JPH06134507A - Lubricant for hot working of stainless steel - Google Patents

Abstract

PURPOSE:To provide the products which are free from surface flaws by preventing the seizure of a stainless steel to working rolls by a lubricant. CONSTITUTION:This lubricant is prepd. by dispersing 1 to 30wt.% iron oxide and 1-30wt.% metal peroxide at 2-30wt.% total dispersion weight into a viscous aq. soln. The iron oxide and metal peroxide are preferably fine powders of <=10mum grain size at >=90wt.% respectively. The aq. viscous soln. is preferably prepd. to 10 to 500 poise viscosity by addition of a high-polymer thickener. Then, the metal peroxide exhibiting an oxidation effect coexists with the iron oxide, by which the metal touch between the stainless steel and the working rolls is prevented and the thermally worked products having the favorable surface characteristics is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubricant suitable for obtaining a product having good surface properties by preventing seizure of stainless steel on a working roll during hot working of stainless steel.

[0002]

2. Description of the Related Art Since stainless steel products are required to have a clean surface, it is necessary to prevent surface scratches in the manufacturing process as much as possible. Surface scratches on stainless steel products are caused by various factors in the steelmaking process, hot rolling process, cold rolling process and the like. Among them, in the hot rolling process, the stainless steel plate is often seized on the rolling roll to cause surface scratches. A stainless steel sheet with surface scratches is not suitable for a mirror-finished application even if the surface scratches are mild. Also, if the degree of scratches is significant, it is returned to the steelmaking stage as scrap, and the yield as a steel plate decreases. When shipping a stainless steel plate with surface scratches as a product requiring a good surface condition, it is necessary to remove the surface scratches by a polishing process such as buffing. However, if the occurrence of surface scratches in the rolling process can be suppressed, the polishing process can be reduced or omitted, and the productivity is improved.

In order to prevent the occurrence of surface scratches caused by seizure during hot rolling, various studies have been conventionally conducted on reducing roll load by adjusting rolling conditions, improving material of rolling rolls, improving lubricants, and the like. It is being appreciated. For example, various lubricants based on existing animal fats and oils, vegetable fats and oils, mineral lubricants, etc. have been researched and developed. But,
At present, it has not been possible to obtain a sufficient anti-seizure effect.

The inventors of the present invention effectively prevent seizure of a stainless steel plate on a rolling roll when using a mixed solution of powdered iron oxide and graphite dispersed in a viscous aqueous solution as a lubricant for hot rolling. It has been found that Japanese Patent Application Laid-Open No. 64-83309 and Japanese Patent Application Laid-Open No. 1-16
It was introduced in Japanese Patent No. 7396. This lubricant has a significantly better seizure prevention effect than the conventional hot rolling lubricant.

[0005]

However, even if the above-mentioned lubricant is used, surface scratches may occur in some cases. In particular, if the pass schedule is changed or the rolling temperature is changed in the hot rolling process, the load on the roll may increase beyond the action of the lubricant that suppresses the occurrence of seizure. As a result, surface scratches cannot be completely prevented. By the way, the environment in which stainless steel products are used is becoming severer year by year, and the required service life is also becoming longer. To meet these demands,
Stainless steel containing a large amount of alloy elements such as Cr and Al has begun to be used. When hot rolling a stainless steel sheet having such a composition and composition with high oxidation resistance, the amount of oxide scale produced on the surface of the steel sheet during rolling is smaller than that of conventional stainless steel. Therefore, a metal-metal touch occurs between the roll and the roll, and seizure on the roll easily occurs.

The lubricant previously proposed by the inventors of the present invention is effective in reducing the degree of seizure when used in hot rolling of such a stainless steel sheet. It cannot be completely prevented. As a result, the stainless steel sheet may become a hot rolled coil with surface scratches depending on the hot rolling cycle. The surface scratches are not limited to hot rolling, but surface scratches may also occur in other hot working methods such as hot extrusion in which a stainless steel material is extruded into a predetermined shape at a high temperature.

The present invention has been devised to solve such a problem, and by utilizing the synergistic action of iron oxide and metal peroxide dispersed in a viscous aqueous solution, fluctuations in rolling conditions can be achieved. The purpose of the present invention is to obtain a hot-working product that does not have surface scratches by exhibiting a sufficient seizure-preventing action even when the material to be rolled or the material to be rolled is changed.

