JPH05171165A - Lubricant for hot rolling of seamless metal pipe - Google Patents

Abstract

PURPOSE:To provide a lubricant not causing the generation of inner surface flaws due to the adhesion of the lubricant to the inner surface of the metal pipe, having excellent lubricity, and free from danger of carburization. CONSTITUTION:10 Pts.wt. of a particulate oxide lamellar compound is mixed with 5-10 pts.wt. of a binder, which comprises the mixture of one or two of boron oxide and boric acid with an alkali metal borate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubricant for hot rolling, which is mainly used for producing a seamless metal tube by a Mannesmann tube manufacturing method.

[0002]

2. Description of the Related Art As is well known in the manufacture of seamless metal pipes by the Mannesmann pipe manufacturing method, a heated solid billet or bloom is made into a hollow pipe by a punching machine, and then the hollow pipe is stretch-rolled. Finished into a product tube by. As stretch rolling mills, erogator, assel mill, plug mill,
A mandrel mill or the like is used, and drawing rolling with a plug mill is usually combined with tube rolling with a reeler.

In the drawing and rolling process of the Mannesmann pipe manufacturing method,
The inner surface of the pipe is forcibly lubricated with a lubricant to prevent seizure. As the lubricant, a graphite-based lubricant mainly composed of granular graphite, scaly graphite, earth-like graphite, etc. is often used in the state of a solid or a liquid mixed with a binder. When the graphite-based lubricant is used, there is no problem in lubrication performance even when the material to be rolled is a difficult-to-process material such as stainless steel or high alloy. However, in these materials, their corrosion resistance is impaired by carburization.

That is, when the inner surface of the tube is lubricated with a graphite-based lubricant in the stretching rolling of stainless steel or high alloy, the carburization of the inner surface of the tube causes the selective corrosion of the grain boundary due to the grain boundary precipitation of chromium carbide and its vicinity. The corrosion resistance deteriorates and the product performance is impaired.

In order to solve this problem, a binder 1 comprising 10 parts by weight of powdered oxide-based layered compound typified by mica and one or more of boron oxide, boric acid and an alkali metal borate is used. A non-graphite type lubricant for hot working consisting of 5 to 5 parts by weight has been proposed by JP-A-64-16894.

[0006]

The oxide-based layered compound represented by mica exhibits excellent performance as a main lubricant. Therefore, the proposed lubricant may be highly evaluated in the investigation of the coefficient of friction by the ring compression test. However, the oxide-based layered compound does not oxidize and wear like graphite when it is kept at a high temperature. Therefore, in an actual rolling experiment with a plug mill and reeler, the lubricant in the solid state during plug mill rolling adhered to the tool surface and the inner surface of the rolled material, causing medium-strength flaws on the inner surface of the pipe and causing the remaining lubrication on the inner surface of the rolled material. It was found that the agent caused flaws on the tool surface in the reeler rolling in the next step, and as a result, also generated continuous pit flaws in a spiral shape on the inner surface of the pipe.

Further, in an actual rolling experiment of a mandrel mill, the lubricant used in the former stage of the mill adhered to the bar surface and the inner surface of the rolled material in the latter stage of the mill to cause a medium flaw on the inner surface of the pipe.

It is an object of the present invention to provide a lubricant for hot rolling of seamless metal pipes which is non-carburizing and excellent in lubricity and which does not have a risk of inducing streaks on the inner surface of the product.

[0009]

An oxide type layered compound represented by mica functions as a non-carburizing lubricant base agent having excellent lubricity. The present inventor has disclosed in Japanese Patent Application Laid-Open No. 64-64, for the purpose of suppressing scratches on the inner surface of a product without impairing its function.
The lubricant disclosed in 16894 was reviewed. As a result, the binder in the lubricant strongly influences the induction of muscle defects, and increasing the amount of the binder is effective in suppressing muscle defects, and the lubricant contains boron oxide, boric acid and an alkali metal borate having an equivalent bond. Considered as an agent, it can be used alone, but in reality, the function as a binder is different between boric acid-based and alkali metal borate-based, and it is effective to suppress streaks by mixing both, I found out.

