JPS58100935A - Warmth keeping method for heated metal - Google Patents

Abstract

PURPOSE:To keep warmth of a metallic material effectively without restriction of dimension and shape and without hindering the working by sticking a mixture of silicate of alkali metal, oxide or hydroxide of polyvalent metal and water on the surface of a metallic material heated for hot working. CONSTITUTION:A mixture consisting of, by weight, 10-75% silicate of alkali metal, 5-70% powder of oxide, hydroxide or carbonate of polyvalent metal, 20-80% water is stuck on the surface of a heated metallic material. This mixture is heated by heat of the metallic material and converted to porous hardened body to form a heat insulating coating on the surface of the metallic material. Accordingly, warmth keeping of the metallic material can be effected. This coating becomes flat on the material by compression during hot working. However, it works as a heat insulator though the heat insulating capacity is lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of keeping a metal material heated for hot working.

During hot working of steel and other metal materials, the workpiece cools down due to natural heat dissipation during processing, increasing deformation stress and gradually making machining difficult. Perform heating. Since the loss of thermal energy during such repeated heating and processing is enormous,
Needless to say, it is desirable from the point of view of energy saving to minimize the amount of heat dissipated during machining so that a large machining bolt can be obtained with one heating operation. In addition, in the case of austenitic steel, if the number of repeated heating increases, the crystal grains will become coarser and the quality will deteriorate, so it is important to reduce the number of repeated heating as much as possible by suppressing heat radiation during processing to ensure quality. is also necessary. Furthermore, when the cooling rate is fast, the temperature of the corners of the workpiece decreases faster than other parts, and therefore the ductility decreases more quickly, making defects such as cracks and flaws more likely to occur during processing.

Therefore, a heat insulating cover is installed as part of the equipment that performs hot processing, or a heat insulating cover is attached directly to the workpiece (Unexamined Japanese Patent Publication No. 5
Although measures such as 5-95745) have been used to suppress heat radiation during processing, the heat retention effect of the heat insulating cover on the equipment is minimal, and it is difficult to attach a heat insulating cover to the workpiece. This method has the disadvantage that it not only requires the preparation of a number of heat-insulating covers depending on the shape of the workpiece, but also obstructs the processing.

The present invention provides an extremely effective heat retention method without the above-mentioned drawbacks, that is, alkali metal silicates lO ~ 75% (weight f%, hereinafter the same), polyvalent metal oxides, hydroxides, silicates or A mixture consisting of 5-70% carbonate powder and 20-80% water is deposited on the surface of the heated metal material,
The present invention provides a heat retention method which is characterized by forming a heat insulating coating on the surface of the metal material by heating it with the heat of the metal material and converting it into a porous hardened body.

The heat retention method according to the present invention is based on a completely different concept from the above-mentioned known methods in that it forms a heat-insulating coating that is directly adhered to the metal material that is about to be processed by heating. The method of forming the heat insulating coating is also unique and unprecedented in other technical fields.

Hereinafter, the heat retention method according to the present invention will be explained in detail.

As the alkali metal silicate, which is one of the materials for forming a heat-insulating coating, sodium silicate, potassium silicate, and lithium silicate are used, but some or all of them may include SiO□/Li,
When using lithium silicate with a molar ratio of 3.0 to 8.0, a particularly heat-resistant coating is formed.

Specific examples of polyvalent metal oxide, hydroxide, silicate or carbonate powders used with alkali metal silicates include zinc, magnesium, aluminum, helium,
Contains one or more of oxides, hydroxides, silicates, or carbonates of titanium, barium, calcium, tin, copper, cadmium, nickel, lead, iron, zirconium, etc., or contains one or more of these as a main component. Examples include ore powder. Among these, particularly preferred materials are powders of aluminum oxide, aluminum hydroxide, calcium silicate, zinc oxide, titanium oxide, silica stone, mullite, kaolin, bentonite, wollastonite, talc, limestone, dolomite, and the like. The particle size of the powder is 01-1
It is desirable that the thickness be about 0μ.

These powder materials are materials that react with the alkali metal silicate heated on the metal material.H Gourd coating forming materials include inorganic materials that expand when heated, such as pearlite, vermicellite, shirasu, and expandable graphite. Non-reactive auxiliary materials such as potash titanate whiskers, fibrous reinforcing materials such as finely divided ceramic fibers, and pigments for coloring may be added as necessary.

