JPH0826342B2 - Lubricant for mandrel mill - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a lubricant for hot metal working, and in particular, in the production of seamless steel pipe in a mandrel mill, a new bar or heat treatment is carried out by regrinding during use. In the case where pipes are manufactured using a bar from which the scale is removed, the lubricating performance is satisfactory for the initial pipe manufacturing work, which was conventionally difficult.

[Prior Art] Material of bar used in mandrel mill, heat treatment,
Various patents have been filed for surface treatment and surface roughness, but for domestic mandrel mills, for example, 5Cr
The material that is hardened and tempered is often used. The problem here is that when the heat treatment scale on the surface of the mandrel mill is removed in the final step, or when re-polishing occurs when seizure, rough skin, dimensional defects, etc. occur during use. When used in a so-called machined state such as when used in a state, seizure is apt to occur.

When rolling the surface of a mandrel bar with a metal surface like a new bar, conventionally, after bar processing, about 10 to 40 wt% graphite, about 5 to 30 wt% synthetic resin, about 1 to 5 wt% dispersant, about 25 to about 25 water. 85w
Approximately 50 to 1 on the bar surface using a graphite lubricant consisting of t%
Apply so that the amount of adhesion is about 00g / m ^2, and after sufficiently drying (1
It is used more than day and night. Therefore, under the present circumstances, increasing the amount of the lubricant adhered prevents bar seizure due to the lubricant running out in the latter half of rolling.

[Problems to be Solved by the Invention]

If a cutting bar coated with a conventional type of lubricant is used, (i) Lubrication is liable to occur in the latter half of rolling, and if it occurs, seizure may occur because the iron base is exposed. , (Ii) At the same time, the restraining force (tension in the rolling direction of the mandrel bar) becomes high and the burst ripping from the shell deteriorates. At that time, the chatter vibration of the bar becomes large, the load on the equipment becomes large, and the equipment may be damaged. Some things are raised as problems.

The cause of these is that, as the lubrication is cut off, the iron base material comes out as described above, so it is impossible to expect the lubrication effect of the iron oxide film layer, which is generally said, and the base material comes out, and seizure occurs. It can be easier.

Therefore, if rolling is repeated several times, the scale layer is gradually formed by the heat and oxygen received from the material, and it becomes difficult to seize.In such a state, the difficulty is generally reduced, but a satisfactory normal It has a drawback that it takes time to start driving.

The present invention has been made in view of such circumstances,
When the heat treatment scale on the surface of the mandrel mill is removed or when it is re-polished,
It is an object of the present invention to provide a lubricant for hot metal working, which does not cause seizure due to lack of lubrication and exerts sufficient lubricating performance for pipe manufacturing work.

[Means for solving the problem]

The present inventors, as a result of earnest study from such a viewpoint,
There is no contamination in the work environment by blending graphite with a specific compound, and not only expecting the lubricating effect of the graphite-based lubricant by simply applying it to a new bar or re-polishing bar, but also exposing the iron substrate. The inventors have completed the present invention by finding that a dense and strong iron oxide film can be formed on the formed surface.

That is, the gist of the present invention is, in a lubricant for hot metal working, comprising graphite and a synthetic polymer, graphite 20 to 55 wt.
%, Synthetic polymer 15-65 wt% and organic carboxylic acid 10-
A lubricant for a mandrel mill, which is characterized by comprising 30 wt% and having a pH of 4.0 or less.

The graphite used in the present invention may be a natural product or a synthetic product as long as it is a powder, and it is preferable that the particle size is about 100 μ or less and the purity is at least about 80% or more. Those with 50μ and a purity of about 90% or more are preferably used. Examples of the synthetic polymer used in the present invention include vinyl acetate, ethylene-vinyl acetate and other vinyl ester polymers and copolymers, acrylic acid or its ester polymers and copolymers, styrene and ethylene. Polymers or copolymers of the above, unsaturated dicarboxylic acid polymers or copolymers, and the like can be used.

As the organic carboxylic acid used in the present invention,
When the lubricant of the present invention is dispersed in water, the following compounds capable of maintaining an acidic region, preferably pH 4 or less, can be used.

By containing a certain amount of such an organic carboxylic acid, it can be made acidic when dispersed in water, and an oxide film can be easily formed on the iron surface.

