JPS5841940B2 - Solid heat-generating heat insulating agent for boiler - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid heat-generating heat-insulating material formed by molding a powdery heat-insulating agent and heat-generating agent into a cylindrical body, which is used in a feeder for casting steel castings.

The riser attached to the casting has the role of preventing the occurrence of casting defects such as cavities by replenishing molten metal in response to the shrinkage of the casting body as it solidifies. must be maintained in a molten state with sufficient fluidity until

For this reason, as a means of preventing and suppressing heat conduction and heat dissipation, a heat-insulating or heat-generating sleeve is usually provided in the feeder part, and a heat-insulating layer is formed by spraying a powdered heat insulating agent on the feeder surface. This is done to prevent heat dissipation, or a powdered exothermic agent is sprayed to supply heat and prevent heat dissipation.

However, its heat insulation and heat retention effects are not necessarily sufficient, and as shown in Fig. 1, the feeder 1 after solidification has a V
Deep, character-shaped withdrawal cavities 2 are generated, and a segregation zone in which carbon and other molten metal alloy elements are concentrated is generally present directly below the withdrawal cavities.

If such cavities or segregation reach the casting body, it will become a fatal defect in the cast product, so as a preventive measure, it is necessary to
A method has been adopted in which the height H of the riser is increased so that even if it occurs, it does not reach the main body.

In other words, the normal feeder height H is approximately 0 relative to the feeder diameter.
．． It is designed to have a ratio of 8D to 1.0D.

For this reason, the ratio of the feeder amount to the total amount of poured metal excluding the runner area [feeder amount/) (casting body weight + feeder amount) x 100 (
%)] reaches about 30 to 50%, and for example, to obtain a casting body of 500 kg, a large amount of feeder weighing about 200 to 500 kg is required.

Therefore, in order to supply such a large amount of feeder, a large amount of molten metal must be produced in a melting furnace such as an electric furnace, which requires a correspondingly large amount of energy.

If the feeder can be solidified into a flat shape as shown in Figure 2 without causing any cavities, the feeder height H
can be lowered, and the amount of molten metal required will decrease accordingly.
This makes it possible to save energy.

Based on the above viewpoint, the present inventors previously applied for a patent entitled "Method for manufacturing steel castings" (Japanese Patent Application No. 55-98460).
provides a method of keeping the feeder warm by using a heat insulating agent and a heat generating agent in combination, thereby making it possible to solidify the feeder into a horizontal state with no voids in the V-shaped rows as shown in FIG. 2. As a result, the required feeder height H was reduced to approximately 0.5 D or less, and the energy required for melting the molten metal was successfully reduced significantly.

By the way, heat insulators and exothermic agents are in powder form, and when spraying them on the feeder surface, a bag filled with the required amount is poured onto the feeder surface at an appropriate time after pouring the hot water. This is done by

However, when there are many feeders for castings in one charge, it takes a lot of effort to put one bag into each one.Especially in the above method, the exothermic agent is first sprayed, and then The amount of work will double as heat insulators will be sprayed.

In this case, it is not preferable to mix the exothermic agent and the heat insulating agent and spray them all at once, as the effects of each will be diminished.

In addition, since exothermic agents and heat insulating agents are in powder form, when they are sprayed, the exothermic reaction on the feeder surface and the strong hot air from the surface of the hot water cause them to boil over, resulting in a considerable amount of waste, which increases the unit cost. I have to accept it.

The solid heat-generating heat insulating agent for a feeder of the present invention is used for a feeder in casting steel using a sand mold, has one or more through holes in the vertical direction, and has a thermite-based heat-generating agent. It is a cylindrical press-molded body having a two-layer structure including a lower layer made of alumina-based heat insulating agent and an upper layer made of an alumina-based heat insulating agent.

The exothermic agent in the lower layer supplies heat to the feeder through its own strong exothermic and combustion reaction, and turns into slag after combustion to form a heat insulating layer, while the heat insulating agent in the upper layer either does not generate exothermic or combustion reaction or even if it does. It has a low calorific value, and has a heat insulating effect that blocks radiation and heat dissipation from the feeder surface.

