JP2689827B2 - Cold rolling method for steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to a cold rolling method for steel products,
In particular, the present invention relates to a lubrication rolling method for a steel material for significantly extending the roll life and obtaining a high-quality product in rolling using a roll for rolling work having a chromium or chromium alloy plating layer on the surface of the roll body.

[0002]

2. Description of the Related Art In the rolling of steel materials such as stainless steel and carbon steel, wear-resistant rolls have been developed in which the surface of the roll body is coated with a chromium or chromium alloy plating layer for the purpose of significantly extending the roll life. As an example of such a wear-resistant roll, a cold rolling roll is disclosed in JP-A-60
-196207, JP-A 61-202707, JP-A 62-16808, JP-A 62-168605,
Japanese Unexamined Patent Publication No. 2-58806, of JP-A-2-200307
Some are described in each publication . The wear-resistant roll for hot rolling is described in Japanese Patent Publication No. 2-54169.

However, when such a chromium plating layer or a chromium alloy plating layer is rolled by using a rolling work roll having a roll body surface, a flaw (heat) which is considered to be caused by seizure with the roll on the surface of the steel material. Scratch defects) occur remarkably. Further, in severe rolling conditions, roll wear was large and rolling schedules were restricted.

With the recent advancement of high grade steel materials, not only stainless steel sheets but also carbon steel sheets are required to have a beautiful surface texture. Therefore, when surface flaws occur on rolled products, they need to be ground and polished. Or, in extreme cases, I have no choice but to scrap. Therefore, the occurrence of heat scratches has become a major problem in rolling steel products.

As a cause of this heat scratch flaw, it is considered that the oxidation protection film on the surface of the steel material is peeled off. For example, high chrome steel represented by stainless steel is
By containing 13% or more of Cr, a stable chromium oxide protective film is formed on the surface of the steel to passivate the surface, thus exhibiting excellent corrosion resistance. However, since this surface oxide film is extremely thin, it easily peels off when subjected to plastic working during rolling, which causes deterioration of corrosion resistance and causes seizure.

In hot rolling of carbon steel, low temperature rolling,
During high-load rolling such as high-pressure rolling, a sufficient oxidation protection film is not formed on the surface of the steel material, or even if an oxidation protection film is formed, it will sufficiently follow the work deformation when subjected to large plastic working. This is not possible, and the surface oxide film is likely to crack or peel off.

However, the fact that the occurrence of heat scratches is particularly remarkable when a rolling work roll having a chromium or chromium alloy plating layer is used indicates that the main cause of the occurrence of these flaws is on the roll side. ing.

Conventionally, in order to deal with such a problem,
Lubricants have been supplied to rolling rolls and their reinforcing rolls. The purpose of using the lubricant is to reduce the frictional force between the rolling roll and the steel material to prevent seizure,
It is to improve the quality of rolled products by preventing the roughening and abrasion of rolls.

[0009] As such a lubricant, JP-A-47- 1
No. 8907 discloses that natural fatty oils have a total content of 0.1 to 10%.
Lubricating compositions have been proposed which incorporate a small amount of a water displacement agent by weight and optionally a mineral lubricating oil. As the water displacing agent, an oil-soluble sulfonic acid salt (eg, a metal salt of petroleum sulfonic acid) is used. Further, a lubricant in which finely divided calcium carbonate of about 10 μm or less is dispersed in water or a lubricating base oil is disclosed in JP-B-62-14598 and JP-B-62-391.
No. 98 and JP-B-62-39199.

However, these lubricants are intended for lubrication during rolling of carbon steel, and when they are used for hot rolling of stainless steel, the material to be rolled is severely seized on the surface of the work roll for rolling, resulting in rolling products. Cause flaws. In addition, since the work roll for rolling has a large abrasion, there is a problem that the rolling efficiency is extremely reduced.

As a lubricant for rolling stainless steel, one in which iron oxide powder is dispersed in lubricating oil is disclosed in JP-A-63-254195, and graphite powder is viscous in JP-A-1-167396. Those dispersed in an aqueous solution have been proposed.

However, even if the iron oxide powder is dispersed in order to suppress the state of direct metal-to-metal contact, it is possible to sufficiently prevent seizure and roll wear between the work roll for rolling and the material to be rolled. Has not been done. Graphite has an extremely low coefficient of friction, which causes poor biting of the material to be rolled and slip during rolling, so that it cannot be contained in an amount sufficient to exhibit the seizure prevention effect and the wear reduction effect. Was.

[0013]

DISCLOSURE OF THE INVENTION An object of the present invention is to prevent seizure flaws (heat) of a steel material which is generated when rolling is performed using a rolling work roll having a chromium or chromium alloy plating layer on the surface of a roll body. It is an object of the present invention to provide a cold rolling method for a steel material, which can prevent scratches and at the same time reduce roll wear, thereby significantly extending roll life and obtaining high-quality rolled products.

[0014]

The present inventors Means for Solving the Problems] are seizing scratches the roll and the steel in the rolling of steel with a rolling work rolls having a chromium or chromium alloy plating layer on the surface of the (heater toss clutch flaws) As a result of extensive studies on a lubrication method capable of preventing the above, it was found that the above object can be achieved by using a lubricant containing a highly basic Ca sulfonate, and the present invention has been completed.

According to the present invention, a lubricant containing 20 to 70% by weight of a highly basic Ca sulfonate is used in rolling a steel material using a work roll having a chromium or chromium alloy plating layer on the surface of a roll body. The gist is a cold rolling method for a steel material, which is characterized in that the steel material is rolled while being supplied to the roll surface. As another aspect of the present invention, in the rolling of a steel material using a work roll having a chromium or chromium alloy plating layer on the surface of a roll body, high basic C
a sulfonate and a total of 20% by weight or less of the total amount of sulfonate metal salts other than Ca sulfonate metal salts other than Ca.
You may roll, supplying the lubricant containing -70 weight% to the said roll surface.

[0016]

The roll for rolling operation used in the method of the present invention is a roll having a chromium or chromium alloy plating layer on the surface of the roll body. Typically 5 to 130 μm for this type of roll
A chromium plating layer or a chromium alloy plating layer having a thickness of 1 is applied. For chromium alloy plating, Cr-Ni, Cr-
There are W, Cr-Fe, Cr-Mo, Cr-V, Cr-Re, Cr-Sn and the like, which means one containing Cr 50% by weight or more.

The roll having a chromium plating layer also includes a roll plated with chromium containing fine particles such as eutectoid chromium plating. Eutectoid chrome plating is so-called ultra-hard plating, in which C is codeposited in the film during deposition and chromium carbide is deposited, or hard particles of 1 μm or less in advance.
(Eg, SiC particles) is mixed with a plating solution and co-deposited to improve the wear resistance of chromium plating.

On the surface layer of the roll having a chromium plating layer or a chromium alloy plating layer on its surface, a stable and high hardness oxidation protection film (made of chromium oxide [Cr ₂ O ₃ ]) having a thickness of about 40 to 100 Å is formed. As a result, the oxidation protection film suppresses wear of the roll. However, during rolling, this very thin oxidation protection film partially peels off, and at the same time, the oxidation protection film easily peels off on the steel side as well, which causes direct contact between the rolled steel and the metal, causing seizure. It became clear that heat scratches occurred. Due to this, heat scratches frequently occur when a chromium or chromium alloy plating roll is used.

According to the present invention, the occurrence of this heat scratch flaw is suppressed by using a lubricant containing a highly basic Ca sulfonate. Ca sulphonate is a Ca salt obtained by neutralizing alkyl aromatic sulphonic acid, and when this Ca sulphonate is reacted with CaO or Ca (OH) _{2 in} the presence of carbon dioxide gas, a highly basic Ca sulphonate is formed. To do. Highly basic Ca sulphonate contains 3 to 15 times more Ca than normal Ca sulphonate, and this Ca is mainly in the form of calcium carbonate (CaCO ₃ ). 150
Å The following colloidal forms a colloidal dispersion dispersed in oil. The amount of excess Ca in the highly basic Ca sulfonate can be indicated by the base number defined in JIS-K2501. The highly basic Ca sulfonate used in the present invention has a base number of 40 mg-KOH / g or more.

Since the highly basic Ca sulfonate has excellent heat resistance, when it is used as a lubricant, it does not completely burn or decompose even during hot rolling of steel materials, and it is close to a fluid or a fluid. It exists in a state and can contribute to lubrication. In addition, the highly basic Ca sulfonate is
It has a high reactivity with the acidic chromium oxides (Cr ₂ O ₃ ) existing on the roll surface, and forms a lubricious reaction layer on the roll surface that is difficult to peel off during plastic working, thus ensuring direct contact between the roll and steel. It has been found that effective prevention further improves lubricity.

In addition, as described above, the highly basic Ca sulfonate contains fine particles of Ca salt (calcium carbonate) in oil as a colloidal dispersion having a particle size of 150 Å or less. The finely dispersed calcium carbonate has the effect of physically suppressing metal-to-metal contact between the steel material and the roll. In addition, the fine calcium carbonate also acts as a carrier (carrier) of the highly basic Ca sulfonate, which is the main component of the lubricating action, and even when the high pressure during hot rolling, the fine particles become rolls for rolling work. Since it is introduced into the frictional interface with the material to be rolled in a uniform state, the highly basic Ca sulfonate has a remarkably high lubricating effect, and suppresses the direct contact state between the metals at the frictional interface to prevent seizure and at the same time. It is possible to greatly reduce the wear of the roll.

With the above operation, according to the method of the present invention,
In rolling using a rolling work roll having a chrome or chromium alloy plating layer, it is possible to prevent seizure and heat scratch flaws on the work roll for rolling steel, and to significantly reduce roll wear. It is possible to secure high quality of rolled products. This effect is particularly remarkable in hot rolling, but the effect of the present invention is also exerted in cold rolling.

The raw material alkylaromatic of the highly basic Ca sulfonate used in the present invention is not particularly limited, and like the conventional product, the lubricating oil fraction of mineral oil and synthetic compounds (eg, alkylbenzene, polyolefin to benzene are alkylated). Or a dinonylnaphthalene).

The highly basic Ca sulfonate is contained in the lubricant used in the present invention in a proportion of 20 to 70% by weight. If this content is less than 20% by weight, the amount of roll wear increases, and it is not possible to sufficiently prevent seizure and the occurrence of heat scratch defects. On the other hand, if the content of the highly basic Ca sulfonate exceeds 70% by weight, the lubricant becomes highly viscous and it becomes difficult to supply the lubricant, so the content of the highly basic Ca sulfonate is set to 20 to 70% by weight. The preferred content of the overbased Ca sulfonate is 30 to 60% by weight.

The base number of the highly basic Ca sulfonate used is 40 mg-KOH / g or more, and the one having a base number of 200 to 500 mg-KOH / g is excellent in the ability to prevent seizure and heat scratches and abrasion resistance. Therefore, it is particularly preferable. Base number is 200
When the amount is less than mg-KOH / g, the amount of calcium carbonate as a carrier for improving the introduction property of the highly basic Ca sulfonate to the friction interface is small, and the introduction amount of the highly basic Ca sulfonate to the friction interface is reduced. It may not be possible to sufficiently reduce roll wear and completely prevent seizure and heat scratch defects. On the other hand, the base number is 500 mg-K
A highly basic Ca sulfonate exceeding OH / g cannot be produced at the current technical level, though it has a proper function as a rolling lubricant, such as a viscosity. However, if it becomes possible due to manufacturing technology, a base number of more than 500 mg-KOH / g could be used. As the highly basic Ca sulfonate, those having various basicities are commercially available, and commercially available products may be used.

The lower limit of the base number depends on the conditions such as concentration and viscosity when the lubricant is supplied, but especially when the lubricant is supplied at a high viscosity or in a state close to the stock solution, or under low load rolling conditions. Even if the value is less than 200 mg-KOH / g, sufficient lubricating effect can be exhibited. However, if the base number is less than 40 mg-KOH / g, the lubricating effect will be insufficient in any case.

As described above, in the method of the present invention, a high base having excellent reactivity with an acidic chromium oxide (Cr ₂ O ₃ ) protective film formed on the surface of a roll plated with chromium or a chromium alloy. It is characterized by using a lubricant containing a specific amount of the basic Ca sulfonate, and the presence of this highly basic Ca sulfonate is important for achieving the above-mentioned effects of the present invention.

Particle size contained in highly basic Ca sulfonate 1
Calcium carbonate of 50 liters or less is spontaneously precipitated in the process of producing highly basic Ca sulfonate, and forms a colloidal dispersion in oil. The colloidally dispersed calcium carbonate has a particle size of 1 to 10 μm which is separately prepared as described in Japanese Patent Publication No. 62-14598.
The action and effect are clearly different from those of the prior art lubricant in which about m of finely divided calcium carbonate is dispersed in a lubricating base oil. In this prior art lubricant, the calcium carbonate powder itself exerts a lubricating effect.

On the other hand, calcium carbonate having a particle size of 150 Å or less, which is precipitated as a salt in the highly basic Ca sulfonate, does not have any lubricating effect. In order to more easily exert the effect (forming a lubricious reaction layer on the protective film of acidic chromium oxide to reduce friction and prevent peeling of the chromium plating layer), friction with highly basic Ca sulfonate is used. It mainly acts as a carrier that carries to the interface, and plays a role in assisting the introduction and reactivity of highly basic Ca sulfonate under a high surface pressure frictional interface. It is also considered to have a role of suppressing the physical direct contact state of the friction interface.

Thus, highly basic Ca showing high lubricity
Due to the synergistic effect of the sulfonate and the colloidal calcium carbonate with a particle size of 150Å or less, which acts mainly as a carrier, the effect of significantly improving seizure resistance and roll wear resistance during rolling using chromium or chromium alloy plating rolls It will be demonstrated.

The lubricant containing 20 to 70% by weight of the highly basic Ca sulfonate used in the method of the present invention can be prepared by blending the highly basic Ca sulfonate with a commonly used lubricating base oil. A lubricant consisting of 20 to 70% by weight of highly basic Ca sulfonate and the balance of lubricating base oil can be used satisfactorily, but if necessary, other solid lubricants, extreme pressure additives, antioxidants, pour points Depressant, viscosity index improver, etc. 1
One kind or two or more kinds can be further blended.

Suitable examples of lubricating base oils include mineral oils,
Fats and oils such as synthetic lubricating oil, rapeseed oil and lard oil, higher fatty acids and their esters, etc. may be mentioned.

Examples of solid lubricants include graphite, molybdenum disulfide, boron nitride, mica, talc and the like.

Examples of extreme pressure additives include sulfur-based extreme pressure additives such as sulfurized fats and oils, sulfide mineral oils, dinonyl polysulfide, and phosphoresidue extreme additives such as tricresyl phosphate and dioctyl phosphate.

Examples of antioxidants include methylene-4,4
Examples thereof include bisphenols such as -bis (2,6-di-tert-butylphenol), alkylphenols such as di-tert-butylcresol, and naphthylamines. Examples of the pour point depressant and the viscosity index improver include polymethacrylate, polyolefin and the like.

The solid lubricant is added in an amount of about 1 to 10% by weight, the extreme pressure additive is added in an amount of about 1 to 15% by weight, and the antioxidant is added in an amount of about 0.01 to 1.0% by weight. The addition amount of each of the point depressant and the viscosity index improver is about 1 to 5% by weight.

The lubricant used in the present invention may contain other sulfonates such as Ba sulfonate and Mg sulfonate. That is, if the base number does not change significantly, a part of Ca sulfonate is mixed with Ba sulfonate, Mg
Even if it is replaced with another sulfonate metal salt such as sulfonate, almost the same effect can be obtained under low load rolling conditions. However, considering that the lubricating effect of Ba sulfonate and Mg sulfonate per unit amount is smaller than that of Ca sulfonate, it is preferable that the amount of the sulfonate metal salt other than Ca is 10% by weight or less based on the total amount of sulfonate.

The method of supplying the lubricant containing the highly basic Ca sulfonate to the rolling roll having the chromium or chromium alloy plating layer on the surface is not particularly limited. For example, the lubricant may be directly supplied to the rolling work roll.
In the case of a multi-stage rolling mill, the lubricant may be supplied to other rolls such as a reinforcing roll and an intermediate roll, and the lubricant may be supplied to the rolling work roll via this roll.

The lubricant supply means may be appropriately selected from known supply means. Either method can sufficiently achieve the effects of the present invention. For example, in hot rolling, depending on the required viscosity and concentration, an air atomizing method in which it is mixed with compressed air and supplied in the form of a spray, a water injection method in which it is mixed and supplied with water, or even heated steam is used. A steam atomization method or the like that is atomized and supplied can be adopted. In the case of cold rolling, it is often the case that a lubricant is mixed with water in advance to form an emulsion, and this is sprayed to be supplied. The supply system in this case includes a direct oil supply system, a circulating oil supply system, and a hybrid system (mixing system of the former two), and any of them may be adopted. Of course, a method of supplying the undiluted solution as it is may be used, and a general oil supply method other than the above may be adopted. When supplied in undiluted form, the lubricant may be made water-soluble to make it nonflammable before use.

In the rolling method of the present invention, not only general stainless steel materials such as ferritic and austenitic stainless steels but also high corrosion-resistant stainless steel materials (for example, 20% Cr steel) containing 20% by weight or more of Cr used for automobile exhaust gas materials are used. Two
0% Cr-5% Mo steel, 20% Cr-5% Al steel, etc.)
In particular, the effect is particularly remarkable in the rolling process, the low-temperature rolling of carbon steel, and the high-load rolling such as high-pressure rolling. Of course, even if it is applied to a general carbon steel material or a rolling method at the time of normal rolling, its effect is great. The rolling method of the steel material of the present invention is not limited to the rolling of the steel sheet, but can be widely applied to the cold rolling of steel materials of various shapes such as steel pipes and shaped steels, and in any case, the above-mentioned effects are exhibited. Needless to say.

[0041]

Next, a description will be given of a specific embodiment. Reference Example Reference Examples 1 to 8 shown in Table 1, Comparative Examples 1 to 3, Conventional Examples 1 and 2
The above 13 kinds of lubricants for hot rolling were prepared by mixing the components at a predetermined ratio using a homomixer, and rolling tests were conducted using the lubricants.

The rolling mill used was a four-stage hot strip rolling mill of the hot strip rolling mill line shown in FIG. 1. The rolling work roll 2 had a body made of chromium alloy (Cr-1% Ni) plating. It had a layer (plating thickness 50 μm). In FIG.
Reference numeral 1 is a lubrication supply header, 3 is a steel plate to be rolled, and 4 is a reinforcing roll.

In the rolling test, each lubricant shown in Table 1 was supplied to each rolling opportunity (rolling amount 2500 tons and 1100 tons, respectively) of carbon steel and stainless steel (SUS 304), and after rolling, The product properties (rolled product flaws, especially the presence or absence of heat scratch flaws) and roll wear amount (maximum wear depth of the upper and lower rolling work rolls were measured and displayed as an average value) were examined.

The lubricant is supplied by a water injection type supplying device 1 by diluting it to a concentration of about 0.1 to 0.5% and supplying a pressure of 3 to 4 kgf / mm ² directly to a rolling roll as shown in the figure. went.

The test results are shown in Table 2 (carbon steel) and Table 3 (stainless steel). According to the rolling method of the present invention, heat scratches did not occur on the surface of the steel sheet in any of the steel types. It was also confirmed that the amount of roll wear was significantly reduced.

In a rolling situation in which heat scratches are more likely to occur, such as stainless steel rolling, the present invention example 4,
It is also understood from the test results that the lubricant containing 30 to 60% by weight of the highly basic Ca sulfonate having a base number of 40 mg-KOH / g or more, like the lubricants 5 and 6, exerts a particularly great lubricating effect. To be done.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

[Table 3]

(Example) Twelve kinds of cold rolling lubricants of Examples 1 to 8 of the present invention, Comparative Examples 1 to 3 and Conventional Example 1 shown in Table 4 were prepared in the same manner as in Reference Example .

The rolling mill used was a four-stage cold rolling mill for a cold rolling mill mill line, and the rolling work roll had a chromium plating layer (plating thickness 20 μm) on the body. The lubricants shown in Table 4 are carbon steel, stainless steel (SUS
304) each rolling chance (rolling amount about 2000 tons,
1000 tons) was supplied to a rolling roll, and the product properties after rolling and the amount of roll wear were examined in the same manner as in Example 1. In this example, the lubricant was directly supplied to the rolling roll in an emulsion state by a circulating oil supply system.

As a result of the rolling test, it was confirmed that the generation of heat scratches was prevented in both cold rolling of carbon steel and stainless steel. In addition, compared to the conventional example (using commercially available cold rolling oil as it is), the amount of roll wear was reduced to about 1/2 in any rolling, and as a result of long-term use for 1 month, the roll unit was about 1 /. Reduced to 3. In addition, the amount of rolling can be increased as the number of roll changes decreases.

[0053]

[Table 4]

[0054]

As described above, according to the method for rolling a steel material of the present invention, it is used for rolling work having a chromium plating layer or a chromium alloy plating layer on the surface of the roll body where heat scratches are likely to occur conventionally. In rolling processing using rolls, it is possible to significantly reduce the occurrence of surface flaws such as heat clutch flaws on the steel material and roll wear.As a result, the life of the roll is greatly extended and high quality product quality is achieved. Obtainable. Further, there is no need to care for the product after rolling, and the process is simplified.

[Brief description of the drawings]

FIG. 1 shows an example of a hot rolling lubrication method of the present invention.

[Explanation of symbols]

 1: Lubricant supply header 2: Roll for rolling work 3: Steel plate 4: Reinforcing roll

Claims (2)

(57) [Claims] 1. A lubricant containing 20 to 70% by weight of highly basic Ca sulfonate is supplied to the roll surface when rolling a steel material using a work roll having a chromium or chromium alloy plating layer on the surface of a roll body. A method for cold rolling a steel material, which comprises rolling while rolling. 2. In rolling steel using a work roll having a chromium or chromium alloy plating layer on the surface of a roll body, a highly basic Ca sulfonate and Ca other than 10% by weight or less of the total sulfonate metal salt content are used. Rolling while supplying a lubricant containing a total of 20 to 70 wt% of a sulfonate metal salt to the roll surface,
Cold rolling method for steel products.