[0008]

In order to achieve the object, the lubricant for hot working of stainless steel according to the present invention is 1-30.
It is characterized in that iron oxide of 1% by weight and metal peroxide of 1 to 30% by weight are dispersed in a viscous aqueous solution in a total dispersion amount of 2 to 30% by weight. It is preferable that 90% by weight or more of each of iron oxide and metal peroxide be fine powder having a particle size of 10 μm or less. The viscous aqueous solution is prepared by dissolving a polymeric thickener in water, preferably 10 to 500.
It has a poise viscosity.

[0009]

[Operation] The phenomenon in which the material to be rolled sticks to the hot working roll is considered to be caused by the following mechanism, taking hot rolling as an example. Stainless steel plate
It is plastically deformed by pressing with a rolling roll, and a new surface is revealed. The nascent surface is derived from the base metal that is not covered with oxide scale and has an active surface state. When the nascent surface comes into direct contact with the metal surface of the rolling roll, mutual metal atoms cause thermal diffusion and pseudo-attach at the contact interface in a high temperature state.

The inventors of the present invention have considered that pseudo-attachment is suppressed when a substance that prevents mutual diffusion of metal atoms is present on the contact surface of the metal-metal touch between the stainless steel plate and the rolling roll. The iron oxide contained in the lubricant is
It intervenes in the contact surface between the stainless steel plate and the rolling roll in the roll bite, and exhibits a releasing action that suppresses pseudo attachment. As a result, seizure of the stainless steel plate on the rolling roll is prevented.

On the other hand, the metal peroxide contained in the lubricant is
It is a metastable substance containing excess oxygen. Therefore, metal peroxides tend to release excess oxygen under certain conditions to become more stable oxides. The oxygen released from the metal peroxide oxidizes the surrounding substances,
Prevents the contact interface between the stainless steel plate and the rolling roll from becoming a metal-metal touch.

For example, when heating a metal peroxide in contact with steel, oxygen is released from the metal peroxide according to the reaction of the following equation. The released oxygen oxidizes the elements in the steel and forms an oxide on the surface of the steel. MnO ₂ + Fe → MnO + FeO 3 MnO ₂ + 2Cr → 3MnO + Cr ₂ O ₃ CuO ₂ + Fe → CuO + FeO

When the metal peroxide serving as an oxygen supply source is supplied as one component of the lubricant into the roll bite at the time of rolling in a high temperature state, at least a part of the metal peroxide causes the above reaction, Oxide scale is generated on the surface of stainless steel plate and rolling roll. As a result, the oxide scale present at the contact interface prevents the mutual diffusion of the metal elements and suppresses the occurrence of seizure.

The lubricant of the present invention contains iron oxide as a substance that suppresses pseudo-adhesion by intervening at the contact interface between the stainless steel plate and the rolling roll, and further forms oxide scale on the surface of the stainless steel plate and the rolling roll. It contains a metal peroxide as a promoting substance. The iron oxide and the metal peroxide have a synergistic effect in preventing the occurrence of seizure, and efficiently cover the new surface generated by the plastic deformation that progresses in the roll bite. Further, as compared with the lubricant containing only iron oxide, a higher releasing effect can be obtained. It is presumed that this is partly due to the fact that the metal peroxide that did not contribute to the oxidation reaction is directly present at the contact interface between the stainless steel plate and the rolling roll.

Iron oxide and metal peroxide are prepared into a viscous aqueous solution and supplied to a rolling roll. The compounding ratio of iron oxide and metal peroxide to the viscous aqueous solution is restricted in terms of seizure prevention effect, supply method and the like. If the mixing ratio of iron oxide and metal peroxide is too small, the surface of the rolling roll and the stainless steel plate cannot be sufficiently covered, and the oxygen released by the reaction oxidizes the surface of the rolling roll and the stainless steel plate. The action becomes insufficient. As a result, the anti-seizure effect is reduced. In order to obtain a given effect with a lubricant containing a small proportion of iron oxide and metal peroxide, it is necessary to increase the absolute amount of lubricant supplied, and the lubricant should be used in a state suitable for actual operation. Supply becomes difficult.

If the mixing ratio of the iron oxide and the metal peroxide is too large, not only the anti-seizure effect will be saturated and the excess iron oxide and the metal peroxide will be wasted, but also the viscous aqueous solution will not be consumed. Dispersive mixing becomes difficult. For example, in a viscous aqueous solution containing a large amount of iron oxide and metal peroxide, suspended iron oxide and metal peroxide easily settle, and the properties of the lubricant change when left standing for a long time. . Further, the piping system for supplying the lubricant to the surface of the rolling roll is apt to be clogged and the operation becomes unstable. From such a thing,
The amounts of iron oxide and metal peroxide dispersed in the viscous aqueous solution must be 1 to 30% by weight, respectively. Also,
Even the total dispersion amount is set within the range of 2 to 30% by weight.

