders, so heat resistance and wear resistance are particularly required. is there. To meet such requirements of lance tips, heat resistant alloys (JIS H8303 self-fluxing alloy) and Al ₂ O have conventionally been used on the outer surface of the lance tips.
Techniques for coating and spraying oxide-based ceramic coatings such as ₃ , ZrO ₂ and Cr ₂ O ₃ have been proposed (Shokaisho 63-
No. 85649). However, even if these known techniques are applied, the life of the lance tip is still short, and the lance tip is often forced to be replaced during operation, which results in a decrease in productivity.

Therefore, an object of the present invention is to coat the outer surface of the lance tip with a film having a high hardness, excellent wear resistance and heat resistance and a high thermal conductivity so that the lance function does not change forever. It is to propose a lance tip that can be used stably for a period of time.

[0006]

[Means for Solving the Problems] In the research for realizing the above object, the inventors of the present invention, in particular, directly or undercoat a heat-resistant alloy on the exposed outer surface of the water-cooled lance tip. Forming a carbide cermet thermal spray coating indirectly through improves the heat resistance and wear resistance. If the construction conditions of the carbide cermet thermal spray coating are controlled, only good adhesion with the lance tip can be obtained. In addition, it has a high thermal conductivity, can maintain the water cooling effect of the chip more effectively, and has a hard coating that can withstand the collision of molten iron particle agglomerates and the abrasion effect of lime powder contained in oxygen gas. And prevent the tip shape (oxygen gas outlet) from being deformed,
Being able to continue efficient operating conditions for a long period of time, and when the surface of the carbide cermet sprayed coating is polished to increase its smoothness, physical adhesion of molten iron particles and their growth are effectively prevented. It was discovered that it is possible.

The present invention, which was developed based on such knowledge, has 30 to 300 carbide cermet spray coating on the outer surface of the water-cooled lance tip attached to the tip of the lance pipe.
This is a metallurgical lance tip having a basic structure of a coating formed to a thickness of μm.

Further, according to the present invention, an undercoat sprayed coating of a heat-resistant alloy is formed to a thickness of 30 to 200 μm on the outer surface of a water-cooled lance tip attached to the tip of a lance pipe, and then a carbide cermet is further formed thereon. The lance tip for metallurgy may be characterized in that the top coat sprayed coating is formed to a thickness of 30 to 300 μm.

In the present invention, the carbide cermet
Spray coating of WC, Cr₃C₂, Cr ₇C₃, Cr_{twenty three}C₆, TiC,
VC, SiC, B_FourAny one selected from C, TaC and ZrC
60-95mass%, Ni, Cr, Co of one or more carbides
And one or more metals selected from Al and Al
Composite powder containing 40 to 5 mass% of alloy consisting of the above metals
Being formed by spraying powdered material, underco
Heat-resistant alloy for steel is selected from Ni, Cr, Co, Al and Y
Is an alloy containing two or more kinds of metals.
This is a preferred embodiment.

In the above metal-cooled lance for metallurgy, a carbide cermet is sprayed on the outer surface of a lance tip attached to the tip of a water-cooled lance pipe under the condition that the flight speed of spray particles in a spray heat source is 250 m / s or more. , Film thickness 30-300
It can be manufactured by forming a sprayed coating of μm.

As another method, on the outer surface of the lance tip attached to the tip of the water cooling lance pipe,
First, after forming a thermal spray coating of a heat-resistant alloy as an undercoat, a carbide cermet as a topcoat is sprayed on the undercoat under the condition that the flight speed of the spray particles in the thermal spray heat source is 250 m / s or more, and the film thickness 30 to 300
This is a method of forming a composite sprayed coating of μm.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The first basic feature of the present invention is to coat the outer surface of a water-cooled lance tip detachably attached to the tip of a water-cooled lance pipe with a carbide cermet spray coating. In the present invention, the reason for paying attention to the carbide cermet sprayed coating is that the carbide is generally hard in the first place and has high thermal conductivity, so that when it is formed on the outer surface of the lance tip, it exhibits good wear resistance and a water cooling effect. Is large, the temperature of the lance tip surface can be kept low. However, it is difficult to form a good coating with a single carbide because it does not exhibit a molten state like metal during thermal spraying. Therefore, in the present invention, with respect to this carbide, a heat-resistant metal, for example, Ni, C
Cermet powder containing 5 to 40 mass% of any one metal selected from r, Co, Al, and Y or an alloy composed of two or more metals is used. On the other hand, as carbides, WC, Cr ₃ C ₂ , Cr ₇ C ₃ , Cr ₂₃ C ₆ , TiC, VC, SiC, B ₄ C, T
Any one or two selected from aC and ZrC
About 60 to 95 mass% of carbides of at least one kind is blended.