Further, the lubricant of the present invention includes a conventional water-soluble dispersant, for example, carboxymethyl cellulose (CMC), polysaccharides, natural or synthetic polysaccharides such as guar gum, polyvinyl alcohol, polyoxyethylene alkyl ether,
It is also possible to add and use a synthetic dispersant such as sulfonate or a compound generally called an antiseptic, a rust preventive or an antifoaming agent.

The preferred blending ratio of each of the three components of graphite, synthetic polymer and organic carboxylic acid is about 20 wt% or more for graphite, about 15 wt% or more for synthetic polymer, and about 5 wt% or more for organic carboxylic acid, and particularly preferable. About 30 to 55 wt% graphite
%, Synthetic polymer about 15-65 wt%, organic carboxylic acid about 10-
It is in the range of 30 wt%.

Here, if the blending amount of graphite is too small, a problem occurs in the original lubricity, and if the blending amount of the synthetic polymer is too small, the film-forming property becomes difficult, and uniform lubricity cannot be obtained, and the organic carboxylic acid is not obtained. If the compounding amount of is too small, an effective iron oxide film cannot be obtained.

The amount of the lubricant of the present invention dispersed in water is about 10
If the amount is too much, the viscosity becomes high and the handling becomes difficult. If the amount is too small, the adhesion to the bar becomes poor and the lubricity is poor.

〔The invention's effect〕

The effects of the hot metal working lubricant according to the present invention are summarized as follows.

1) An iron oxide film, which can be expected to have a lubricating effect, is formed by using the lubricant of the present invention in the state where the heat treatment scale on the surface of the mandrel mill is removed or the state where it is re-polished.

2) By maintaining lubricity in the initial rolling stage and preventing seizure, burst ripping from the shell can be improved and equipment load can be suppressed.

3) By preventing seizure, it is possible to improve the pipe forming property and product quality, reduce the rolling loss time for exchanging the seizure bar, and improve the productivity.

Next, Examples and Comparative Examples of the present invention are shown in Tables 1 and 2, but the present invention is not limited thereto.

〔Example〕

Hereinafter, the content of the present invention will be described more specifically based on Examples.

Examples of specific components and comparative examples are shown in Table-1 and Table-2, but as a usage method, a brush or a brush is used to apply about 50 to 100 g / m ² to the exposed surface layer of the iron base material. If left as it is for about one day and night, it will be about 2 for the lubricant shown in the example.
An oxide film layer of .mu.-4 .mu. is formed. The mill scale layer formed by ordinary rolling has a thickness of about 20 μm, which is thin, but exhibits an excellent seizure resistance in the first few layers. Even when compared with the restraining force, the one coated with the lubricant of the present invention has a restraining force which is almost similar to the accustomed bar from the first one, whereas the conventional lubricant has a restraining force of about 20. You can see that it is 30% higher.

That is, with the lubricant shown in the comparative example, even if the coating amount is increased, an effective oxide film layer is not formed, so that good lubricity cannot be obtained. Table 3 shows the results of restraining power, pipe forming property and product quality. The work material is
STH (high carbon steel) inner diameter 232mm, wall thickness 5.
A mandrel mill with a bar diameter of 231 mm was used so that the length was 5 mm and the length was 26 m.

The restrain force is a torque value converted from the current value of the drive motor, and an example of the restrain force diagram is shown in FIG.

[Brief description of drawings]

FIG. 1 is an example of a restrain force diagram during pipe making work in a mandrel mill, where the vertical axis is restrain force and the horizontal axis is time. In the figure, (1) is the maximum restraining force, (2) is the step of penetrating the mandrel through the work piece, and (3) is the step of stripping the mandrel from the work piece.

Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location C10M 129: 32 129: 34 129: 36) C10N 30:10 40:24 Z 50:02 (56) References Kai 58-49800 (JP, A) JP 58-138795 (JP, A) JP 62-250099 (JP, A)

Claims (1)

[Claims] 1. A lubricant for hot metalworking comprising graphite and a synthetic polymer, wherein the graphite is 20 to 55 wt% and the synthetic polymer is a polymer.
Consisting of 15-65 wt% and organic carboxylic acid 10-30 wt%,
A lubricant for a mandrel mill, which has a pH of 4.0 or less.