JP2581881B2 - Lubricant for preventing roughening of wear-resistant cast iron rolling roll and hot rolling method using the lubricant - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to hot rolling of steel,
The present invention relates to a lubricant and a hot rolling method developed for the purpose of preventing surface roughness of a roll surface when a wear-resistant cast iron roll is used.

[0002]

2. Description of the Related Art Conventionally, three types of rolls of high chrome cast iron, adamite cast iron and Ni grain cast iron have been mainly used for hot rolling of steel. However, these rolls had insufficient abrasion resistance and rough surface resistance under the severe conditions of hot rolling of steel. In recent years, Japanese Unexamined Patent Publication No. 58-87249 has improved wear resistance dramatically compared to conventional rolls.
A roll made of abrasion-resistant cast iron as disclosed in Japanese Patent Application Laid-Open Publication No. H10-210, has been developed and is being replaced with the above three types of rolls.

A roll of wear-resistant cast iron as disclosed in Japanese Patent Application Laid-Open No. 58-87249 has a surface scale of the rolled material on the roll surface during hot rolling of steel, similarly to a conventional roll. Fe ₂ O ₃ and Fe spread and called black scale
A surface oxide mainly composed of ₃ O ₄ is generated. Although the wear resistance of the wear-resistant cast iron roll is improved with respect to wear, the generation of surface oxides is not different from that of the conventional roll. As the rolling progresses, a phenomenon occurs in which the surface oxide is separated. The portion where the surface oxide has peeled off has a step difference with the portion where the oxide film has remained, resulting in roll surface roughness. The rough surface pattern of the roll is transferred to the rolled material and reduces the surface quality. Therefore, it is necessary to replace or grind the rolls, and the effect of the original wear-resistant cast iron rolls is significantly reduced.

As means for solving the above problems, a lubricant is supplied between the roll and the rolled material to lubricate between the roll and the rolled material. Lubricants include solid lubricants such as graphite water glass, boron nitride and mica, which have lubricating effects at high temperatures, extreme pressure additives such as sulfurized oils and fats, zinc dialkyldithiophosphate, phosphate esters, mineral oils, synthetic oils, oils and fats Liquid lubricants in which two or more types of oiliness improvers such as synthetic fatty acid esters are combined are generally used. Further, such a liquid lubricant is generally supplied to the roll surface by a water injection type oil supply system. Water injection type refueling equipment means tribology basics and applications.
The equipment is as described on the page (published by Kosho Publishing on September 30, 1976).

[0005]

The use of a conventional lubricant reduces the coefficient of friction by forming a lubricating film between a roll of abrasion-resistant cast iron and a rolled material, thereby reducing the surface oxidation formed on the roll surface. The main focus has been on suppressing delamination. However, in actuality, the roll surface oxide has a completely different composition from the roll base, so there is a problem that there is a difference in the internal stress and the coefficient of thermal expansion, the adhesion to the base is weak, and the friction coefficient is reduced. It was difficult to completely prevent the peeling from the roll surface by just using it.

[0006] When the oxide film formed on the roll surface is peeled off, the roll surface becomes rough due to a step difference from the portion where the oxide film remains. As a countermeasure, when the oxide film peels off from the roll surface, the rolling roll is promptly replaced with a polished roll.
However, the work of exchanging the rolls is a problem because it requires a long suspension of the rolling work and greatly reduces the work efficiency.

[0007]

In order to solve the above problems, the present inventors considered that it would be desirable to develop a lubricant capable of suppressing the formation of an oxide film on the surface of a wear-resistant cast iron roll. The reason for this is that conventionally used rolls of high chromium cast iron, adamite cast iron and Ni grain cast iron have a surface oxide formed at the time of rolling, which is more excellent in wear resistance than a base material, so that an oxide film is actively formed on the roll surface. Formation contributed to the improvement of the abrasion resistance of the roll. On the other hand, a roll of abrasion-resistant cast iron does not require the abrasion resistance of the oxide film because the base itself has excellent abrasion resistance. Rather, it is considered that it is desirable not to form an oxide film because there is no occurrence of peeling.

The lubricant of the present invention comprises a highly basic alkaline earth metal sulfonate such as a highly basic calcium sulfonate, a highly basic magnesium sulfonate, a highly basic barium sulfonate alone or a highly basic alkaline earth metal sulfonate and a mineral oil. And one or two of the esters, or one or two of the highly basic alkaline earth metals and / or mineral oils and the esters, and spherical silica particles. By applying during rolling to the surface of the wear-resistant cast iron roll, the roll surface Fe ₂ O ₃ and Fe
_This makes it possible to suppress the formation of an oxide film containing ₃ O ₄ as a main component.