As another embodiment of the present invention, a composite thermal spray coating may be formed by laminating and coating the above-mentioned carbide cermet thermal spray coating on an undercoat using a heat resistant alloy. As the heat resistant alloy for the undercoat, it is preferable to use an alloy composed of two or more kinds of metals selected from Ni, Cr, Co, Al and Y.

The carbide cermet sprayed coating is formed directly on the outer surface of the lance tip, and an undercoat of a heat resistant alloy is preferably applied in advance by a spraying method,
In any case where the above-mentioned carbide cermet is sprayed as a top coat onto the undercoat to form a composite coating, the thickness of the carbide cermet spray coating itself is either a single layer or a composite coating. , 30 to 300 μm is preferable. The reason for this is that if the thickness is less than 30 μm, the porosity will be high and uniform film formation will not be possible. On the other hand, even if the thickness is more than 300 μm, the effect is saturated, which is economically disadvantageous. The thickness of the undercoat is also preferably about 30 to 250 μm. The reason is that if the film thickness is 30 μm or less, uniform film formation is difficult, while if it is 250 μm or more, the water cooling effect on the carbide cermet spray coating of the top coat is diminished, which is not preferable.

In the present invention, it is desirable to limit the porosity of the above-mentioned carbide cermet spray coating in order to keep the surface temperature low. In general, some of the above-mentioned carbides are oxides (WO
3) is generated and consumed, and the binding force of the WC particles constituting the film is reduced, so that the particles locally fall off and become rough, and molten iron may easily adhere. Therefore, it is desirable to keep the surface temperature of the carbide cermet sprayed coating as low as possible. As a countermeasure against this, in the present invention, attention is paid to the porosity of the thermal spray coating to prevent the decrease in thermal conductivity due to the presence of the air layer contained in the coating. Therefore, in the present invention, the heat source of the high-speed flame spraying method and the explosive spraying method is used as the spraying method, and the flight speed of the carbide cermet spraying material particles flying in the heat source,
The porosity is as low as 1.5% or less by constructing the lance tip at a speed of 250 m / s or more so as to pierce it with strong kinetic energy and changing a part of the kinetic energy into heat energy. In addition, it was decided to form a high thermal conductive thermal spray coating with high adhesion and low oxide content.

The thermal conductivity of the Cr ₃ C ₂ -20Ni-5Cr thermal spray coating formed by adopting such thermal spraying conditions is 5 W / m · K, and the metallic system having a porosity of 2 to 5% (for example, 50Ni-Gr
(Alloy) It was found to be much higher than 2.5 W / mK of the spray coating, and therefore the water cooling effect of the lance tip can be used more effectively, and the coating surface temperature covering the lance tip surface is always 200 ° C or less. Will be able to hold.

In the present invention, it is also preferable that the surface roughness of the carbide cermet sprayed coating is such that molten iron does not easily adhere thereto. As described above, in the present invention, due to the excellent water cooling effect, the temperature of the carbide cermet sprayed coating formed on the surface of the lance tip is kept low. Therefore, the opportunity for the molten iron particles to adhere due to spitting or the like increases. In this regard, according to the knowledge of the inventors, it is known that the surface roughness of the sprayed coating has a great influence on the deposition rate of molten iron particles. Therefore, the inventors have experimentally determined the relationship between the material strength of the thermal spray coating and the adhesive force of the molten iron particles due to the difference in surface roughness, and as described in detail in Examples, for the carbide cermet thermal spray coating, It was effective to finish the surface roughness Ra to 3.0 μm or less, and it was confirmed that the adhesive force of the molten iron particles was remarkably reduced by this. In finishing the surface roughness of the spray coating, in the case of a spray coating having a high porosity, the pores become pits and remain on the surface,
Since it has been confirmed that this facilitates the adhesion of molten iron particles, as described above, the formation of a sprayed coating with a small porosity (≦ 1.5%) will also be advantageous in terms of such surface finishing. .

Next, the manufacturing method of the present invention will be described.
One of the characteristics required for the film formed on the outer peripheral surface of the tip of the lance pipe is improvement in wear resistance and thermal shock resistance. In this respect, in the present invention, since a carbide cermet thermal spray coating containing a carbide as a main component is used, it has extremely high hardness as compared to copper which is a lance tip base material, and contact with lime particles or molten iron particles during operation, It also exerts a strong resistance to the abrasion effect caused by a collision. Such a thermal spray coating needs to be formed, for example, by a high-speed flame thermal spraying method in an air atmosphere under high-speed thermal spraying conditions such that the flight speed of thermal spray particles is 250 m / s or more. Films formed under such thermal spraying conditions, for example, a thermal sprayed coating of WC-12mass% Co, HV: 950-1150, WC-20mass% Ni-5mass% Cr
In the thermal spray _{coating, HV: 850~950, Cr 3 C} 2 -20mass% Ni-5
With a mass% Cr sprayed coating, HV: 650-850 is exhibited. Moreover, under the environment in which the lance is used, thermal shock due to the adhesion of molten iron particles at about 1500 ° C. is continuously applied, but even in this case, the results of experiments conducted by the inventors or the results of use in an actual machine environment indicate that Since the lance may be water-cooled, it has been confirmed that it has sufficient thermal shock resistance.