Iron oxide is composed of FeO, Fe ₃ O ₄ , and Fe ₂ O.
_In the present invention, any iron oxide and a mixture thereof can be used although it takes the form of ₃ or the like. Also, as the metal peroxide, although the kind thereof is not particularly limited, it is preferable to use manganese dioxide, copper dioxide or the like from an industrial viewpoint. Furthermore, it is also possible to use a metal peroxide as a composite oxide, which is a kind of compound combined with iron oxide. Iron oxides and metal peroxides not only make it difficult to effectively coat the surfaces of rolling rolls and stainless steel plates with too large a particle size, but also tend to settle in the state of being mixed with a viscous aqueous solution, resulting in a homogeneous dispersion. It becomes difficult to maintain the condition. In particular, finer metal peroxide has a larger reaction area, and facilitates surface oxidation of the rolling roll and the stainless steel plate. In this respect, the particle size of iron oxide and metal peroxide is preferably 90% by weight or more, and fine particles of 10 μm or less.

The viscosity of the viscous aqueous solution is important for maintaining the mixed iron oxide and metal peroxide in a homogeneous dispersion state. If the viscosity is too low, suspended iron oxides and metal peroxides tend to settle, the characteristics of the stored lubricant fluctuate, and troubles such as blockage occur in the piping system that supplies the lubricant. However, if the viscosity is too high, it is necessary to set a very high discharge pressure when supplying the lubricant to the peripheral surface of the rolling roll, and the lubricant suitable for the mounting industry cannot be supplied. Therefore, by adding a polymeric thickener, 1
The viscosity of the viscous aqueous solution is adjusted within the range of 0 to 500 poise. As long as the viscous aqueous solution satisfies the conditions regarding viscosity,
The type is not particularly limited. The viscosity of a viscous aqueous solution can be easily adjusted by adding a trace amount of a thickener. As the thickener, various polymer thickeners such as acrylic acid polymers are used.

[0019]

【Example】

Example 1: C: 0.006% by weight, Si: 0.15% by weight, Mn:
0.23% by weight, P: 0.024% by weight, S: 0.00
From ferritic stainless steel containing 1% by weight, Ni: 0.16% by weight, Cr: 18.23% by weight, Mo: 1.03% by weight, Ti: 0.41% by weight and Al: 0.23% by weight. , Plate thickness 25 mm, width 40 mm and length 200 mm
The test piece for hot rolling was cut out.

The hot rolling conditions were one pass rolling with a rolling temperature of 900 ° C. and a rolling reduction of 75%. The rolling roll has a diameter of 350 mm and a body length of 30 made of hot work tool steel SKD61.
A 0 mm roll was used. Further, the test piece which is the material to be rolled was heated to 950 ° C. in an inert gas atmosphere in order to suppress the generation of scale. The scale formed on the surface of the test piece after heating was thin with a film thickness of about 1 μm or less.

Prior to hot rolling, a lubricant was sprayed on the surface of the rolling roll as shown in FIG. That is, the pressure of the lubricant contained in the lubricant container 1 is 100 kgf.
/ Cm ² pump is used to send to the injection nozzle 3 via the supply conduit 2 and from the injection nozzle 3 as fine lubricant droplets 4 to 20 r.p.m. p. m. It was jetted onto the circumferential surface of the rolling roll 5 rotating at. At this time, the injection width was set to 200 mm and the injection time was set to 3 seconds.

A total weight of 5 g of lubricant was supplied to the peripheral surface of the rolling roll 5. This supply amount corresponds to forming a liquid film having a film thickness of about 20 μm on the peripheral surface of the rolling roll 5.
After the lubricant is sprayed on the peripheral surface of the rolling roll 5, the water contained in the high-pressure water container 6 is pressured from the nozzle 7 to 3 kgf / c.
It was jetted as a water drop 8 at m ² . This supply of water corresponds to the supply of roll cooling water, and if the viscosity of the lubricant is appropriate, the rate of runoff is reduced, and the rate of adhesion of the lubricant to the rolling rolls 5 is increased.

