JPH04198298A - Lubicant for hot rolling of nonferrous metallic material - Google Patents

Abstract

PURPOSE:To provide the title lubricant for preventing seizure to a rolling mill and improving the surface properties of rolled products by dispersing specific inorganic particulates in a viscous aqueous solution. CONSTITUTION:The title lubricant is prepared by dispersing 1-30wt.% of one or more inorganic particulates selected from MOS2, BN, PbO, PbS, CaF2, alumina, titania, graphite, iron oxides, NiO, Cr2O3 and inorganic silicates, wherein 90wt.% or more of the particulates have particle sizes of 10mum or less, in a viscous aqueous solution which is adjusted in viscosity to 1X10<3>-5X10<5>cP by adding a water-soluble high--molecular thickener.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is particularly applicable to metal materials such as aluminum, titanium, and nickel, or non-ferrous alloy materials containing them (hereinafter referred to as non-ferrous materials in the present specification) under high loads. The present invention relates to a hot rolling lubricant that suppresses seizing on rolling rolls when rolling metal materials (collectively referred to as metal materials) at high temperatures.

[Prior Art] When a metal material is rolled at a high temperature, when the material to be rolled is sewn onto the rolling roll, flaws are generated on the circumferential surface of the rolling roll, and these flaws are transferred to the material to be rolled, resulting in surface flaws. If such surface flaws occur, even if they are mild, the material becomes unsuitable for use in mirror finishing applications where surface texture is important. As a result, the uses of the obtained metal plate are restricted. Also,
It becomes necessary to clean the surface of a metal plate with surface flaws through a polishing process. Furthermore, if the degree of flaw is significant, the product cannot be shipped and will be scrapped. Therefore, the yield is reduced by 1, which causes an increase in manufacturing costs.

Expensive non-ferrous metal materials may not be so constrained by the increased cost of processing to improve the surface quality of the material itself. However, the occurrence of seizure in the rolling rolls also deteriorates the surface quality of other materials such as steel materials that are rolled at the same time. In this respect as well, prevention of seizure occurring in rolling rolls has become an important issue. “ Regarding surface defects caused by seizure, various methods have been considered to suppress the occurrence of surface defects, especially in the field of hot rolling of stainless steel and other steels where surface roughness is a problem. For example, it has been reported that the occurrence of surface flaws can be suppressed by reducing the load on the rolling rolls, selecting rolling conditions, selecting the roll material, and improving the lubricant, among others, grain rolls are particularly effective in preventing seizure. It is said that

[Problem to be solved by the invention] The occurrence of surface flaws has been studied in the past, especially in hot rolling of stainless steel plates, ordinary steel, special steel, etc., but it also occurs in the rolling of non-ferrous metal materials. be. for example,
As a recent trend, large rolling loads have been adopted as a means of increasing productivity and improving material quality.

Further, even under rolling conditions using multi-stage rolling stands, the rolling load of the stands near the entrance of the rolling mill is set to be large. In such a case, the oxide film formed on the surface of the nonferrous metal material that is the material to be rolled is destroyed, metal-to-metal contact occurs between the material and the rolling roll, and seizure is likely to occur.

In response to the occurrence of such seizure, various attempts have been made to prevent the occurrence of surface flaws by improving lubricants. A lubricant is present between a rolling roll and a material to be rolled and has the effect of lowering the coefficient of friction, and therefore various lubricants have been developed in the field of rolling ordinary steel. However, the current situation is that existing animal or vegetable oils, mineral or synthetic lubricating oils, etc. do not have sufficient anti-seizure effects.

Therefore, the present invention uses a substance that prevents melummetal contact between the material to be rolled and the roll and also has a lubricating effect as an alternative to these conventional lubricants. The purpose is to produce rolled products with no sticking and excellent surface quality.

[Means for Solving the Problems] In order to achieve the object, the hot rolling lubricant of the present invention contains Mo52, BN, PbO, PbS, CaF, graphite iron oxide, alumina, titania, nickel oxide,
It is characterized in that one or more types of inorganic fine particles selected from chromium oxide and inorganic silicates are dispersed in a viscous aqueous solution at a ratio of 1 to 30% by weight.