[0019]

Example (Example 1) In this example, a copper test piece (JIS H 3100 standard C1002P) identical to the chip material, width 50 mm x length
Electric furnace with 100 to 150 μm thick metal spray coating, oxide ceramic spray coating, and carbide cermet spray coating directly on one side of 100 mm × 5 mm thickness
After heating in (500 ° C. × 15 minutes), the operation of putting into water at 25 ° C. was repeated 10 times, and the thermal shock resistance of the thermal spray coating was investigated.

Table 1 shows the results of this test. From this result, the following is considered. Although the metal-based sprayed coating shows relatively good adhesion, the volume expansion effect due to the oxidation of the copper base material by the air invading the pores of the coating and the vaporization of the invading water as the test is repeated. As a result, local peeling occurs. Most oxide-based ceramic sprayed coatings peel off immediately after thermal spraying, and were easily peeled off by heating once.
Then, when an 80Ni-20Al alloy was formed as an undercoat (50 μm) and then applied as a topcoat thereon, the oxide films of Nos. 4, 5, and 6 showed good adhesion. From these results, it was found that the thermal spraying of oxide-based ceramics required the application of a metal-based undercoat. However, the construction of the undercoat may raise the film temperature of the topcoat and accelerate the wear of the topcoat. Since the carbide cermet spray coating is formed by piercing a copper substrate sharply, it exhibits excellent adhesion and strong interparticle bonding force, and the surface of No. 7 88WC-12Co coating discolors slightly. However, it was confirmed that it can withstand 10 thermal shock tests.

[0021]

[Table 1]

Example 2 In this example, the wear resistance of each thermal spray coating of metal, oxide ceramics and carbide cermet formed on the surface of a copper test piece was investigated. (1) Test copper plate: JIS H 3100 standard C1020P (Dimension: width 50 mm
(Length x 100 mm x thickness 5 mm) (2) Test film: Using the above copper plate as a base material, one side of which is metal-based: 13Cr steel, Ni-20Cr 200 μm Oxide-based: Ni-20Cr is an undercoat (100 μm),
Thereon _{Al 2 O 3, Al 2 O} 3 -50Cr 2 O 3 to 150μm carbide Cermet: WC-12Co-5Cr WC- 2Cr 3 C 2- 20Ni-5Cr the numbers above indicates a mass%. (3) Abrasion test method This abrasion test was performed by the test method as shown in FIG. That is, 70 g of Al ₂ O ₃ powder was obliquely (tilt angle 45
1000 mm in height on the thermal spray coating test piece 2 placed at (°)
Repeat the operation of colliding by gravity from the position of 20 mm through the steel pipe 1 with a diameter of 20 mm, and then compare the wear resistance of the coating, more accurately the blast erosion resistance, from the weight measurement results of the coating test piece before and after the test. It was done by the method. In the figure, reference numeral 3 is the surface of the test spray coating, 4 is a funnel, 5 is Al ₂ O ₃ powder, and the dotted line shows the falling direction of Al ₂ O ₃ powder.

Table 2 shows the results. As is clear from this result, the metal spray coating (No.
1, 2) had the largest weight loss, followed by oxide-based ceramic sprayed coatings (No. 3, 4). In contrast,
The carbide cermet spray coating according to the present invention has a weight loss of 50 to 70 mg, which corresponds to 18 to 32% of the metal spray coating and 53 to 75% of the oxide ceramic spray coating, and has excellent blast erosion resistance. Was confirmed.