The present invention has been made on the basis of the above findings, and is a bond formed by mixing 10 parts by weight of a particulate oxide-based layered compound with one or two of boron oxide and boric acid and an alkali metal borate. More than 5 parts by weight of the agent and 10 parts by weight or less,
The gist is a lubricant for hot rolling of seamless metal tubes, which is characterized by comprising

[0011]

The lubricant for hot rolling of the seamless metal pipe of the present invention is
The amount of the binder is more than 5 parts by weight and 10 parts by weight or less with respect to 10 parts by weight of the lubricant main agent composed of the oxide-based layered compound, and
By making the binder a mixture of one or two of boron oxide and boric acid and an alkali metal borate,
Despite being non-carbon type, it shows excellent lubricity, and
Can prevent streaks on the inner surface of the product.

The lubricant of the present invention is particularly effective for the lubrication of the inner surface of the pipe in the stretching / rolling process and the polishing / rolling process in producing a seamless metal pipe by the Mannesmann pipe manufacturing method.

As the seamless metal pipe, carbonaceous lubricants are selected from austenite type, ferrite type, two-phase type and martensite type, which have a relatively low carbon content (C: 0.1% or less), which may cause internal carburization. Each stainless steel and Ni-based (Ni: 5
Metal tubes made of high alloys of 0% or more) and Cr-based (Cr: 50% or more) can be mentioned as particularly effective targets.

Used as a main lubricant in the lubricant of the present invention
Oxide-based layered compounds are, for example, natural or artificial mimetics.
It is a mosquito. As mica, potassium tetrasilicon mica {K
Mg_2.5(Si_FourO_Ten) F₂}, Sodium tetrasilicon
Mosquito {NaMg_2.5(Si_FourO _Ten) F₂}, Natural gold mica
{KMg₃(AlSi₂1O_Ten) (OH)₂} Etc.
One or more of these can be used. Also,
Vermulais instead of or with mica
Tonto, bentonite, etc. can also be used.

The particle size of the main lubricant is preferably 2 to 20 μm for use.

The binder adheres the lubricant main agent as a binder to the friction surfaces of the tool and the workpiece during rolling, and prevents the inner surface flaw from being caused by the residual lubricant main agent after rolling. Therefore, the binder is boric acid (such as H ₂ BO _3, HBO ₂₎ and with one or two boron oxide (B ₂ O _3), a mixture of alkali metal borates, and the lubricating base resin 10 weight The mixing amount with respect to parts is more than 5 parts by weight and 10 parts by weight or less.

Here, since boric acid releases moisture at 270 ° C. or higher and decomposes into boron oxide, either boric acid or boron oxide may be used in hot rolling, or a mixture thereof may be used as a binder. The function does not change. Boric acid and boron oxide form slag at high temperature and act as a liquid lubricant to reduce wear resistance, but rather have strong performance as a binder and prevent adhesion of the main lubricant to the tool surface and material surface. Facilitate. On the other hand, the alkali metal borate does not have a lubricating action as much as that of boric acid, and the action of preventing the adhesion of the lubricating main agent has priority over the performance as a binder at high temperatures.
Therefore, the harmful effect of the boric acid-based binder is suppressed by using this alkali metal boric acid.

When the amount of the binder is 5 parts by weight or less with respect to 10 parts by weight of the lubricating main agent, the lubricant does not fit into the tool or the rolled material, resulting in poor lubricity. Internal defects due to the agent occur. When it exceeds 10 parts by weight, the ratio of the main lubricant is reduced, resulting in deterioration of lubricity. Among the lubricants disclosed in Japanese Patent Laid-Open No. 64-16894, a binder having 10 parts by weight is mentioned as an example of insufficient lubricity. This is because the binder is composed of an alkali metal borate alone. This is because When the ratio of alkali metal borate in the binder is small, there is a concern that defects may occur due to the remaining lubricant, and when it is large, there is a risk of insufficient lubrication due to a decrease in the relative amount of boric acid binder. The amount of alkali metal borate is 15% based on 100% by weight of the binder.
~ 50% is desirable.