[0009]

The structure and operation of the present invention will be described. The lubricant of the present invention contains a highly basic alkaline earth metal sulfonate (excluding 20 to 70% by weight). Further, the lubricant of the present invention comprises a highly basic alkaline earth metal sulfonate 10
-90% by weight (excluding 20-70% by weight) and 10 or 90% by weight (excluding 30-80% by weight) of one or two of mineral oils and esters. The high base alkaline earth metal sulfonate used in the present invention may be a known substance. To explain by taking as an example a highly basic calcium sulfonate as the highly basic alkaline earth metal, for example, after adding an excessive amount of calcium hydroxide and an aryl or alkyl sulfonic acid in a predetermined solvent, carbon dioxide gas under predetermined conditions After that, those produced by removing the solvent are preferred. The reason for this is that the overbased calcium sulfonate produced by this method is a transparent liquid in which CaCO ₃ is stably dispersed and is arbitrarily dissolved in mineral oil or ester. This is because it is possible to form a stable liquid lubricant that can be lubricated by a water injection type lubrication facility that has been generally used.

[0010] The overbased calcium sulfonate produced by the above method contains CaCO ₃ in the component. This Ca
After the CO ₃ adheres to the rolling rolls, it comes into contact with the rolled material, becomes hot, and decomposes into CaO.

Alkaline earth metal oxides such as CaO are:
Reacts with scale existing on the rolled material surface,
Into a scale mainly composed of a solid solution of CaO and FeO
It has the function of doing. This solid solution of CaO and FeO is the main component
Of the rolled material surface during hot rolling of general steel
Is different from the scale mainly composed of a solid solution of FeO
And does not spread on the roll surface, preventing the formation of oxide films.
Can be controlled. This effect is due to the
CaCO contained in um sulfonate_ThreeAccording to the work of
available. In this case, the overbased calcium sulfonate
Is CaCO in it _ThreeIs stable and colloidally dispersed.
Because it is a clear and stable liquid substance, CaCO_ThreeDifferent from powder
Fine CaCO_ThreeAdheres uniformly on the roll surface,
The spread of scale on the scale
Can be.

It is preferred that the high basic calcium sulfonate be contained in the lubricant in an amount of 10% by weight or more. It is considered that the reason for this is that when the content is 10% by weight or more, the content of CaCO ₃ is large and sufficient for forming a solid solution of CaO and FeO. On the other hand, the highly basic calcium sulfonate
If the content is less than 0% by weight, the required effect cannot be obtained because the CaCO ₃ content is small and the solid solution of CaO and FeO is insufficiently formed.

[0013] In the overbased calcium sulfonate Ca
It is preferable that CO ₃ has at least a base number of 100 or more. It is considered that the reason for this is that if CaCO ₃ is not present in the lubricant at a certain concentration or more, it is difficult to form a solid solution with FeO after CaCO ₃ is transformed into CaO.

Although the lubricant of the present invention has been described for a highly basic calcium sulfonate, the same applies to a highly basic sulfonate compound comprising an alkaline earth metal such as a highly basic magnesium sulfonate or a highly basic barium sulfonate. It is easily conceivable that the same action and effect can be obtained by the amount.

When the lubricant of the present invention contains a highly basic alkaline earth metal sulfonate (excluding 20 to 70% by weight), the formation of a sufficient oxide film on a wear-resistant cast iron roll is suppressed, and the surface of the roll is roughened. Has the effect of preventing
10 to 90% by weight (excluding 20 to 70% by weight) of one or two mineral oils and esters to 10 to 90% by weight (excluding 30 to 90% by weight) of the highly basic alkaline earth metal sulfonate
To 80% by weight), the above effect can be obtained even more. Both the mineral oil and the ester form a lubricating film between the roll and the rolled material, reduce the friction coefficient, and suppress the roughening of the wear-resistant cast iron roll. In addition, when the high basic alkaline earth sulfonate alone has a high viscosity and cannot be lubricated by a lubricant pump, a relatively low viscosity mineral oil or an ester or a mixture of a mineral oil and an ester is added to the lubricant. It becomes possible to adjust the viscosity so that oil can be supplied by the pump.
In this case, a mineral oil having a relatively low viscosity such as a spindle oil, a machine oil, or a motor oil is preferable. As the ester, one obtained by esterifying one or more of the OH groups in an alcohol such as 2-ethylhexanol, glycerin, trimethymerpropane, and pentaerythritol with a fatty acid having 4 to 22 carbon atoms has a relatively low viscosity. preferable. In order to sufficiently exert the effect of lowering the friction coefficient and the effect of adjusting the viscosity, it is necessary to add 10% by weight or more of the mineral oil or the ester or the mixture of the mineral oil and the ester to the lubricant of the present invention.