[0024]

[Table 2]

(Embodiment 3) In this embodiment, a lance tip having a sprayed coating conforming to the present invention was attached to the tip of a water-cooled lance pipe of an actual steel melting furnace, and the performance in a practical environment was investigated. In this embodiment, the following thermal spray coating is formed directly on the externally exposed surface of the lance tip by a high speed flame thermal spraying method. (1) WC-12mass% Co 150μm (2) 20Cr-8Al-15Co-0.5Y-Remaining Ni (mass%) undercoat 80μm Cr ₃ C ₂ -20Ni-5Cr (ma
ss%) 150 μm In the operation of the melting furnace in this example, the untreated copper lance tip was replaced by continuous use for 90 hours, but the lance tip formed with the sprayed coating of the present invention was operated for 270 hours continuously. It has been found that it maintains a healthy state even when used, and exhibits excellent functions even in a practical environment. In addition, as a comparative example, the Al ₂ O ₃ -50Cr ₂ O ₃ thermal spray coating illustrated in Example 2 was used.
When (No. 4 in Table 2) was similarly used, the thermal spray coating itself showed a healthy state, but cracks easily occurred due to thermal shock during operation and impact of molten iron particle lumps, A phenomenon of local peeling was observed, and it could not be used in a stable state for a long period of time.

[0026]

As described above, a cermet thermal spray coating of carbide is directly formed on the surface of the lance tip attached to the tip of the water cooling lance, or indirectly formed by laminating an undercoat of a heat resistant alloy, Their surfaces
Ra: When adjusted to a roughness of 3.0 μm or less, it has high hardness, good adhesion, and high thermal conductivity, so it can withstand abrasion due to collision of molten iron in a practical environment, and adheres and melts molten iron particles. It can exert the effect of remarkably suppressing the growth. In particular, it has a strong resistance to abrasion due to various powder materials added by being included in oxygen gas during molten steel treatment, and is effective in improving the chip life.
As a result, the lance tip provided with the carbide cermet sprayed coating of the present invention can maintain stable gas / powder-granule ejection conditions for a long period of time. It is possible to control the expense expenditure by making it into a consumable item, and contributes to the improvement of productivity and the cost reduction.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a drop-type wear test device for Al ₂ O ₃ powder used in Examples.

[Explanation of symbols]

1 Steel tube 2 Thermal spray coating test piece 3 Thermal spray coating surface 4 Funnel 5 Al ₂ O ₃ powder

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masayuki Okitsu             1 to 14 Minami-Futami, Futami-cho, Akashi-shi, Hyogo             ー Caro Corporation Akashi Factory (72) Inventor Hashimoto             1 to 14 Minami-Futami, Futami-cho, Akashi-shi, Hyogo             ー Caro Corporation Akashi Factory (72) Inventor Riichi Aoki             1 Fuji-machi, Hirohata-ku, Himeji-shi, Hyogo New Japan             Hirohata Works, Ltd. (72) Inventor Takeshi Morita             1 Fujimi, Hirohata-ku, Himeji-shi, Hyogo New Japan             Hirohata Works, Ltd. F-term (reference) 4K031 AA04 AB02 AB03 CB21 CB32                       CB37 CB45 DA01 DA08                 4K070 CF04

Claims (6)

[Claims] 1. A metallurgical lance tip characterized in that a water-cooled lance tip detachably attached to the tip of a lance pipe has a carbide cermet thermal spray coating with a thickness of 30 to 300 μm on the outer surface thereof. 2. A water-cooled lance tip detachably attached to the tip of a lance pipe has an undercoat sprayed coating of a heat-resistant alloy having a thickness of 30 to 200 μm on the outer surface of the water-cooled lance tip. A lance tip for metallurgy, comprising a composite coating in which a topcoat sprayed coating of a carbide cermet having a thickness of 300 µm is laminated and coated. 3. The thermal spray coating of the carbide cermet is 60
~ 95mass% WC, Cr ₃C₂, Cr₇C₃, Cr_{twenty three}C₆, TiC, VC, Si
C, B_FourOne or more selected from C, TaC and ZrC
From the above carbides and 40-5 mass% Ni, Cr, Co and Al
Consists of any one metal or two or more selected
Formed by spraying a composite powder material composed of an alloy and
It is a thing, The thing of Claim 1 or 2 characterized by the above-mentioned.
Lance tip. 4. The heat resistant alloy for undercoat comprises Ni, Cr,
The lance tip according to claim 2, which is an alloy containing two or more kinds of metals selected from Co, Al and Y. 5. A carbide cermet is provided on the outer surface of a lance tip detachably attached to the tip of a water-cooled lance pipe, and the flight speed of spray particles in a spray heat source is 250 m /
A method for producing a metallurgical lance tip, which comprises spraying under a condition of s or more to form a sprayed coating of a carbide cermet having a film thickness of 30 to 300 μm. 6. A heat-resistant alloy sprayed coating is first formed as an undercoat on the outer surface of a lance tip detachably attached to the tip of a water-cooled lance pipe, and then a carbide cermet is formed as a topcoat on the undercoat. The flight speed of the spray particles in the spray heat source is 250
A method for manufacturing a metallurgical lance tip, which comprises spraying under a condition of m / s or more to form a composite sprayed coating having a film thickness of 30 to 300 μm.