The solid exothermic heat insulating agent according to the present invention is as shown in FIG.
Solidified lower heat generating agent layer 3 and upper heat retaining agent layer 4 2
A cylindrical molding having one or more holes 5 that open at the upper end surface of the heat-retaining agent layer 4 and extend vertically almost parallel to the axial direction so as to reach the lower proinflammatory agent layer 4. By placing this on the top of the feeder after pouring, it is possible to eliminate the duplication of the above-mentioned spraying work, prevent loss when pouring over the top of the feeder, and as described below. This improves the work environment by shortening the worker's restraint time and reducing the amount of dust and smoke generated.Moreover, the feeder can be solidified into a perfect V-shaped shape with no cavities as shown in Figure 2 above. can.

The holes 5 provided in the cylindrical molded body are the heat generating agent layer 3 and the heat insulating agent layer 4.
Therefore, the shape, size, number, etc. of the holes can be arbitrary as long as the holes communicate each layer with the atmosphere and can supply enough oxygen. It may be.

Normally, from the viewpoint of molding workability, etc., it is sufficient to form through-holes that open at the top and both end faces of the cylindrical body, and are distributed almost evenly across the cross section of the cylindrical body.

The solid heat generating heat insulating agent according to the present invention is produced by adding a binder to each of the powdered heat generating agent and heat retaining agent, mixing them uniformly to form a mixed material, and placing each mixed material in a hollow cylindrical molding machine. Top/Bottom 2
It is manufactured by filling a layer and compression molding it by applying a certain pressing force in the axial direction, and then drying the obtained molded product.

Alternatively, the holes 5 may be formed by embedding a rod-shaped body when filling the kneaded material into the molding machine and removing it after pressure molding.
Alternatively, it may be formed using a suitable perforation means after pressure molding.

However, the solid exothermic heat insulating agent of the present invention can be produced using the procedures and molding means used in the production of so-called briquettes.

Various commercially available powder agents may be used as the exothermic agent and heat insulating agent constituting the solid exothermic heat insulating agent of the present invention.

The exothermic agent is generally a thermite type mainly composed of aluminum powder and iron oxide, for example, Fe050-70%.
(% by weight, the same applies hereinafter), A115 to 25%, and other materials containing 15% or less of Ca-8i and 210% or less of CaF are preferably used.

On the other hand, the heat insulating agent is Al20335-55%, Al25-55%
It is an alumina-based heat insulating agent containing 40% FeO3 to 15%, 5iO2 10% or less, and an expandable one containing 5% or less graphite oxide as an expanding agent is preferably used.

This swelling agent has the effect of swelling the heat insulating agent and exothermic agent after they have been turned into slag, thereby increasing their heat insulating effect.

The binder to be added to the heat generating agent and heat retaining agent is as follows:
Various materials are used that have a caking effect that allows easy molding into a predetermined cylindrical body and provides shape retention that makes it difficult to remove the shell during handling.

Examples of inorganic binders include clay and bentonite, and examples of organic binders include starch-based binders such as molasses and dextrin, and synthetic resin-based binders such as vinyl acetate resin emulsion.

Of course, desirable properties that a binder should have include, in addition to the necessary caking effect, ease of mixing with powder, rapid drying after molding, and the ability to interfere with the original functions of heat-generating agents and heat-insulating agents. In addition, in the case of organic binders, no harmful gases are generated when placed in the feeder.

Furthermore, after the heat generating agent layer and the heat insulating layer turn into slag on the feeder surface, they function as a heat insulating layer to prevent heat dissipation from the feeder surface, so they easily disintegrate and cover the feeder surface. It is necessary to.

Typical examples of preferred binders satisfying these conditions include dextrin and synthetic resin emulsions.

In particular, dextrin exhibits a good caking effect when used in small amounts, it decomposes itself thermally and acts as a combustion improver, and after thermal decomposition, it makes the exothermic layer etc. porous to facilitate the supply of oxygen. It is one of the most suitable binders with excellent functions such as rapidly disintegrating the heat generating agent layer and the heat retaining agent layer, swelling them, and enhancing the heat insulating effect.

The required amount of the binder to be added varies depending on the degree of the binder itself, the particle size (powder particle surface area) of the heat insulating agent and exothermic agent, etc., but it is necessary to ensure that the resulting cylindrical molded product has shape retention that can withstand handling. It should be adjusted as appropriate within a range that does not inhibit the original functions of the heat insulating agent and exothermic agent.

