JPH04331292A - Lubricant for hot tube rolling and method for preventing seizure flaw of hot rolled tube - Google Patents

Abstract

PURPOSE:To improve the effect of preventing seizure flaw by incorporating a metal oxide powder with a specified particle size and sodium silicate in water. CONSTITUTION:A lubricant for hot tube rolling with a viscosity of 200-5,000cp is obtained by dissolving or dispersing 10-60wt.% of a metal oxide powder with a particle size of 2mm or less and 2wt.% or less of a dispersant and/or thickener in an aqueous solution containing 10-50wt.% of sodium silicate as solid. A material 1 to be rolled is passed through a first drill 2 after it has been heated and coated on its outer surface with the lubricant at the inlet A of the drill 2. The resultant material 1 is further coated with the lubricant on its outer surface in the section B between the drill 2 and a second drill 3 and then passed through the drill 3 to conduct skew drilling and rolling.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubricant used in hot tube rolling such as inclined perforation rolling in Mannesmann tube manufacturing, and a method for preventing seizure defects in hot rolled tubes using the lubricant.

0002

2. Description of the Related Art In an inclined rolling mill used for manufacturing seamless steel pipes, guide shoes are used to prevent the outer diameter of a material to be rolled which is perforated and rolled by inclined rolls from expanding more than necessary. As this guide shoe, a plate type one or a disc roll type one is used, but no matter which type of guide shoe is used, the material to be rolled comes into sliding contact with the guide shoe as it rotates, so during this time It is necessary to use a lubricant to prevent seizure.

[0003] As the lubricant used in inclined piercing rolling, there is a metal oxide-based liquid lubricant. As a method of using the lubricant, a method of supplying a lubricant between a material to be rolled and a guide shoe is disclosed in Japanese Patent Application Laid-Open No. 63-234092. Further, Japanese Patent Application Laid-Open No. 184410/1984 discloses a method of applying a lubricant to the outer surface of a material to be rolled before rolling the material. When comparing the two, the former has the problem of being prone to seizure defects due to uneven lubrication, and the latter method of applying lubricant before rolling, disclosed in JP-A-60-184410, is better. , which is superior in terms of uniform lubrication over the entire surface.

0004

[Problem to be solved by the invention] However,
The method of applying a lubricant to the rolled material before heating, which is shown as Method A in Publication No. 184410, is effective as a countermeasure against seizure defects for the first punching machine, but it is It is insufficient to prevent seizure defects in rolling mills. This is because the lubricant applied to the rolled material before heating hardly peels off even when heated or transported after heating.
Although it contributes to rolling with the perforator, by the time the rolling with the first perforator has finished, the amount of residual lubricant has significantly decreased, and the remaining lubricant is also used during material transfer up to the second perforator. This is because most of the scale falls off along with the scale that occurs.

[0005] To solve this problem, Japanese Patent Application Laid-Open No. 60-1844
As shown in Method B in Japanese Patent No. 10, a lubricant may be applied to the heated rolled material immediately before being supplied to the first punching machine and the second punching machine. However, the lubricant used here is EH Coat (trade name of Aiko Co., Ltd.) with water added. When water is added to the EH coat, its viscosity will vary depending on the amount of water added, but in normal use
It drops to below 00cp. When a lubricant whose viscosity has been reduced by adding water in this way is applied to a hot rolled material after heating, the water contained in the lubricant becomes explosively vaporized, causing the lubricant to splatter. The adhesion efficiency of the lubricant is significantly reduced, making it impossible to completely prevent the occurrence of seizure flaws. Furthermore, when applied to xizers and reducers where the rolled material is at a relatively low temperature, water evaporation becomes insufficient and adhesion deteriorates, making it impossible to obtain a sufficient lubricating effect.

[0006] An object of the present invention is to provide a lubricant for hot tube rolling which has an excellent effect of preventing seizure defects and a method for preventing seizure defects.

[0007]

[Means for Solving the Problems] The lubricant of the present invention contains metal oxide powder with a particle size of 2 mm or less: 10 to 60% by weight, sodium silicate as solid content: 10 to 50% by weight,
Furthermore, if necessary, it is an aqueous solution containing at least 2% by weight of a dispersant and a thickener, and has a viscosity of 20%.
It is characterized by being 0 to 5000 cp.