Here, it is preferable to use inorganic fine particles in which 90% by weight or more is fine powder with a particle size of 10 LLm or less. In addition, a water-soluble polymer thickener is added to the viscous aqueous solution to increase the viscosity to 1xl.
o” to 5×10′ cP.

[Function] The cause of surface flaws on non-ferrous metal materials when rolled at high temperatures is that the rolled material seizes on the rolling rolls, similar to hot rolling of steel materials, and the seizure is repeatedly transferred to the rolled material. It is in. For this reason, it is not possible to freely perform the rolling operation with respect to the type of material to be rolled, and production efficiency is suppressed. In addition, a rolling roll with seizure must be replaced with a roll having a good surface quality, which unavoidably lowers operating efficiency due to an increase in roll consumption, an increase in rolling downtime, and the like.

The present inventors have been conducting research on roll seizure during hot rolling of various steel materials including stainless steel for many years. During this time, we have experienced that roll seizure tends to occur during high-speed rolling under high pressure as slabs increase in size, and is particularly noticeable when the steel type of the rolled material is changed. This is due to the fact that when rolling under high loads, the oxide film that has formed on the surface of the rolled material is destroyed, and there is not enough time to form a scale layer that protects the newly formed surface. It turned out that it was possible.

Problems are particularly common in tandem mills with high rolling speeds, and there are fewer cases of surface defects in Stetskell mills, etc.
This shows the importance of the protective effect of scale.

Therefore, the present inventors have considered preventing seizure by replenishing the missing scale from the outside and preventing metal-to-metal contact between the material to be rolled and the rolling roll.

In this series, JP-A-64-83309 introduced the use of iron oxide powder dispersed in a viscous aqueous solution as a lubricant for hot rolling of stainless steel.
JP-A-1-167396 introduced the use of graphite powder similarly dispersed in a viscous aqueous solution as a lubricant for hot rolling of stainless steel.

When using this type of lubricant, even when using a high Cr roll as a work roll, which is particularly compatible with stainless steel, which is the material to be rolled,
Roll seizure of stainless steel can be prevented even when hot rolling is performed at high temperatures of 10 to 50 kgf/mm' while applying a high load of 10 to 50 kgf/mm'.

Subsequently, the present inventors investigated and researched substances other than iron oxide powder and graphite in order to prevent seizure by further avoiding metal-to-metal contact. The possibility of adopting the material for rolling was investigated. As a result, M o S *,
B N , P b O, P b S .

It was discovered that CaF 2 , graphite iron oxide, alumina, titania, nickel oxide, chromium oxide, inorganic silicate, etc. function as similarly effective lubricant components, leading to the present invention. Note that these inorganic fine particles may be dispersed in the viscous aqueous solution alone or in combination.

The amount of inorganic fine particles dispersed in the viscous aqueous solution must be maintained at 1 to 30% by weight. This amount of dispersion is 1% by weight.
If the amount is less than 30% by weight, the anti-seize effect due to the addition of inorganic fine particles will be small.On the other hand, in the case of a viscous aqueous solution in which inorganic fine particles are dispersed in an amount exceeding 30% by weight, the discharge energy when spraying the aqueous solution onto a rolling roll will be lower. is required to be significantly larger. This not only impairs economic efficiency, but also tends to cause problems such as graphite powder precipitating and accumulating in the conduit and clogging the conduit.

In addition, the particle size of the inorganic fine particles is preferably such that 90% by weight or more has a particle size of 10 μm or less, in order to maintain a homogeneous dispersion state in an aqueous solution.
m or less, a homogeneous dispersion state is maintained even after an aqueous solution in which inorganic fine particles are dispersed is left for one week. In addition, by reducing the particle size, a good dispersion state can be obtained even in a relatively low viscosity aqueous solution. Furthermore, by reducing the particle size, it is possible to prevent the inorganic fine particles from having a negative effect on the surface of the material.

The viscosity of the aqueous solution in which the inorganic fine particles are dispersed is increased by adding a water-soluble polymer thickener to a viscosity of 1 x 1 x 103 ~
Preferably, it is adjusted to 5x 10' cP (centipoise). When the viscosity is maintained within this range, adhesion to the mill rolls is adequate.

Among the inorganic fine particles, molybdenum disulfide M o S * is known as a solid lubricant having a layered structure that is easily sheared. When this is supplied to hot rolling rolls, metal-to-metal contact is suppressed while utilizing lubricity. As a result, an anti-seize effect is exhibited.