To give a specific example, when using dextrin, it should be about 1 to 7% by weight relative to the exothermic agent or heat insulating agent.
Preferably 2 to 6%, for synthetic resin emulsions such as vinyl acetate resin, about 2 to 10%, preferably 4 to 8%.
%.

However, the exothermic agent is generally made of coarse powder such as Al powder, while the heat insulating agent is generally made of fine powder.
For the former, the amount added may be relatively small within the above range, but for the latter, it is better to adjust the amount to a slightly winter level.

If too much clay, bentonite, etc. is added, it will inhibit the function of the heat insulator and exothermic agent, so when using clay, the upper limit should be about 10%, and for bentonite, the upper limit should be about 8%, but the amount added within this range. If the caking effect is insufficient, it is advisable to use a means for reinforcing the shape retention of the molded article as described later.

It is also possible to use a combination of two binders, for example dextrin and bentonite.

In addition, when adding a binder and preparing a kneaded product, an appropriate amount of water is added to appropriately dilute the binder and promote uniform dispersion and infiltration between powder particles.

The amount of water added may be the minimum amount necessary to promote dispersion and infiltration of the binder between powder particles; if it is too large, it will take a long time to dry the press-molded product.

Although the amount depends on the type of binder, it may generally be adjusted within a range of about 3 to 15% by weight based on the entire kneaded material.

The mixed materials of the heat insulating agent and the exothermic agent are then filled into a hollow cylindrical molding device having a predetermined shape in two layers, upper and lower, and pressed in the axial direction to mold.

For this pressure forming, a pressure forming apparatus used for manufacturing so-called smoked charcoal can be used.

Of course, the cross-sectional shape of the cylindrical molded body must correspond to the cross-sectional shape of the feeder used.

Generally, it is formed into a cylindrical body with a circular cross section.

The pressure applied during molding affects the rough density of the resulting molded product.

If the pressurizing force is too small, shape retention is poor and it is easy to break during handling, while if it is too large, the combustion reaction when applied to the feeder is undesirably delayed.

From this point of view, the apparent density of the molded product is usually about 15 to 2.
0? It is preferable that the molding be performed by applying a pressure such that the pressure is about /cni.

Further, the holes 5 may be formed simultaneously with the pressure molding as described above, or after the pressure molding.

The diameter of the pores may be approximately 5 to 20 mm, and the number may be increased or decreased appropriately depending on the cross-sectional area of the molded body, but for example, in a molded body with a diameter of 13 CrrL, it is sufficient to disperse approximately 4 to 6 pores. It is.

In addition, if the molded product uses a binder with relatively low binding strength, such as clay or bentonite, its shape retention will be somewhat insufficient, and it may be damaged during handling when removed from the molding machine. It may be accompanied.

In such a case, as a reinforcing means, for example,
It is preferable to embed a stick-like piece of wood as a splint 7 in the molded body 6, as shown in FIG.

The former can be filled in when filling the kneaded material into the molding machine.
Also, the latter should be fitted in advance along the inner circumferential surface of the molding machine (・.

The molded article obtained above is then dried to remove moisture.

The drying may be done by natural drying or by heating.

Of course, when using an organic binder such as dextrin, thermal decomposition due to heating must not occur.

Usually, the heating temperature is around 100°C or lower.

When the thus obtained solid exothermic heat insulating agent of the present invention is placed on the feeder surface, the exothermic agent layer in contact with the hot water surface first burns, supplies heat to the feeder, collapses itself and turns into slag, and further disintegrates into the upper part. The heat insulating layer also collapses and becomes a swollen heat insulating layer that covers the feeder surface, effectively blocking heat dissipation from the feeder surface, and as shown in Figure 2 above, the formation of cavities. Solidify into a single-story shape.

The required amount of exothermic agent and heat insulating agent to be administered onto the surface of the feeder varies depending on the surface area of the feeder, but the amount of exothermic agent applied per unit area of the feeder is approximately 5 to 10? 10tt, about 2-5 insulators? /
cni is suitable.

Of course, this amount can be determined by adjusting the amount filled into the molding machine during the pressure molding.

