JPH0384097A - Cold-rolling oil for steel and rolling process using the same - Google Patents

Abstract

PURPOSE:To obtain the subject cold-rolling oil having good slip resistance, seizing resistance and lubricity and giving a rolled steel plate having accurate thickness and excellent surface quality by compounding specific amounts of a phthalic acid ester, etc., and a specific sulfurized oil and adjusting the viscosity to a specific level. CONSTITUTION:The objective cold-rolling oil contains (A) >=25wt.% of an ester of phthalic acid and/or trimellitic acid and a 4-18C aliphatic alcohol and (B) 2-10wt.% of a sulfurized oil having a sulfur content of 20-35wt.% and produced by sulfurizing a mixture obtained by adding 10-35wt.% of a 8-18C olefin to oleyl oleate and has a viscosity adjusted to 5-25cst at 50 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a cold rolling oil for steel plates and a rolling method using the same.

(Prior art) Generally, rolling oil used during cold rolling of steel plates is interposed between the rolling rolls and the steel plate to prevent the occurrence of seizure defects due to direct contact between the two, and to reduce friction between the two. The ability to reduce the rolling load and rolling power is required.

In conventional rolling, rolling oils containing mineral oil, synthetic leather ester, natural oils and fats as main ingredients have been used. However, the diameter of the rolling roll is as large as 450 to 600 mm, and the rolling reduction per bath is at most about 35%; if it exceeds this, seizure will occur and impede improvements in productivity and quality.

Therefore, a method of forming a chemical conversion coating on a steel sheet in advance as shown in JP-A No. 57-112905,
A method of increasing the amount of rolling oil introduced as shown in No. 2-.15NO4 has been considered and implemented. However, these methods require pretreatment of the steel plate before rolling, and the degree of productivity improvement is low.

In addition, if a roll with a small rolling roll diameter of 200 to 300 mm is used, the rolling load can be reduced compared to conventional rolling.
It has become known that the reduction rate per pass can be increased. Since rolling using the above-mentioned small-diameter rolls has a high reduction rate and a small roll diameter, the bite angle formed between the roll and the steel sheet to be rolled is larger than in conventional rolling.

Therefore, when conventional rolling oil is used, the amount of rolling oil introduced between the roll and the steel plate to be rolled decreases due to the relationship expressed by the following equation.

Introduced oil film thickness: td-η(U+V)/αP・(1) η: Rolling oil viscosity, U・Roll circumferential speed V: Speed of rolled steel plate, P: Yield stress of rolled steel plate, a: Rolled steel plate and the bite angle of the rolls. Especially when rolling steel sheet coils, the rolling speed at the leading and trailing ends of the coil is low, so the amount of rolling oil applied to the coil is significantly reduced, resulting in insufficient lubrication.

The rolling oil used in such cases is required to have characteristics that do not reduce the amount introduced or prevent oil film from breaking.

On the other hand, as a lubrication method for preventing slip and seizing defects, Japanese Patent Application Laid-Open No. 1-15215 proposes a method using a low-viscosity precoat oil containing a sulfur compound. However, since the precoat oil is thinly stretched with each rolling pass, its effect is insufficient, and seizure occurs during rolling under high pressure.

(Problems to be Solved by the Invention) The viscosity of the cold rolling oil for steel sheets must be suppressed to prevent slippage, so it cannot be made to have a very high viscosity.

Further, conventional rolling oils mainly composed of synthetic esters, natural oils and fats have low viscosity, and when used in small-diameter roll rolling, a sufficient amount cannot be obtained. Direct contact between the rolling rolls and the steel plate can cause seizure defects, and the rolling load can become extremely high, making it impossible to roll the plate to the set thickness, resulting in poor thickness, etc. There are quality issues.

Further, due to the change in rolling speed I, the introduction amount changes greatly, and the variation in rolling load becomes large, especially in the acceleration/deceleration section.

As a result, rolling becomes unstable and steady rolling (high speed rolling)
It takes time to reach this point, resulting in lower production efficiency.

Furthermore, when the speed of the steady rolling section is increased, the generation of frictional heat increases, which causes a decrease in the amount of rolling oil introduced due to a decrease in the viscosity of the rolling oil, a decrease in the heat resistance and strength of the oil film, and seizure. Therefore, the rolling speed of the steady rolling section cannot be sufficiently increased, and the production efficiency further decreases.