Alkali metal borates include lithium borate, sodium borate and potassium borate, and, like borax (Na ₂ B ₄ O ₇ .10H ₂ O), metaborate or pyroborate and / or hydrate. Things can also be used.

The particle size of the binder is preferably 2 to 20 μm for use.

[0021]

EXAMPLES Examples of the present invention will be described below.

First, the results of the lubricant application test on the Mannesmann-Plug mill line will be described.

A hollow tube having an outer diameter of 280 mm × a wall thickness of 12 mm × a length of 8 m obtained by piercing and rolling an SUS304 material with a piercer and then rolling it with an elongator is 275 mm in outer diameter × 10 mm in wall thickness by a plug mill while lubricating the inner surface. × Stretched and rolled to a length of 9.7 m, further subjected to tube rolling on the inner and outer surfaces with a reeler, and then fixed with a sizer to an outer diameter of 273.1 mm × a wall thickness of 10 mm. The rolling finish temperature by the plug mill was about 1000 ° C. on the outer surface of the rolled material.

The inner surface lubrication is performed only by a plug mill, and in order to uniformly supply the lubricant, the lubricant in the hopper is jetted from the core metal between the guide plug and the work plug by compressed air, and rolling slide is performed by the work plug. The method of continuously supplying to the moving part during rolling was adopted. Tables 1 and 2 show the relationship between the composition of the lubricant and the performance. The average particle size of the lubricant is 10 μm, and the supply amount is about 1
It was 50 g / book.

The performance of the lubricant is the lubricity of the plug mill. The depth of the inner surface of the product is 0.2 mm or more. The presence or absence of medium-strength flaws and the life of the plug, and the remaining state of the lubricant, the presence of reeler plug flaws on the inner surface of the product. Was evaluated. The evaluation criteria are no medium flaws, no reeler plug flaws, good plug life of 5 passes or more (○), no middle flaw, no reeler plug flaws, usable level of 4 or less plug life (△), medium flaw or reeler The case where the plug flaw was generated was judged to be unusable (x), and particularly, the case where the number of the middle flaws was 5 or more was evaluated as poor (xx). The plug life is the number of rollings until it is determined that seizure or damage on the surface of the plug will cause harmful defects to the product.

In No. 1, since the lubricant did not contain a binder and was only mica as the main lubricant, the lubricant did not fit on the tool and the rolling agent, and many flaws occurred. Regarding Nos. 2 to 6, since the binder contained no alkali metal borate, the lubricity of the plug mill was excellent, but the reeler caused plug defects due to the adhesion of the residual lubricant plug. No. 7-1
Regarding No. 1, since the binder does not contain boric acid and only the alkali metal borate is used, the lubricity in the plug mill is poor. No. 1
In Nos. 2 to 14, 18, 19, 31, and 32, the binder is a mixture of boric acid and an alkali metal borate, but the absolute amount is small, so that the lubricity is insufficient, and the mica after rolling is a reeler plug. Moved to and a plug defect occurred. No.
Regarding 17, 22, 23, 27, 29, 30, 37, 38, the ratio of the binder in the lubricant was too high, and the lubricity was deteriorated due to insufficient mica.

In contrast to these, No. 20, 24 to 2 of this method
In Nos. 6, 33, 35 and 36, the lubricity in the plug mill is good, and there is no plug flaw due to the remaining mica, and the tool life is long. Nos. 15, 16, 21, and 34 are also this method, but the amount of boric acid in the binder is small, so that the lubricity decreases and the tool life is relatively short. No. 28 is also this method, but since the amount of alkali metal borate in the binder is small, boric acid does not melt and adhere to the plug surface of the plug mill, and no flaws occur, but the tool life is relatively short.