In addition, for the riser, a normally used sleeve, for example, a so-called insulating sleeve made of glass fiber solidified with an inorganic binder, or a lining made of a mixture of AI and Fed@ in a thermite reaction ratio. It is preferable to provide a so-called heat-insulating sleeve or the like.

The method for administering the solid exothermic heat insulating agent of the present invention to the feeder surface does not require any special conditions, and can be done in accordance with a conventional method, for example, immediately after pouring the hot water, using rice husks, straw, or a commercially available heat insulating powder (this powder can be used as The same type of raw material powder heat insulating agent that constitutes the solid heat generating heat insulating agent of the present invention is generally used) is sprinkled, and after a certain waiting time has elapsed, it is scraped out and the solid heat generating solid heat retaining agent of the present invention is administered. do it.

In this case, the present invention can shorten the waiting time as compared to the conventional method.

This waiting time affects the shape of the feeder after solidification, so strict management is required. It goes without saying that it depends on the weight of the main unit and the diameter, and the larger the diameter, the longer the waiting time.

The conventional waiting time using a powder exothermic agent is curve 1 in Figure 5.
For example, in the case of a feeder diameter of 30 crILΦ, it takes about 60 minutes.

However, when the solid exothermic heat insulating agent of the present invention is used, as shown by curve 11 in the same figure, the time to add the heat insulating agent can be greatly advanced, and in a feeder with a diameter of 30 cIrLΦ, the waiting time is only 30 minutes. Also, when the diameter is about 16 cynΦ or less, it can be administered immediately after pouring the water without waiting.

Of course, when administering immediately after pouring hot water, there is no need to sprinkle rice husks or the like, and it is sufficient to administer directly onto the feeder surface.

The reason why the waiting time can be shortened in this way is that when conventionally administered as a powder, the reaction is completed quickly, but when administered in solid form, the reaction is suppressed more quickly. This is thought to be due to the continuous combustion.

As mentioned above, when the solid exothermic heat insulating agent of the present invention is used, the waiting time is shortened. This will speed up the movement of the mold after administration (for example, transporting it from the pouring workshop to the mold cutting workshop).
It is possible to improve casting work efficiency.

The steel types to which the solid exothermic heat insulating agent of the present invention is applicable include various SC carbon steels, SCMn, and SCCrM.

Any material may be used, such as structural high-strength carbon steel or low-alloy cast steel such as SCMnCrM, various high-temperature and high-pressure cast steels such as 5CPH, various stainless steel cast steels SC8, and heat-resistant cast steels such as SCH.

Next, examples of the present invention will be described.

Examples Mixed mixtures of exothermic agents and heat insulators having various compositions shown in Table 1 were prepared, pressure molded and dried to produce solid heat generating heat insulating agents having cylindrical shapes shown in Tables 1 and 2. For sizes, see the right column of the same table).

Each molded body has a through hole (approximately 5 to 20 mm in diameter) approximately parallel to the axis.
im) have 3 to 5 pieces.

As the exothermic agent, the product name "U-melt J" (manufactured by Kamogawa Kogyo Co., Ltd., thermite type) or "Calmex" is used.
(manufactured by Fuoseco Japan Limited, thermite type)
As the heat insulating agent, the product name "UT-35 Kai" (manufactured by Kamogawa Kogyo Co., Ltd.) or "Felax" (manufactured by Fuoseco Japan Limited) was used.

Its chemical composition is approximately as follows.

'[J-melt and Calmex Fe060-7
0%, Al2O~25%, UT-35 modified and Ferrax A120343~48%, Al30~35%, F
e06-10%, CaO4-8%.

In the table, "Bond" in the "Binder" column is a vinyl acetate resin emulsion commercially available under the trade name "Woodworking Adhesive Bond" (manufactured by Konishi Co., Ltd.).

After each solid exothermic heat insulating agent was pressure-molded, it was dried in a heavy oil continuous furnace at a heating temperature of 95° C.±5° C. and a holding time of 60 minutes and 10 minutes.

Using each of the above-mentioned solid exothermic heat insulating agents, a cast body (wheel) shown in FIG. 7 was cast using a sand mold under the following general casting conditions.