Boron nitride BN has a 60,000-grade layered crystal structure and is known as a substance that has a lubricating effect similar to molybdenum disulfide M o S x. Additionally, it has a high melting point of 3000°C and is a stable substance. For this purpose, boron nitride BN is
It has a great effect of suppressing metal-to-metal contact between the rolled material and the rolling roll.

Lead oxide PbO and lead sulfide Pbs have relatively low melting points (,
In the hot rolling temperature range of stainless steel, it is in a molten or semi-molten state. By covering the surface of the rolling roll with this melt, metal-to-metal contact is avoided and seizure is prevented.

Calcium fluoride, CaF, has a high melting point of 1373° C., exhibits excellent lubricity at high temperatures, prevents metal-to-metal contact, and suppresses seizure on rolling rolls.

Graphite has a layered structure in which hexagonal plate-shaped crystals are connected, and its decomposition temperature is as high as 3498°C. Therefore, even at the hot or warm rolling temperature of most rolled materials, it is sufficiently stably maintained in the initial state, and moreover, it causes sliding deformation at the pleated surface and lowers the coefficient of friction. It is also used as an effective substance that prevents metal-to-metal contact between the material to be rolled and the rolling rolls and exhibits a lubricating effect.

Iron oxide, alumina A I2* O2, titania Ti0z
.

Nickel oxide N-mil, oxidized ROM Crabs, etc. are all hard oxides that are stable at high temperatures. Note that the iron oxide may be used in the form of one type or a mixture of two or more of Fed, Few O2, Fes 04, and the like. These oxides are the aforementioned Mo5t,
Slightly inferior to BN, PbO, PbS, etc. However, it forms a stable oxide film between the rolled material and the rolling roll, preventing metal-to-metal contact between the two, and has a large effect on preventing seizure.Also, it is supplied to the surface of the rolled material as a lubricant. Since the amount is small, even if it remains on the surface of the rolled material despite being a hard oxide, there is little risk of accelerating wear of the rolling rolls. Moreover, since it is a stable oxide, it does not penetrate into the rolled material and is easily removed in the subsequent pickling process.
There is no adverse effect on pickling properties.

Inorganic silicates are composite oxides of silica and metal oxides, and typical examples include mica and glass. Many inorganic silicates become molten in the rolling atmosphere.
A film is formed as a melt on the surface of the rolling roll, avoiding direct contact with the material to be rolled.

Furthermore, the type of water-soluble polymer thickener added to adjust the viscosity of the viscous aqueous solution is not particularly limited. However, when considering the corrosivity of the lubricant when it scatters and adheres to surrounding rolling equipment, a neutral or weakly alkaline lubricant is preferable. Furthermore, it is preferable to use a thickener that exhibits stable viscosity even when the pH of the lubricant is adjusted. Examples of such thickeners include acrylic acid polymers and carboxyvinyl polymers.

[Examples] Hereinafter, the present invention will be specifically described by way of examples with reference to the drawings.

90%N of Higashitanetanuni board thickness 20mm, width 50mm, length 150mm
An i-10% Cr nickel chromium alloy was used as a material to be rolled and was rolled by one-bath rolling at a rolling temperature of 1000° C. and a rolling reduction of 50%. At this time, a roll made with a hot tool m5KD61 was used as the rolling roll. Further, the material to be rolled was heated for a short time in a furnace into which an inert gas was introduced, and the amount of scale generated on the surface of the material to be rolled was suppressed as much as possible so that the film thickness was about 1 μm.

A lubricant was sprayed onto the surface of a roll having a diameter of 350 mm and a barrel length of 300 mm during hot rolling. That is, as shown in FIG. 1, the lubricant contained in the lubricant container 1 is sent to the injection nozzle 3 via the supply conduit 2 using a pump with a pressure of 100 kgf/cm2, and from the injection nozzle 3. Fine lubricant droplets 4 were sprayed onto the circumferential surface of a rolling roll 5 rotating at 40 rpm. The injection field was 200 mm, and the injection time was set to 3 seconds.

As a result, a total weight of 5 g of lubricant was supplied to the circumferential surface of the rolling roll 5. This amount corresponds to forming a liquid film with a thickness of about 20 μm.