It should be noted that a sufficient effect can be obtained by adding not only the above-described mineral oil and ester but also an extreme pressure agent or alcohol having a relatively low viscosity to the present lubricant. It is easily conceivable.

As described above, the lubricant for preventing skin roughness according to the present invention contains the above-mentioned basic alkaline earth metal sulfonate, or one of the above-mentioned basic alkaline earth metal sulfonate and mineral oil or ester, or Combining the two types in the above range has a remarkable effect of suppressing the surface roughness of the abrasion-resistant cast iron roll. However, for these combinations, 0.1% spherical silica having a particle size of 5 μm or more and
By adding the lubricant at a rate of about 10.0% by weight, the adhesion of the present lubricant to the roll surface is improved, and a further effect of suppressing skin roughness is obtained.

The spherical silica particles used in the present invention are preferably manufactured by spraying silica from a nozzle in a state where the silica is melted by heating to 2000 ° C. or higher, quenching, and then classifying by centrifugal sedimentation. In addition, silica particles are liable to migrate to a water portion when an emulsion is formed due to the hydrophilic nature of the surface of the silica particles. However, spherical particles are less hydrophilic than silica particles having a large surface area, such as polyhedral silica,
This is because, when it is an emulsion, it has a property that it does not easily migrate to the water portion.

The reason for using the spherical silica particles in the lubricant of the present invention is that the lubricant is supplied to the roll surface by using a water injection type oil supply system. The lubricant supplied by the water injection method is formed into a forced emulsion by the turbulent flow of dilution water in the pipe, and is then sprayed onto the roll surface via a nozzle.

In the case of refueling by the water injection method, it is required that the emulsion of the lubricant adhered to the roll surface is promptly separated into the lubricant and dilution water, and only the lubricant adheres to the roll surface. However, since a highly basic alkaline earth metal sulfonate has a sulfonic acid group in its structure, it acts as an anionic surfactant and is relatively easily emulsified in water. Due to this effect, an emulsion having a small particle size is formed in the dilution water, so that the lubricant does not separate on the roll surface, and tends to be easily washed away by the roll cooling water. Also, the effect increases as the proportion of the highly basic alkaline earth metal sulfonate contained in the lubricant increases. Therefore, it is considered that if this phenomenon is improved and the present lubricant is imparted with a property that is not easily washed away by the cooling water, and if the adhesion is improved, the effect of further suppressing skin roughness can be obtained.

In order to suppress the emulsifying property of the highly basic alkaline earth metal sulfonate having the above-mentioned properties, Japanese Patent Application Laid-Open No.
There is a method disclosed in Japanese Patent No. 46298, in which an oil-soluble polymer compound is added to rolling oil to increase the particle diameter of the rolling oil emulsion and increase the adhesion to the roll surface. However, the oil-soluble polymer compound disclosed in the above-mentioned patent publication has fatty acids and / or
Or, since a diester of an aliphatic and phosphoric acid is used, there is a problem that, for example, CaCO ₃ in a highly basic calcium sulfonate causes a saponification reaction with respect to this counter ion, thereby lowering expected performance. .

The present inventors have tried to suppress emulsification by adding various substances having an emulsification suppressing effect to a highly basic alkaline earth metal sulfonate, for example, a highly basic calcium sulfonate. However, it was difficult to obtain a substance having a stable effect due to the strong reactivity of the basic component in the highly basic calcium sulfonate. Thus, the present inventors have sought and studied a substance which is stable to a basic component and has an emulsification suppressing effect as an inorganic substance having no reactivity with CaCO ₃ . As a result, the spherical silica fine particles are stable against highly basic calcium sulfonate,
In addition, they have found that they have an excellent emulsification suppressing effect.

The detailed action principle of this emulsification suppression effect is unknown, but spherical silica fine particles aggregate emulsion particles having a small particle diameter due to strong surface activity, change the emulsion particles into an emulsion having a large particle diameter, and apply a lubricant to the roll surface. It is conceivable that the particles are aggregated and adhered.
However, this spherical silica particles, if the particle size is too fine,
The effect of suppressing emulsification becomes excessive and hinders the formation of an emulsion. For this reason, in the piping before reaching the nozzle, the lubricant is separated from the dilution water, making it impossible to refuel. On the other hand, when the particle diameter of the spherical silica particles is too large, the effect of suppressing the emulsification decreases. Therefore, the particle size of the spherical silica particles is 5 μm or more and 20 μm or more.
It must be less than m. The reason why this phenomenon occurs is that when the particle size is small, the surface activity is large and the aggregation effect of the emulsion particles is strong, and when the particle size is large, the surface activity is weak and the aggregation effect of the emulsion particles is small. Something like that is possible.