(i) Cast steel: JISG511 lSNCMn2A
(C0, 25-0.35%, SiO, 3-0.6%,
Mn1.0-1.6%, P<0.04%, S<0.04
%).

(+*) Casting temperature: 1570℃±10℃)
Mold material: DICAL mold (inorganic self-hardening mold) containing 91% silica sand, 7% sodium silicate, and 2% DICAL powder (all by weight).

(IV) Cast body (main body) unit weight: 33-98 kg
Main body dimensions: D1100~150mmΦ, D2130~
215rnmΦ, D 250~395mmΦ, W11
00~12511Lr/L,,W2180~2201n
7IL1T15~251n11Lo feeder part dimensions: D10
0~150mm Φ, H100~150mm.

The shape retention properties of each solid exothermic heat insulating agent tested, the reaction situation when applied to the feeder surface, and the shape of the feeder after solidification are as follows.

However, a heat insulating sleeve (trade name: Luminex, manufactured by Fooseco Japari Limited) was used in the feeder section.

Furthermore, the waiting time for administration was according to the curve 11 in FIG. 5, depending on the diameter of the riser.

(N Shape retention test materials 116.1 (binder: clay) and 2 (binder: bentonite) have somewhat low shape retention after drying, but when molded, the cardboard cylindrical outer shell (thickness of approx. 1 mm), it is possible to prevent damage during handling.

The sample materials/f6.3 to 10 are quickly dried after molding and have good shape retention without being easily damaged.

(B) Reaction status and feeder shape Each sample material showed a good reaction status and collapsed after combustion, covering the feeder surface as a heat insulating layer.

In particular, sample charcoals 3 to 1o using dextrin or the like as a binder are easily turned into slag and form a swellable heat insulating layer to cover the riser.

Figure 6 shows the cross-sectional shape of the riser after solidification.

In both cases, there is no V-shaped ridge as in the conventional case, and an excellent solidified shape is exhibited.

Especially when &3 to 10 are used, the top surface of the feeder is almost completely horizontal.

As described above, in the solid exothermic heat insulating agent of the present invention, since the exothermic agent and the heat insulating agent are integrally solidified, the time and effort required for administering the heat to the feeder is reduced, and as mentioned above, the time required to administer the heat retaining agent after pouring the hot water is reduced. Since the waiting time for casting can be reduced compared to the conventional method, casting efficiency can also be increased by reducing the time required for workers to be tied up.

Furthermore, since it is a solid, there is no loss when administering it, unlike powdered medicines, which spill over to the outside, so the amount used can be reduced accordingly, and less dust is generated, which improves the working environment. You can also get

Of course, the feeder has an excellent heat-retaining and heat-insulating effect, and as shown in the above embodiment, it can be solidified into a shape without cavities, so it is possible to significantly reduce the amount of the feeder.

The weight reduction effect is due to the yield of the casting body [casting body weight/(
This results in an improvement of about 10 to 15% in terms of the casting body weight + riser amount), and greatly contributes to reducing melting costs in electric furnaces and the like.

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional explanatory views showing the solidified shape of the feeder, Figure 3 is a perspective view showing a specific example of the solid heat-generating heat insulating agent of the present invention, and Figures 4 and 5 are explanatory cross-sectional views showing the solidified shape of the feeder. Figure 5 is a graph showing the waiting time after pouring hot water until administration of exothermic agent, etc. Figures I-X are graphs showing the results obtained using the solid exothermic heat insulating agent of the present invention. FIG. 7 is an explanatory cross-sectional view showing the solidified shape of the riser, FIG. 1...Riser, 3...Heat retaining layer, 4...
... Heat generating agent layer, 5 ... Hole, 9 ...
Cast weight body, 10... sprue.

Claims (1)

[Claims] 1 A solid exothermic heat insulating agent for a riser used in casting steel using a sand mold, with an apparent density of 1.5 to 2.0?10
A, having one or more through holes in the vertical direction,
and a lower layer consisting of a thermite exothermic agent containing Fe050 to 70% by weight and A115 to 25% by weight, and Al20
335-55% by weight, Al25-40% by weight, Fe03
15% by weight or less, 10% by weight or less of 5iO2, and 5% by weight or less of graphite oxide. Heat insulating agent.