[0008] The method for preventing seizure defects of the present invention is characterized in that the lubricant is applied and adhered to the outer surface of the material to be rolled at the entrance side of the rolling mill, and then the material to be rolled is passed through the rolling mill. .

[0009]

[Operation] The lubricant of the present invention is used by being applied directly to the surface of the material to be rolled. The step of adhesion may be before or after heating the material to be rolled. In the case of heating, for example, in a Mannesmann pipe production line, the material to be rolled passes through rolling mills such as the first perforator, second perforator, mandrel mill, plug mill, Assel mill, Zizer, reducer, etc. Apply on the side. The lubricated material to be rolled immediately enters the rolling mill. The timing of coating is 1 to 6 before rolling.
0 seconds before is appropriate. The coating can be similarly applied to reducers and the like in a forge-welded pipe production line.

The lubricant of the present invention contains a suitable amount of water due to its limited viscosity range. Therefore, even when applied to heated rolled material before rolling, the water will not explode into steam and the metal oxide powder will not fly off, and the adhesion efficiency is good. Adhesion does not deteriorate even when the heating temperature is relatively low. Therefore,
A sufficient amount of adhesion is ensured by applying it to the heated rolled material before rolling.

The main component of the lubricant of the present invention that adheres to the surface of the heated material to be rolled is usually sintered and fixed to the surface of the material to be rolled at temperatures of 500° C. or higher. If the material to be rolled does not reach this temperature, auxiliary heating may be performed on the material to be rolled. Further, when the temperature of the rolled material is sufficiently high, the scale adheres to the surface of the rolled material by melting or forming a solid solution through a eutectic reaction or eutectoid reaction. However, if the lubricant contains metal oxides other than iron oxide (such as silicic acid), a temperature of 1140°C or higher is required in order for this to adhere to the iron oxide on the surface of the rolled material through a eutectic reaction. Therefore, it is desirable to use such a lubricant when the temperature of the rolled material on the entry side of the rolled material is maintained at 1140° C. or higher.

[0012] The metal oxide powder used in the lubricant of the present invention includes alumina (Al2O3) and silica (S
iO2 silicic acid), iron oxide (Fe2 O3 or Fe3
O4), chromium oxide (Cr2O3), and the like. The reason why the powder particle size is set to 2 mm or less is to prevent the occurrence of avatar defects and to enable spray application using existing commercially available nozzles. Regarding the content, 10% by weight
If it is less than 60% by weight, seizure will occur, and if it exceeds 60% by weight, the dispersion stability of the metal oxide powder will be impaired and the spray coating operation will become difficult due to gelation (increased viscosity). Therefore 10～
The content was 60% by weight.

Sodium silicate as a solid component is a binder for adhering the metal oxide powder to the material to be rolled. An aqueous solution of sodium silicate is called water glass. The lubricant of the present invention is also a mixture of water glass and metal oxide powder and the like. The content of this sodium silicate is 10
~50% by weight is because if it is less than 10% by weight, it will not function as a binder and the necessary adhesion will not be obtained.
This is because if it exceeds % by weight, it will gel (increase in viscosity) and make spray coating difficult.

Dispersants are specifically anionic types such as naphthalene sulfonic acid soda formalin condensate, soda salt of styrene/maleic anhydride copolymer resin, polyacrylic acid sodium salt, polyethylene glycol alkyl ether, polyethylene glycol alkyl It is a nonionic type such as phenyl ether, etc., and is added as appropriate to improve the dispersion stability of the metal oxide powder in the water glass solution and to facilitate the spraying operation. However, since the effect is saturated even if added in a large amount, the upper limit is set at 2% by weight.

[0015] The thickener is specifically an organic substance such as carboxymethyl cellulose, hydroxyethyl cellulose, sanzan gum, etc., and is appropriately added to finely adjust the viscosity. However, since adding a large amount will reduce the binder function of sodium silicate, the upper limit is set at 2% by weight.