It is preferable that the spherical Rishica particles used in the present invention are contained at a ratio of 0.1 to 10% by weight based on the base oil. The reason is that when the content is less than 0.1% by weight, the emulsification suppressing effect is insufficient, and when the content is more than 10.0% by weight,
This is because the effect of suppressing emulsification becomes excessive.

The lubricant of the present invention has an intrinsic viscosity at 40 ° C. by using one or two mineral oils or esters having an appropriate viscosity as the base oil regardless of whether the lubricant contains spherical silica particles. It is preferably 1000 mm ² / s or less. The reason is that a gear pump or plunger pump, which is used as a general lubricant pump as a lubricant pump, cannot supply oil due to poor suction or increased pressure loss when the viscosity of the lubricant is too high. Many.
This phenomenon is a major obstacle in stably supplying the lubricant of the present invention to the roll.

The hot rolling method of the present invention is characterized in that a lubricant of the present invention having the above-mentioned composition is used to lubricate the roll surface by a water injection type lubricant lubrication method. This is a hot rolling method, and by this method, it is possible to suppress the formation of an oxide film on the surface of a wear-resistant rolling roll.

[0027]

EXAMPLES The present invention will be described with reference to Examples and Comparative Examples. Examples 1 to 20, Comparative Examples 1 to 8 The lubricants of Examples and Comparative Examples were produced using a stainless steel heating pot having a stirrer. In the production, highly basic calcium sulfonate, mineral oil, ester and spherical silica particles were charged into a kettle at a weight ratio shown in Tables 2 and 3, and 50 to 10 were added.
Performed by stirring at 0 ° C. until uniform.
In a second stand of a six-stand mill row of a hot finishing rolling mill with a lubricant, a wear-resistant cast iron rolling roll was used under the hot rolling conditions and the lubricant oiling amount shown in Table 1 by using a lubricating oil supply system by a water injection method. Refueled.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

When hot rolling of steel is performed using the lubricant of the present invention, the formation of an oxide film on the surface of a roll of abrasion-resistant cast iron can be suppressed. Therefore, it was possible to eliminate the roll surface roughness caused by the peeling of the oxide film on the surface of the wear-resistant cast iron rolling roll, which has conventionally occurred.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location C10M 105: 72 103: 00) C10N 10:04 20:00 20:02 20:06 30:00 30:10 40 : 24 (72) Inventor Masayoshi Sakakibara 5529-8 Oba, Fujisawa-shi, Kanagawa No.308 Charman Corp. (56) References JP-A-5-306399 (JP, A)

Claims (7)

(57) [Claims] 1. A lubricant for preventing roughening of a wear-resistant cast iron rolling roll, comprising a highly basic alkaline earth metal sulfonate (excluding 20 to 70% by weight). 2. 10 to 90% by weight (excluding 20 to 70% by weight) of a highly basic alkaline earth metal sulfonate and 10 to 90% by weight of one or two of mineral oils and esters
(Excluding 30 to 80% by weight). A lubricant for preventing roughening of a wear-resistant cast iron rolling roll. 3. A highly basic alkaline earth metal sulfonate of 10 to 99.9% by weight (excluding 20 to 70% by weight) and spherical silica particles having a particle size of 5 μm to 20 μm.
A lubricant for preventing roughening of wear-resistant cast iron rolls containing 0.0% by weight. 4. 10 to 89.9% by weight (excluding 20 to 70% by weight) of a highly basic alkaline earth metal sulfonate and 10 to 89.9% by weight of one or two of mineral oils and esters
(Excluding 30 to 80% by weight) and particle size of 5 μm or more 2
A lubricant for preventing roughening of wear-resistant cast iron rolling rolls containing 0.1 to 10.0% by weight of spherical silica particles of 0 μm or less. 5. The lubricant according to claim 1, wherein the highly basic alkaline earth metal sulfonate has a base number of 100 or more. 6. A lubricant having a viscosity of 1000 mm ^{2 at} 40 ° C.
The lubricant according to any one of claims 1 to 5, wherein the lubricant is not more than / s. 7. The hot rolling of steel using a wear-resistant cast iron rolling roll, wherein the lubricant according to any one of claims 1 to 6 is applied to the surface of the roll by a lubricant injection method of a water injection system. A hot rolling method for steel, characterized by suppressing the formation of an oxide film on the roll surface by lubricating the steel.