JPH03259998A - Lubricant for hot working of metal - Google Patents

Abstract

PURPOSE:To provide a lubricant for hot working of metal, which has excellent lubricity and scarcely causes carburization by mixing graphite with the ammonium salts or 4-8C alkylamine salts of molybdic acid and boric acid. CONSTITUTION:Component (A) comprising an ammonium slat or 4-8C alkylamine salt of molybdic acid is mixed with component (B) comprising an ammonium salt or 4-8C alkylamine salt of boric acid (e.g. diethylamine salt of boric acid) and graphite (C) to give a lubricant for hot working of metal. It is suitable that the weight ration of A to B be about (20:80) to (80:20) and the weight ratio of (A+B) to C be about (20:80) to (80:20). When the obtained lubricant is used for a Mannesmann mandrel mill, components A and B form a homogeneous aqueous solution, serving to disperse graphite stably and to spread it evenly.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention is a method for hot processing alloy steel such as stainless steel (alloy of iron with elements such as manganese, chromium, nickel, and molybdenum) as a seamless steel pipe. It relates to lubricants for hot metal processing used when processing metals, and more specifically, to prevent the carburization phenomenon that occurs when processing with conventional lubricants containing organic systems with low thermal decomposition. It is a lubricant that is difficult to carburize.

(Prior Art) Conventionally, various lubricants used in seamless steel pipe processing of carbon steel, particularly Mannesmann mandrel mill steel pipe processing, have been used as lubricants for seamless steel pipe processing of alloy steel. These lubricants are made from combinations of mineral oil + graphite, asphalt + graphite, and organic polymer compound dried graphite, and these compositions contain organic substances with low thermal decomposition that thermally decompose at about 500 U or less. Contains.

Among these compositions, in addition to graphite, boric acid, borax, glass, salt, boron nitride, molybdenum disulfide,
Inorganic substances such as phosphoric acid are used alone or in a mixture of two or more types, but these lubricants have poor lubricity as lubricants for mandrel mills, and in reality, they are not used other than as supplementary additions to graphite. is not used.

(Problems to be Solved by the Invention) When the above-mentioned lubricant for processing seamless carbon steel pipes is used as a lubricant for processing seamless pipes of alloy steel such as stainless steel, the following carburizing problems occur: Intergranular corrosion is likely to occur.

For example, in stainless steel, chromium carbide generally precipitates at the grain boundaries due to thermal history, which is effective in improving corrosion resistance, but a sensitization phenomenon that deteriorates intergranular corrosion resistance may occur due to a relative decrease in chromium.

The limit to the occurrence of sensitization is determined by the amount of carbon in the steel and its thermal history, but in general, as the amount of carbon increases, sensitization increases.

Even if the thermal history is likely to cause sensitization, carburization can be achieved by processing with a lubricant containing organic substances, for example.
When the amount of carbon in the steel increases locally, sensitization occurs in the portion where the amount of carbon increases, which may deteriorate intergranular corrosion resistance.

Therefore, it is important to prevent carburization by lubricants when processing stainless steel in order to ensure intergranular corrosion resistance.

(Means for Solving the Problems) In order to completely eliminate carburizing properties in processing alloy steel, it is necessary to remove organic substances (including graphite) from the lubricant components. Therefore, the present inventors conducted various studies on these lubricants, but they were not successful due to poor lubricity.

However, according to the results of these studies, we have obtained the useful knowledge that the components that cause carburization in stainless steel processing using a mantledge mill are hydrocarbon components that thermally decompose and gasify under about 5 oocu at normal pressure, and that the degree of carburization is highest and that of graphite is the lowest. Ta.

Therefore, as a result of further intensive studies, the inventors of the present invention found that when ammonium salts of molybdic acid and boric acid, or certain alkylamine salts and graphite are used as essential components dispersed in water, Mannesmann mandrel The present inventors have discovered that when alloy steel is processed by a mill, the carburization property is low, that is, the intergranular corrosion resistance is excellent, and the present invention has been completed. That is, the present invention contains an ammonium salt of molybdic acid or an alkylamine salt having a total of 4 to 8 carbon atoms, an ammonium salt of boric acid or an alkylamine salt having a total of 4 to 8 carbon atoms, and graphite. A lubricant for hot metal working characterized by the following.

The present invention will be explained in detail below.

The lubricant for hot metal working of the present invention is applied by spraying or other methods to a mandrel bar during rolling. It is subjected to rolling in this state.

The reason for using ammonium salts or alkylamine salts having a total carbon number of 4 to 8 in terms of their composition is that these acid salts are water-soluble from the viewpoint of dispersibility, and that they are not mixed with water after being applied to the mandrel bar. Organic matter evaporates and about 500c during rolling.
It is intended that there be no organic matter that thermally decomposes at temperatures below.