The above materials are uniformly mixed with water at the above ratio (the alkali metal silicate is dissolved in water), and then sprayed, immersed, or roll coated onto the surface of the metal material heated for hot working.
When deposited with a uniform thickness of about 1 to 3 cages by the method described in 1., the reactive material heated by the high-temperature metal material immediately starts to react (at this time, some of the water is also removed). (It seems to be involved in the reaction.) In parallel with this, the water evaporates and, if an auxiliary material such as perlite, which expands when heated, is included, expansion occurs. As these changes progress simultaneously, on metal materials,
A coating layer that changes into a porous cured body is formed via a highly viscous foam.

The above-mentioned blending ratio of the coating forming material is necessary in order to smoothly form a porous cured body as described above, and to form a strong cured body that is sufficiently porous and adheres well to the metal material. However, since the optimum blending ratio varies depending on the type of materials used, it is desirable to determine it through experiments.

Once formed on a metal material, the porous coating layer does not shrink or peel off due to deterioration of physical properties over time or even if there is a slight temperature change. Exhibits excellent thermal insulation properties during processing.

The heat-insulating coating formed by the method of the present invention is compressed and flattened on the metal material during hot working, but
Even if the insulation performance decreases, it will continue to play a role in retaining heat.
It is possible to prevent the temperature of the copper phase from decreasing not only before hot working but also during working.

The heat retention method according to the present invention has the above-mentioned features as well as:
No restrictions due to the size or shape of metal materials.
■It forms a coating layer that adheres to the metal material, so it has a very remarkable heat retention effect.■It does not interfere with hot processing after treatment, and there is no need to modify existing processing equipment. Therefore, it is extremely effective in saving energy, reducing the number of steps, shortening the processing time, and improving the quality of hot-processed products in hot processing of metal materials.

Next, the present invention will be explained with reference to Examples.

Example 1 Carbon steel of 800φ
/I)i20=4.5) 35%, mullite fine powder (
A mixture of 20% (average particle size 1.5 μ), 1% zinc oxide, and 44 g of water was sprayed with a spray gun at approximately a kg/m2.
I sprayed it. The sprayed mixture foamed and hardened after 1 minute to form a porous coating layer about 11 strips thick.

After this treatment, the steel material temperature (temperature inside 20*x from the surface) was 990°C when it was left to cool for 1 hour.

On the other hand, the temperature of the steel material that was allowed to cool under the same conditions without being subjected to the heat insulation treatment was 790°C.

Immediately after the thermal insulation treatment, a heat insulation-treated sample other than the above-mentioned sample that had been left to cool was pressed down with a press for 50 degrees, but the coating only became flat and did not peel off, and it was possible to continue processing in the heat insulation state.

Example 2 Susao4 ring (2500φX1500φX180
0L) was heated to 1100°C in a heating furnace, taken out from the furnace, and immediately mixed with 20% sodium silicate (8i0□/Na2O molar ratio -30) and lithium silicate (S i O,/Li
2O molar ratio -s, o) 1o%, silica powder (average particle size l
.

A mixture of 1 titanium oxide and 39% water was coated with a roll coater using a roll coater. After this treatment, the temperature of the steel material (temperature inside 20 degrees from the surface) was 935 when left to cool for 1 hour.
It was ℃.

On the other hand, the temperature of the steel material that was allowed to cool under the same conditions without being subjected to the above-mentioned heat insulation treatment was 720°C.

Immediately after the heat-insulating treatment, the raw material after the heat-insulating treatment, which was different from the above-mentioned sample that had been left to cool, was expanded with a press, but the coating was on the pressed surface,
There was no peeling on either side, and it was possible to continue processing while keeping it warm.

Agent Patent Attorney Itai - Oboro

Claims (2)

[Claims] (1) A mixture consisting of 10-75% by weight of alkali metal silicate, 5-70% by weight of polyvalent metal oxide, hydroxide, silicate or carbonate powder, and 20-80% by weight of water was heated. A heated metal characterized by forming a heat insulating coating on the surface of a metal material by attaching it to the surface of the metal material and heating it with the heat of the metal material to convert it into a porous hardened body. How to keep materials warm. (2) Part or all of the alkali metal silicate is 540
2. The method according to claim 1, wherein the lithium silicate has a 2/Li□0 molar ratio of 3.0 to 80.