The present invention has been made in order to solve such conventional problems, and when cold rolling a steel plate with a large rolling pass reduction rate and a small number of passes, the amount of variation in rolling load due to changes in rolling speed can be reduced. It is an object of the present invention to provide a rolling oil and a rolling method that can obtain an excellent lubrication state with less occurrence of seizure defects.

(Means for Solving the Problems) In order to solve the above problems, in the present invention, one or more esters of phthalic acid and/or trimellitic acid and an aliphatic alcohol having 4 to 18 carbon atoms are used. 25vf%
or more and carbon number 8 to oleyl oleate
A cold rolling oil for steel sheets is made by adding 2 to 10 WL% of sulfurized oil to which a mixture containing 10 to 35 wt% of No. 18 olefins is sulfurized to have a sulfur content of 20 to 35 wt%.

Further, in the rolling method of the present invention, a multi-roll mill with rolling rolls having a diameter of 150 to 400 mm is used, and the above-mentioned rolling oil is supplied to perform strong reduction rolling.

(Function) The present inventor completed the present invention as a result of various studies based on the following ideas.

(1) To reduce load fluctuations, lower the viscosity of rolling oil. This is because the lubrication state during rolling is in a mixed region of boundary lubrication and fluid lubrication, and the lubrication state changes greatly as the amount of introduced oil increases or decreases.

Therefore, by using low-viscosity oil, the amount of introduced oil is reduced, and rolling is performed in the boundary lubrication region where there is little change in the friction coefficient.

(2) It was thought that the oil-based agent that uses an oil-based agent whose amount of introduced oil does not change much due to changes in speed will have a large viscosity drop due to temperature, and the amount of introduced oil will not increase significantly during high-speed rolling at high temperatures.

(3) In order to prevent seizure, a sulfur (hereinafter referred to as S)-based extreme pressure agent that can maintain its effectiveness up to high temperatures is used. At this time, if the friction coefficient is lowered more than necessary, slip will occur, so the friction coefficient is adjusted by adjusting the amount of S, the type of raw oil, and the blending amount.

The first invention is a rolling oil containing an aromatic carboxylic acid ester (phthalic acid ester, trimellitic acid ester) and sulfurized oil. Esters of phthalic acid and trimellitic acid with aliphatic alcohols have larger viscosity changes with temperature changes than commonly used aliphatic carboxylic acid esters. It was also found that it has high thermal stability and is suitable for the present invention.

In particular, when the aliphatic alcohol has 4 to 18 carbon atoms,
Suitable as an oily agent for rolling oil. That is, if it is less than 4,
It has poor lubricity and a high coefficient of friction, making it prone to seizure. Furthermore, if the oil exceeds the viscosity, the viscosity becomes high and the change in the amount of introduced oil becomes large, making it impossible to achieve the desired reduction in load fluctuation.

In addition, the amount of these esters contained in the rolling oil is 2
If it is less than 5wt%, the effect will not be fully exhibited, so 2
The content is preferably Svj% or more, and more preferably 3Svt% to 7Svt%. The higher the content of these esters, the more desirable it is, but if the content exceeds 7 Sit%, the effect will be saturated, so the upper limit was set at 75vt%.

Specifically, the aromatic carboxylic acid esters shown in the present invention include diisobutyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate (vinicizer 80), didecyl phthalate (vinicizer 85), and didecyl phthalate (vinicizer 105). , ditridecyl phthalate (Vinicizer 20), dilauryl phthalate, distearyl phthalate, dioleyl phthalate, triisobutyl trimellitate, tributyl trimellitate, tri-2-ethylhexyl trimellitate (Trimex T-08), trioctyl trimellitate (trimellitate) MEX N-08), trinonyl trimellitate (TRIMEX T-09), l-triisodecyl trimellitate (TRIMEX T-10), (() is a trade name of Kao Corporation).

Sulfurized oil is an extreme pressure additive that reacts with steel plates and rolls under high temperature and high surface pressure, producing iron sulfide, etc., and exerting a lubricating effect. However, when an olefin is sulfurized, the lubricating effect of which varies greatly depending on the raw material to be sulfurized and the amount of S, a sulfurized oil with excellent seizure resistance can be obtained, but the coefficient of friction is undesirably high. Furthermore, when oil or fat or oleyl oleate is sulfurized, the friction coefficient is low, but the seizure resistance is poor. In particular, sulfurized fats and oils have a low amount of S and have poor seizure properties.

When a mixture of oleyl oleate and olefin is sulfurized, a sulfurized oil with excellent seizure resistance and a low coefficient of friction can be obtained. In this case, if the ratio of olefin to oleyl oleate is less than ]OW[%, the seizure resistance will be poor and 3Sv
If it exceeds t%, the coefficient of friction will increase, which is not preferable. The number of carbon atoms in myo-olefin is preferably 8 to 18, and if it is less than 8, separation and decomposition of the added S becomes significant and the steel plate becomes stained, which is not preferred. Moreover, if it exceeds 11, the amount of S to be sulfurized is small and the seizure resistance is deteriorated, which is not preferable.

If the amount of sulfurized oil in the rolling oil is less than 2vt%, excellent seizure resistance and friction coefficient reduction effects cannot be obtained. Also, 10vL%
If it exceeds this, the effect not only becomes saturated, but also remains as dirt on the steel plate after rolling, impairing the cleanliness of the steel plate, which is not preferable.

The viscosity of the rolling oil of the present invention is 5 to 25 cs at 50°C.
The reason why the amount of oil introduced is less than 5 cSL is too small and the effects of the aromatic carboxylic acid ester and sulfurized oil are not fully exerted and seizure occurs. This is not preferable because the load fluctuation range becomes large.

As long as the rolling oil of the present invention satisfies the above contents,
In addition to aromatic carboxylic acid esters and sulfurized oils, commonly used mineral oils, fats and oils, fatty acid monoesters, phosphoric acid esters, and the like may be contained.

The same applies to emulsifiers, rust preventives, and antioxidants.

The second invention relates to a rolling method for effectively demonstrating the performance of the rolling oil of the first invention.

For large diameter rolls with a diameter exceeding 400 mm, the biting angle σ (expressed by equation (2)) is small and the introduced film thickness shown by equation (1) is large, so the rolling oil of the present invention is Performance is not fully demonstrated. Also, excessive lubrication may occur,
Even when the rolling oil of the present invention is used, slip occurs, which is not preferable.

σ-F 0/R...(2) r: rolling reduction ratio, ho: plate thickness of rolled steel plate, R: rolling 0-small radius Also, for small diameter rolls with a diameter of less than 150 mm, the Since rolling is possible with a rolling load and problems such as fluctuations in rolling load during acceleration and deceleration do not occur, the performance of the rolling oil of the present invention is not fully exhibited. Regarding the rolling reduction rate,
As shown in the above formula (2), when the rolling reduction is small,
a is small (even if conventional rolling oil is used, a sufficient film thickness of rolling oil can be obtained, so the performance of the rolling oil of the present invention is not fully exhibited).

Furthermore, if the rolling reduction ratio is small, the number of rolling passes increases, making it impossible to achieve the desired high efficiency rolling.

In addition, in the rolling method of the present invention, the rolling mill is limited to a multi-roll mill using auxiliary rolls. This is because it exhibits particularly excellent performance against.

(Example) Various rolling oils according to the present invention were prepared, and the present invention was evaluated by comparing these with conventional rolling oils and comparative examples not included in the present invention.

Conventional rolling oil mineral oil is used as the base oil, and to this, 25W [%] of beef tallow, 15wt% of stearic acid octyl ester, and 2vL of oleic acid are added.
%, an emulsifier, an antioxidant, and a rust preventive agent were added in a total amount of 5vj%.

Examples 1 to 12 Rolling oils of the present invention were prepared by adding synthetic esters shown in Table 1 and sulfurized oils. The viscosity of these rolling oils is also shown in the same table.

Comparative Examples 1 to 13 Comparative examples were created by adding the synthetic esters and sulfurized oil shown in Table 1. The viscosity of these rolling oils is also shown in the same table.

Table Experiment ■ In order to compare the occurrence of seizure on the friction surface and the friction coefficient when using the rolling oil of the present invention with conventional rolling oil and comparative examples, a friction test was conducted using a two-cylinder rolling and sliding tester. carried out.

The samples used in the experiment were the above-mentioned conventional rolling oil and rolling oil to which the synthetic ester sulfurized oil shown in Table 1 was added (other compositions include 3 wf% oleic acid, 2 wt% trilauryl phosphate, 3 wt% emulsifier, and 4% emulsifier). Rust agent lit%, antioxidant 1wL%, balance mineral oil) were used.

Test Conditions The test conditions were as follows: the coefficient of friction was calculated from the rotational torque acting on the upper roll, and the change due to rotational speed was measured. Further, the test temperature was increased from 50°C to 200°C at a rotational speed of 20 rpm, and the occurrence of seizure was observed.

Upper roll shape: 125Φ×10' Material: Low carbon steel Surface roughness: Ra 0.2μm Lower roll shape: 100ΦX 30' Material: Tool steel (SKD mouth, hardened/tempered material) Surface roughness: Ra 0.1μm Rotation Speed: 20 to 8 GO rpm (upper and lower rolls rotate at the same time) Pressing load: 200 Jf Test temperature: 50. Rolling oil supply amount at various temperatures: too, 150, and 200'O: [Table 2 shows the results of the IQ ml/min oil supply test of the liquid to the upper and lower rolls.

Table *1 0:0.05 Not 1KΔ: 005~0, l ×: 0.1 or more As is clear from Table 2, the rolling oil of the present invention has a low coefficient of friction in low-speed sliding conditions. In addition, seizure does not occur even at high temperatures, and the coefficient of friction changes little with speed.

Experiment ■ Rolling experiments were conducted under the following rolling conditions using the conventional rolling oil used in Experiment I and the rolling oil of Example 3, and the results were as follows: slip occurrence during rolling, variation in rolling load, presence or absence of seizure flaws on the surface of the steel plate, Changes in thickness were observed and measured, and slip resistance, seizure resistance, and load variability were evaluated. Further, rolling experiments were conducted with different diameters of the rolling rolls, and similar evaluations were conducted.

Rolling test conditions Rolling mill Double 6-layer type (6Hi) Reversible rolling mill Roll diameter: ■100 am◆ ■150 questions◆ ■400 am◆ ■5 oil am◆ (In this case, 4-layer type) Roll surface roughness: R10, 4μm intermediate roll diameter: 5HmmΦ Backup (auxiliary) roll diameter: 1200mmΦ
Rolled material: Low carbon steel, hot rolled, pickled material (thickness 21m + ax width 12flOmm x weight I 5TO
IJ) Rolling ratio: 3 passes with a rolling ratio of 40% in each pass Rolled plate thickness: 2.3 aua → 1. Hmm-*0.83mm
+ 0.50111111 Reduction rate 40% 4
0% 40% rolling speed: steady state rolling speed 100
0 m/ll1in rolling oil supply: 3% emulsion supplied onto the steel plate from the a-ru and entry side The experimental results are shown in Table 3.

The above experiments show that the rolling oil of the present invention has excellent anti-slip properties and anti-seizure properties, and exhibits good lubricity. Also,
Using this rolling oil, the rolling roll diameter is 150 to 400 mm.
It can be seen that by rolling with a rolling mill of 1, it is possible to roll with excellent plate thickness accuracy without causing slivers or seizure.

(Effects of the invention) By using the rolling oil and rolling method of the present invention, the occurrence of slip can be prevented, the increase in rolling load at low speeds is small, excellent plate thickness accuracy can be obtained, and surface quality is improved without the occurrence of seizure defects. It is possible to roll steel sheets with high efficiency.

Claims (1)

[Claims] 1. Phthalic acid and/or trimellitic acid and carbon number 4 to 18
A mixture containing 25 wt% or more of one or more esters with aliphatic alcohols and 10 to 35 wt% of an olefin having 8 to 18 carbon atoms based on oleyl oleate is sulfurized to reduce the sulfur content. A cold rolling oil for steel sheets containing 2 to 10 wt% of sulfurized oil of 20 to 35 wt% and having a viscosity of 5 to 25 cSt at 50°C. 2. A rolling method using a multi-roll mill with rolling rolls having a diameter of 150 to 400 mm and supplying the steel plate cold rolling oil according to claim 1 to perform strong reduction rolling.