As the lubricant, as shown in Table 1, a viscous aqueous solution containing an acrylic acid polymer as a thickener was used.
As the manganese dioxide dispersed in the viscous aqueous solution, a fine powder having an average particle diameter of 0.8 μm and a proportion of powder having a particle diameter of 10 μm or less of 98% by weight was used. As the copper oxide, a fine powder having an average particle diameter of 2.5 μm and 94% by weight of powder having a particle diameter of 10 μm or less was used. For iron oxide,
The average particle size is 1.2 μm, and there are 9 powders with a particle size of 10 μm or less.
A fine powder was used which accounted for 9% by weight.

[0024]

[Table 1]

Hot rolling was performed under the condition that a lubricant film was formed on the surface of the rolling roll 5 by spraying each lubricant, and after rolling, the surface of the rolling roll 5 and the test piece were observed to check whether seizure occurred. investigated. As is clear from Table 1 showing the results of the investigation, iron oxide and manganese dioxide were used alone, respectively.
In the examples using the lubricant dispersed in an amount of -30% by weight and 2-30% by weight in total, hot-rolled sheet having no surface seizure and good surface properties was observed. Had been rolled into. In addition, the supply amount, the attachment amount, and the attachment rate in Table 1 are values calculated based on iron oxide and metal peroxide.

Example 2 The effects of the viscosity of the viscous aqueous solution, the dispersion amount of iron oxide and metal peroxide, the particle size, etc. on the stability of fine particle dispersion in the prepared lubricant were investigated. Iron oxide and metal peroxide were mixed with the viscous aqueous solution to prepare a lubricant, which was then placed in a beaker and allowed to stand. Then, the dispersion state of the iron oxide and the metal peroxide after one week was investigated. As the investigation method, a method was adopted in which a lubricant sample was taken from the upper part of the beaker, the contents of iron oxide and metal peroxide contained in the sample solution were measured, and the contents were compared with the contents at the initial stage of preparation. The survey results are shown in Table 2.

[0027]

[Table 2]

As is clear from Table 2, when most of the particle diameters of iron oxide and metal peroxide are 10 μm or less, the total dispersion amount is 30% by weight or less, and the viscosity of the viscous aqueous solution is 10 poise or more, The sample liquid collected from the upper layer of the beaker after standing for a week contained iron oxide and metal peroxide in almost the same contents as the lubricant at the initial stage of preparation. This indicates that the lubricant prepared according to the present invention maintains a stable fine particle dispersion state without causing fine particle sedimentation. Therefore, the lubricant can be supplied to the circumferential surface of the rolling roll 5 under stable conditions for a long period of time without causing the supply conduit 2, the injection nozzle 3 and the like to be blocked. In addition, in the above-mentioned Examples, an example in which the lubricant of the present invention was used for hot rolling of stainless steel was described. However, the lubricant of the present invention is not restricted to this, and is similarly applied to other hot working methods such as hot extrusion of a stainless steel material into a predetermined shape.

[0029]

As described above, the lubricant of the present invention effectively prevents roll seizure during hot working of stainless steel, and a high-quality product without surface scratches can be obtained.
In addition, damage to the processing rolls is reduced, and the unit consumption of rolls is also reduced. Since the manufactured hot-worked product has a clean surface, surface polishing can be reduced or omitted, and it is possible to manufacture stainless steel materials with high productivity and high added value such as mirror finishing applications. .

[Brief description of drawings]

[Fig. 1] Mechanism for spraying lubricant to rolling rolls

[Explanation of symbols]

1 Lubricant Container 2 Supply Conduit 3 Injection Nozzle 4 Lubricant Droplet 5 Rolling Roll 6 High Pressure Water Container 7 Cooling Water Nozzle 8 Water Droplet

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location C10M 103: 06) A 9159-4H C10N 10:02 10:14 10:16 20:06 Z 8217- 4H 30:02 30:06 40:24 Z 8217-4H

Claims (3)

[Claims] 1. A stainless steel heat comprising 1 to 30% by weight of iron oxide and 1 to 30% by weight of a metal peroxide dispersed in a viscous aqueous solution in a total dispersion amount of 2 to 30% by weight. Lubricant for hot working. 2. A lubricant for hot working of stainless steel, wherein 90% by weight or more of each of the iron oxide and the metal peroxide according to claim 1 is a fine powder having a particle size of 10 μm or less. 3. The lubricant for hot working of stainless steel, wherein the viscous aqueous solution according to claim 1 is adjusted to have a viscosity of 10 to 500 poise by adding a polymer thickener.