In the lubricant of the present invention, its viscosity is determined by the viscosity of the water glass used and the amount of water added thereto, and the viscosity of the water glass is determined by the amount of water contained in the water glass. Therefore, increasing the viscosity means decreasing the amount of water contained in the lubricant, and decreasing the viscosity means increasing the amount of water contained in the lubricant. If the viscosity is less than 200 cp, when the lubricant is applied to the heated and high-temperature rolled material, the water in the lubricant will explosively vaporize and the lubricant will scatter, causing the lubricant to spill onto the surface of the rolled material. Not fully adhered. In the case of rollers, reducers, etc. in which the rolled material is kept at a relatively low temperature, the drying of the lubricant is insufficient, resulting in insufficient adhesion. If the viscosity exceeds 5,000 cp, it will gel (increase in viscosity) and become impossible to spray and apply. Therefore, the viscosity is 200 to 5000 cp, which corresponds to approximately 30 to 70% by weight in terms of water content.

In the method for preventing seizure defects of the present invention, the above-mentioned lubricant is applied to the outer surface of a rolled material to be subjected to rolling at the entrance side of the rolling mill. FIG. 1 shows an embodiment in which the method of the present invention is applied to piercing and rolling in a Mannesmann pipe production line.

After the material 1 to be rolled is heated, it is passed through the first punching machine 2.
, the second punching machine 3 in turn. The lubricant is applied to the entrance side A of the first drilling machine 2 and the space B between the first drilling machine 2 and the second drilling machine 3.
Both are applied to the surface of the material to be rolled 1 by spraying. If lubricant is applied only on the entry side of the first drilling machine 2, the second
Lubrication during piercing rolling is insufficient because the amount of lubricant remaining on the surface of the rolled material 1 rolled by the first piercing machine 2 is small, and the lubrication during rolling by the second piercing machine 3 is insufficient. It becomes impossible to sufficiently prevent the occurrence of seizure defects. On the other hand, if the lubricant is applied only between the first piercing and rolling mill 2 and the second piercing and rolling mill 3, the lubrication will naturally not occur in the first piercing and rolling. Therefore,
Lubrication in the first drilling machine 2 is performed on the entry side of the first drilling machine 2, and lubrication in the second drilling machine 3 is performed on the entry side of the second drilling machine 3.

[0019]

[Examples] Examples of the present invention will be described below.

[0020] When manufacturing duplex stainless steel pipe (22Cr-6Ni-3Mo steel, product outer diameter 273.1 mm x wall thickness 10 mm x length 12 m) on the Mannesmann plug mill line, the entrance side of the first drilling machine ( Approximately 500 from a roll
Various lubricants were applied by airless spraying from a distance of about 500 mm to the surface of rolled materials (30 pieces each), which were billets prepared by heating to 1290° C. and then descaling. Tables 1 and 2 show the results of investigating the composition of the applied lubricant and the seizure properties during the first piercing rolling. The surface temperature of the rolled material at the coating position is 1160 to 1200.
It was ℃. Further, the time from application to first piercing rolling was about 10 seconds. All of the examples of the present invention can be spray coated, the applied lubricant does not scatter, has excellent adhesion, and can suppress the occurrence of seizure flaws.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

Effects of the Invention The lubricant for hot tube rolling of the present invention can be applied by spraying, and moreover, it can be applied directly to a heated material to be rolled to ensure a sufficient amount of adhesion. Therefore, it can be applied to the material immediately before rolling on the entry side of the rolling mill, and unnecessary drop-off due to transfer etc. is also prevented. Therefore, seizure defects are significantly suppressed.

[0024] The method for preventing seizure defects of the present invention allows a sufficient amount of lubricant to adhere to the rolling mill at the entrance side of the rolling mill, thereby exhibiting an excellent seizure effect.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the method of the present invention.

[Explanation of symbols]

1 Rolling machine 2 First piercing rolling mill 3 Second piercing rolling mill

Claims (3)

[Claims] [Claim 1] Metal oxide powder with a particle size of 2 mm or less:
10-60% by weight, sodium silicate as solids:
It consists of an aqueous solution containing 10 to 50% by weight and has a viscosity of 2.
A lubricant for hot tube rolling, characterized in that it has a lubricant of 00 to 5000 cp. 2. The hot tube rolling lubricant according to claim 1, further comprising at least 2% by weight of one or more of a dispersant and a thickener. 3. Hot rolling characterized in that the lubricant according to claim 1 or 2 is applied and adhered to the outer surface of the material to be rolled at the entrance side of the rolling mill, and then the material to be rolled is passed through the rolling mill. Method for preventing seizure defects on pipes.