After injecting the lubricant onto the circumferential surface of the rolling roll 5, the water contained in the high-pressure water container 6 is pumped from the nozzle 7 at a pressure of 3
kgf/cm'' as water droplets 8. This water supply corresponds to the supply of roll cooling water of a hot rolling mill. If so, the rate of falling down will be reduced, and the rolling roll 5
This increases the adhesion rate of lubricant to

As shown in Table 1, the lubricant has an average particle size of 1.1
A viscous aqueous solution containing various inorganic fine particles having a maximum particle size of 5 μm or less and an acrylic acid polymer as a thickener was used. After rolling, the surfaces of the rolling roll 5 and the rolled material were observed to check for occurrence of seizure. The results are shown in Table 1.

As is clear from Table 1, Mo5t according to the invention,
A lubricant containing BN, pbo, pb2, CaFz, etc. exhibits a sufficient anti-seizure effect, making it possible to produce a rolled sheet with excellent surface properties. Furthermore, the lubricity during rolling was excellent, and the roll reduction blades worked efficiently on the material to be rolled, allowing rolling to be carried out without producing defects such as poor shape.

(Hereinafter, the margin of this page) Supporting evidence l: The stability of fine particle dispersion was investigated in lubricants prepared by varying the amount of inorganic fine particles such as BN and AJ2.0s dispersed in a viscous aqueous solution and the viscosity of the viscous aqueous solution. . Dispersion stability is determined by mixing the lubricant, placing it in a beaker, and letting it stand.
Judgment was made based on the state of dispersion of the fine particles after one week. As an investigation method, a lubricant sample was taken from the upper part of the beaker, the content of fine particles contained in the sample liquid was measured, and the ratio to the content at the initial stage of preparation was determined.

As for the particle size of the inorganic fine particles, as in Example 1, those having an average particle size of 1.1 μm and a maximum particle size of 5 μm or less were used. Furthermore, an acrylic acid polymer was used as a thickener for the viscous aqueous solution.

The results of the investigation on fine particle dispersibility are shown in Table 2.

(Hereinafter, the margin of this page) As is clear from Table 2, the amount of dispersion of inorganic fine particles is
As long as the viscosity of the viscous aqueous solution is maintained at ~30% by weight, and as long as the viscosity of the viscous aqueous solution is kept at I was almost the same as at the initial stage of preparation. That is, it can be seen that no sedimentation of fine particles occurred and a stable dispersion state was obtained.

This stable dispersion state indicates that the lubricant can be supplied to the rolling rolls under stable conditions for a long period of time without causing problems such as settling or clogging in the lubricant supply conduit or supply nozzle.

[Effects of the Invention] As explained above, when the lubricant of the present invention is used, a stable lubricant film is formed on the circumferential surface of the rolling roll, and the metal-metal gap between the rolling roll and the rolled material is Contact can be avoided. As a result, the rolled material is prevented from sticking to the circumferential surface of the rolling roll, and a metal plate without defects such as surface flaws can be obtained. Due to its excellent surface properties, this metal plate can be used in a wide range of fields without being subject to any restrictions. Also,
Since the work load of surface care in the subsequent process is also eased, manufacturing costs can also be reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a mechanism for spraying lubricant onto rolling rolls. 1: Lubricant container 2: Supply conduit 3: Spray nozzle 4: Lubricant droplet 5: Rolling roll 6: High pressure water container 7: Cooling water nozzle 8: Water droplet

Claims (3)

[Claims] (1) MoS_2, BN, PbO, PbS, CaF_2
, alumina, titania, graphite, iron oxide, nickel oxide, chromium oxide, and inorganic silicate, one or more types of inorganic fine particles are dispersed in a viscous aqueous solution at a ratio of 1 to 30% by weight. A lubricant for hot rolling of non-ferrous metal materials. (2) A lubricant for hot rolling of nonferrous metal materials, wherein 90% by weight or more of the inorganic fine particles according to claim 1 are fine powders having a particle size of 10 μm or less. (3) Hot rolling of a nonferrous metal material, characterized in that a water-soluble polymer thickener is added to the viscous aqueous solution according to claim 1, and the viscosity is adjusted to 1 x 10^3 to 5 x 10^5 cP. lubricant for use.