[0028]

[Table 1]

[0029]

[Table 2]

Next, the results of the lubricant application test on the Mannesmann-mandrel mill line will be described.

Outer diameter 181 mm × wall thickness 16 mm × length obtained by rolling SUS304 material with a piercer and shell sizer
A 6.5 m hollow tube was stretch-rolled by a 7-stand mandrel mill to an outer diameter of 151 mm x wall thickness of 5 mm x length of 23.5 m, and then soaked in a reheating furnace and an outer diameter of 114.3 mm with a reducer. X The diameter was fixed up to 5 mm. The mandrel mill finishing temperature was about 900 ° C.

For internal lubrication, 100 g of lubricant powder was made into an aqueous solution of 5 liters using an alcohol-based solvent (concentration of about 1%), and was applied off-line to the surface of the mandrel bar to a thickness of about 60 μm, and then at room temperature. After leaving it to stand in the atmosphere for about 10 hours to dry it, the mandrel bar was inserted into the tube. It has been confirmed that about 1% of the organic solvent used in the lubricant aqueous solution does not leave a harmful carburized structure or the like on the inner surface of the SUS304 tube after the solution treatment. Table 3 shows the relationship between the composition of the lubricant and the performance.

The lubricant has a depth of 0.
The presence or absence of medium streaks (bar streaks) of 1 mm or more and the rolling stability were evaluated. The evaluation criteria are that there is no flaw and the apparent bar friction coefficient (bar retainer load / total rolling load) is 0.07.
Good (○) when stable rolling less than 0, usable level when there is no flaw but unstable product rolling with bar friction coefficient of 0.070 or more and uneven product thickness (△), bar friction Unusable when one or more defects occur regardless of the coefficient (×),
The case where the lubricity was extremely poor and the bar friction coefficient was estimated to be 0.15 or more, and the mandrel mill rolling itself was impossible due to the intermediate clogging of the rolled material was rated as poor (xx).

[0034]

[Table 3]

In No. 1, since no binder was used, the adhesion of the lubricant to the bar was poor and rolling was impossible.
In No. 2, since the alkali metal borate was not contained in the binder, the lubricating main agent adhered to the bar, causing flaws. In No. 3, since the binder was only the alkali metal borate, the lubricity was inferior and the borax-induced scratches were induced. No. 4, 8, 1
In No. 7, due to the lack of binder, the main lubricant was fixed and remained on the bar, causing flaws. On the other hand, in Nos. 7, 12, 13, and 18, rolling was unstable and flaws were caused due to lack of the main lubricant.

In contrast to these, No. 6, 9, 10,
In Nos. 14 to 16, the lubricity was good, the amount of the main lubricating agent remained was small, and no flaws occurred. No. 5 is also this method, but since the amount of alkali metal borate is large and the amount of boric acid is small, the bar friction coefficient is high and rolling is slightly unstable. However, no defects occurred. No. 11 also uses this method, but since there is little alkali metal borate, boric acid melts and adheres to the bar surface, lowering the lubricity in the latter half of rolling and increasing the friction coefficient, making rolling a little unstable. .. However, no defects occurred.

[0037]

As is apparent from the above description, the lubricant for hot rolling of seamless metal pipes of the present invention is a non-carbon type lubricant which has no risk of carburization, but has good lubricity and There is no risk of internal flaws due to the remaining adhered lubricant.

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location C10M 103: 00 A 7419-4H 103: 06 E 7419-4H) A 7419-4H C10N 30:06 40:24 Z 8217-4H 50:08

Claims (1)

[Claims] 1. A binder formed by mixing 10 parts by weight of a particulate oxide-based layered compound with one or two kinds of boron oxide and boric acid and an alkali metal borate and more than 5 parts by weight and 10 parts by weight or less. A lubricant for hot rolling of seamless metal tubes, which comprises: