JPS5964712A - Method of addition for obtaining alloy - Google Patents

Abstract

PURPOSE:To perform the titled addition with a high yield without segregation, in adding Mo or W to molten steel, by blowing an oxide of Mo or W together with carrier gas through a dipping lance into the molten steel. CONSTITUTION:The mixed body of powdery MoO3 or CaWO4 with carrier gas, e.g. air, is blown into molten steel 3 through the top end of a lance 2 immersed in the molten steel 3 having slag 4 inside a furnace 1, and the dispersion zone 6a or 6b of said mixed body is formed inside the molten steel 3. At this time, if the mixing ratio is below about 30wt%, said dispersion zone exhibits such a shape as shown in the zone 6a, so that the part 7 of the dispersed powdery body rises up without completely reducing it with Si, etc. in the molten steel. On the other hand, in the range of a pref. mixing ratio, the powdery body is deeply dispersed in such a state as shown in the zone 6b into the molten steel 3, so that the molten steel 3 is suifficiently agitated by the thermal expansion and floatation of air, and the powdery body of larger specific gravity is dispersed into a larger range so as to increase the chance to meet with Si, etc. in the molten steel. Consequently, even a volatile powdery body is rapidly reduced, and Mo or W is uniformly diffused into the entire body of the molten steel by the effect of agitation caused by the injection of air without the formation of segregation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for efficiently adding KMo and W to molten steel with good yield.

Mo and W are essential as additive elements for structural steel, tool steel, die steel, etc., but are expensive alloying elements. Therefore, the quality of the yield when Mo and W are added to molten steel directly affects the manufacturing cost and product price of the steel.

Conventionally, the method of adding expensive Mo and W to molten steel is to supply an inert gas such as Ar into molten steel through a porous plug installed at the bottom of a container such as a converter, electric furnace, or ladle. However, while stirring the molten steel, a single metal such as Mo or 'W or a ferroalloy of MO or W is directly added to the surface of the molten steel, or a method in which it is continuously added in the form of a rod (called the wire feeder method). A commonly used method is to fill alloy additives in a cannonball-shaped container or the like and throw it into molten steel (referred to as bombardment).

However, in such conventional methods, there is a quantitative restriction on the amount of inert gas supplied from the bottom of the container, dust, insufficient stirring of the molten steel, and the addition metal has a high melting point and is in the form of lumps or granules. There were problems in that the dissolution time became long, the yield was poor, and segregation was likely to occur.

Furthermore, when Mo and W oxides are added from the surface of the molten steel, the yield of reduction and recovery is low, which poses a problem in terms of manufacturing costs.

Furthermore, since the elemental metals of Mo and W, the ferroalloys of Mo and W, and the oxides of Mo and W are all expensive, improving their addition yield is an extremely important technical issue from the perspective of reducing the manufacturing cost of steel. There is an urgent need to develop it.

The present invention was made to solve the problems of the conventional method, and an object of the present invention is to provide a new method that can add Mo and W to molten steel with a high yield and without segregation.

In the conventional method, the main reason for the poor yield when Mo and W oxide powders are added to molten steel is that molybdenum oxide (Mo5
3), and to a slightly lesser extent, it was found that oxidation causes evaporation and loss before being reduced and recovered in the molten steel, and the stirring power of the molten steel is low.

The present invention is based on the above knowledge, and MO, W in molten steel.
In addition, powder or granules made of the oxides of Mo and W are blown into the pre-molten steel together with a carrier gas through a lance immersed in the molten steel.

The present invention will be explained in detail below.

In carrying out the present invention, all furnaces or vessels operated with alloy addition, such as a converter furnace, an X-air furnace, an AOD furnace, or a ladle, are included in addition to the ordinary arc electric furnace. Mo in molten steel
, W f is added in the form of a raw material such as an oxide such as MoO3 or C&Wo4 (referred to as celite). The oxides such as MoO3 and CaWO4 are required to be in the form of powder or granules so that they can be easily transported under high pressure by a carrier gas.

In the present invention, the above M003. A method of mixing oxide powder or granules such as CaWO4 with a carrier gas and injecting the mixture at high pressure into molten steel from a lance located near the bottom of the molten steel to stir the molten steel and simultaneously add ~Io, W. adopt. At this time, the carrier gas is Ar, He
In addition to an inert gas such as pN2, air or a mixture thereof may be used. While inert gases are expensive and have limited supply, Ar and N2 can be used as carrier gases.
If an inert gas such as Ar is used, Ar or the like will thermally expand and rise rapidly in the molten steel without reacting with the elements in the molten steel, which may instead cause splash.

It is preferable to use air, which is an inexhaustible resource, as the carrier gas from the viewpoint of reducing manufacturing costs. Even if air is used as the carrier gas, the amount of oxygen supplied to #steel is negligible because it is minute compared to the amount of acid that enters the molten steel from MoO3pCaW04. And since it is an oxide, there is no worry about oxidation loss. □ In the present invention, it is more preferable that the mixing ratio of the powder or granules made of the oxides of M, O, and W to the carrier gas is 30% by weight or more and 50% by weight or less.

Well, the weight of powder, etc. injected per unit time is w,
(Ky/mjn), and the weight of the injected carrier gas per unit time υ is W, (Kp/min),
The above mixing ratio (μB) is expressed by the following formula.

μB = W8/~Va (1) Figure 2 shows an example of the relationship between the mixing ratio (μB) and the reduction yield of Mo and W, with the horizontal axis representing the mixing ratio and the vertical axis representing Mo. , shows the reduction yield of W.

(As shown in A, if the mixing ratio (μB) is less than 30% by weight, the yield of % [o, W] cannot be improved, and the blowing time becomes longer, causing melting and fatigue of the immersion lance, which makes the operation difficult. On the other hand, if it exceeds 50% by weight, the hose that transports the mixture is likely to clog and pulsate, making operation difficult and reducing the yield.At the above mixing ratio, the added powder is mixed with the carrier gas, The molten steel is injected through a lance immersed near the bottom of the interior.The shape, dimensions and number of immersion lances are determined by taking into account the furnace model, the weight of molten steel in the furnace, the injection area, etc. Although the angle varies depending on the furnace type, it is preferably about 25 to 35 degrees with respect to the horizontal.

In addition, the blowing time is set to the predetermined M required for adding Mo and W alloys.
It is determined by the supply amount of oO2 and CaWO4, the blowing speed, the reduction recovery yield, etc.

The manner in which the mixture of MoO2, CaWO, powder and carrier gas is blown will be explained with reference to FIG. 3 attached hereto.

In the figure, 1 is a furnace, 2 is an immersion lance, 6 is molten steel, and 4 is slag. A mixture of Mobs, CaWO4 powder, and carrier gas is transported under high pressure through the transport pipe 2a and blown into the molten steel 6 from the tip of the immersion lance 2 located near the bottom of the molten steel 6. Dispersion zones 6a and 6b of the mixture are then formed in the molten steel 3. At this time, the shape appears like a dispersion zone 6a where the mixing ratio is less than 30% by weight, and the dispersed powder is less than the reducing element in the molten steel near the dispersion zone 6a.
St> etc., it is not completely reduced and a portion 7 rises to the layer of slag 4 on the molten steel. Therefore, the yield of reduction and recovery of Mo and W deteriorates. On the other hand, in a more preferable mixing ratio range according to the method of the present invention, the molten steel is deeply dispersed in the molten steel 6 like the dispersion zone 6b, and the molten steel is sufficiently stirred by the thermal expansion and floating of the air (N2+ 0□). , MoO2, CaWO, and powder having a large specific gravity are dispersed and diffused over a wide range of molten steel due to their kinetic energy, increasing the chances of encountering reducing elements such as <St> and <C> in the molten steel. Therefore, Mob3t CaVi'l which is prone to evaporation loss:
) 4 will be promptly reduced and recovered. The reduced <MO> and <W> are uniformly diffused throughout the molten steel due to the stirring effect of the carrier gas injection, and no segregation occurs. On the other hand, <Si> and the like subjected to the reduction become 5IO2 oxides 8 and the like, which rise in the molten steel 6 and enter the slag 4.

Note that the St content in the molten steel before blowing is desirably 0.05% by weight or more in order to promote the reduction of the oxides mentioned above and to suppress evaporation loss as oxides.

The present invention will be further explained based on examples.

Example 1 When melting MO gold-containing die steel from molten steel using a 30 TON arc electric furnace, M00 from an immersion lance was used.
3 powder 403 Ky in molten steel with a mixing ratio of powder to carrier gas (air) of 33.8 weight J't%.
MO was reduced and added to the molten steel by blowing at high pressure from a lance immersed to a depth of 50 mm. The blowing conditions at this time are shown in Table 1.

Table 2g1 The blowing timing in this example is the end of the melting period in the steel melting process, and the blowing operation time is 3 minutes. Table 2 shows the results of adding Mo using the method of the present invention.The amount of MO component in molten steel was 0.39% MO at the time of melting, but 0.88% MO when the injection of M2O3 was completed.
It rose to O. On the other hand, the amount of Si component is 0605 when dissolved.
% St to 0.03% St. This shows that M2O3 undergoes a violent reduction reaction with reducing elements such as Si in the molten steel at the same time as M003 is injected. This reduction reaction formula is as follows. In other words, rsz in molten steel before M003 injection
The higher the value of 1, the faster the reaction (2) proceeds, making it possible to suppress evaporation loss in the form of M2O3. Even in the oxidation period, MO component I
is reduced and recovered to 0.91%, while rsiJ in the molten steel decreases to 0001%. This is presumably because non-reduced M003 reacts with reducing elements r Si j etc. in molten steel even in an oxidizing atmosphere.

Furthermore, in reduced JIJl, 50 thieferosilicon 7
When 00 KQ is introduced, the MO-containing stitch increases to 1.07%, and 81% becomes 0°43 stitch.

As described above, in this example, when the mixing ratio of the MoO3 powder to the carrier gas (air) was set to 33.8% by weight, it was found that the yield of MO was improved to approximately 100%.

Example 2 In making mold steel containing W from molten copper crack resistant to 1.10 inch W using a 30 TON arc electric furnace, CavJo4 powder 600 ~ was added from a lance immersed in the molten steel. The mixture ratio of CaWO and powder to carrier gas (air) was set to 46.6%, and W was reduced and added to the molten steel by blowing into the molten steel to a depth of 750 cm under high pressure.

In this example, blowing was performed immediately before the reduction period of the melting process.

show.

Since the molten steel used in this example had a low content of 0.02% 81, 50 kg of 50% ferrosilicon, 375 Kq of SiMn, and At2 Kp were added to the molten steel immediately before CaWo was blown into the molten steel. At that time, <St>chi in the molten steel rose to 0.23 t.

Then, after blowing, <W>S in the molten steel increases from o, 155w during the oxidation period to 1°11%W, while <
St > 0.06% decreased to 0.06%. Furthermore, in the reduction period, SiMn 10 oct, FSi 100K
Insert g.

Although it was added, <St>S only increased, and W> was almost the same. This can be confirmed by the method of the present invention.
)4 powder is injected deeply into molten steel together with a carrier gas (air) at a predetermined mixing ratio, reducing elements such as (St), etc. It was found that the reduction reaction was rapid and efficient reduction recovery was possible.

As is clear from the above explanation, according to the method of the present invention, Mo, which is a metal that is difficult to dissolve when added alone,
W can be added to molten steel at high yields and in a short time, and even when added as a volatile oxide, there is little evaporation loss and it can be added at high yields. It is something that can be demonstrated.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the relationship between the vaporization loss rate of MoO8 and retention time, and Fig. 2 shows the results of investigating the relationship between the mixing ratio of Mob, CaWO4 to carrier gas and the yield of Mo and W using the method of the present invention. The graph shown in FIG. 3 is a schematic diagram illustrating an example of the blowing situation according to the method of the present invention. 1...Furnace, 2...Immersion lance, 3...: Molten steel, 4...
...Slag, 6a, 6b...'dispersion zone of a mixture of powder and carrier gas. Patent Applicant: Daido Steel Co., Ltd. Representative Patent Attorney Yutaka Oshio Figure 1 Holding time (-'') Figure 2 Sanri Aihi (%)

Claims (4)

[Claims] (1) When Mo and W are added to molten steel, the Mo
, W oxide powder or granules are blown into the molten steel together with a carrier gas through a lance immersed in the molten steel. (2) The mixing ratio of powder or granules made of oxides of Mo and W to the carrier gas is 30% by weight or more50
Heavy failure - The alloy addition method according to claim (1), which is as follows. (3) Claim (1) or (2) in which the oxide of Mo is MoO2 and the oxide of W is C4.
Alloy addition method described in section. (4) The alloy addition method according to claim (1), (2) or (3), wherein the Si content in the molten steel before blowing is 0.05 weight or more.