The alkylamine salt has a total carbon ta of 4 to 6 in the alkyl group.
Diethylamine (boiling point approx. ss, 9r)
), triethylamine (boiling point: 89.4C), n-butylamine (boiling point: about 77.Oc'), etc. can be used. If the total carbon number is too small, the boiling point will be too low and it will evaporate at room temperature, so it cannot be used in practice. If the total carbon number is too large, it will not evaporate after being coated with a mandrel bar. Molybdic acid and boric acid generally have a purity higher than that used for chemical or industrial purposes.

In the present invention, the ammonium molybdate ring or the above alkyl amine salt and the ammonium borate salt or the above alkyl amine salt are essential, and since one alone cannot be effective, the blending ratio of the two should be approximately 0 parts vs. 90
It can be used in a range of 0 parts to 10 parts, preferably from 0 parts to 80 parts to 0 parts to 20 parts, more preferably from 0 parts to 70 parts to about 10 parts. If either is too much or too little (0 parts vs. 30 parts), the lubricity will be poor.

Next, the graphite used in the present invention is preferably one obtained by pulverizing commonly used natural or artificial graphite by ordinary means and having good dispersibility in water.

The lubricant of the present invention is used in the hot working of alloy steel in the form of dispersion in water. Based on the total amount of the ammonium ring of molybdic acid, boric acid or the above alkylamine salt, about 20 to 80 wt, preferably about 30 to 75 wt.
t ratio, graphite about 20-80 wt%, good iL< about 25-7
I am in charge of 0wt.

Too much graphite causes problems in adhesion to the mandrel and also increases carburization. Too little graphite causes problems in terms of lubricity. The blending amount of the lubricant of the present invention to be dispersed in water is about 10 to 70 wt%, preferably -1t, and < is about 25 to about 55 wt%. If it is too high, storage stability and adhesion to the bar will deteriorate, resulting in poor lubricity.

In the present invention, a small amount of a general dispersant may be added to aid in the dispersion of graphite, and it is also possible to add a small amount of an antifoaming agent, a rust preventive, etc. As dispersants, starch etc. and its derivatives,
Examples include amylose triacetate and its derivatives, dextrin triacetate and its derivatives, carboxymethyl cellulose and its derivatives, polysaccharides such as polysaccharide, gums such as guar gum, etc., and about 0.1 wt% to 3.0 wt%. Owt
Can be used within a range of %.

Antifoaming agents include silicone oils such as dimethyl silicone and methylphenyl silicone, which are approximately 0.001w.
t%~1. It can be used within the range of owt%.

Rust inhibitors include sulfonic acids, carboxylic acid salts, morpholine, amines such as alkylamines, benzotriazole, thiazole, etc., and their content ranges from 0.01 wt% to 3 wt%.
Can be used within the range.

(Effects of the Invention) The main effects of the present invention as a lubricant for Mannesmann mandrel mills are summarized as follows.

1) Boric acid and molybdic acid are homogenized in an aqueous solution state as an ammonium salt or an amine salt, stably disperse graphite, and spread uniformly on the bar.

2) After spreading on the bar, the ammonium and amine salts fly off with water and form a homogeneous water-insoluble film on the bar in the absence of organic matter.

3) Carburization phenomenon is minimal in processing alloy steel pipes.

4) Good lubricity.

(Examples) Next, Examples and Comparative Examples of the invention are shown in Table 1, but the present invention is not necessarily limited thereto.

Examples 1 to 4, Comparative Examples 1 to 3 Compositions of Examples and Comparative Examples of the lubricant of the present invention are shown in Table 1.

Using the lubricant shown in Table 1, rolling was carried out in a restraint type 5-stand mandrel mill in which the mandrel bar speed can be controlled. The raw pipe is 89.1 wxgx8. of the two steel types shown in Table 2. Using Oa+ thick hollow tube,
At the exit side of the mandrel mill, 74.01111g x 5. Om
+ Thick finished pipe.

Table 2 Composition of rolled material (wt%) The mandrel bar surface was kept at about 120C and the lubricant shown in 1-1 Table 1 was sprayed with a spray nozzle at about 50 to 60 I/□'
It was applied to a uniform thickness and subjected to rolling.

By controlling the mandrel bar speed to be slower than the material speed on the exit side of the M1 stand and rolling, the thrust force pb acting on the mandrel bar and the total rolling load ΣPi of M1 to 5 stands are measured, and the mandrel bar and the rolled material are measured. Thrust coefficient b μ S corresponding to the average coefficient of friction between the material and the material: 2×ΣP! According to the findings of the present inventors in calculating , it has been found that the thrust coefficient increases when the lubricating performance of the lubricant is poor. usually,
If the thrust coefficient is about 0.08 or less, rolling can be carried out successfully without any problem in lubrication performance, but as it becomes larger than 0.08, defects on the inner and outer surfaces of the rolled material tend to occur frequently due to poor lubrication performance. . Furthermore, if it exceeds 0.35, the mandrel bar and the material to be rolled become stuck, the rolling load increases rapidly, and eventually rolling becomes impossible.

A test piece was taken from the inner surface of the finished pipe after rolling, and JIS
After 650CX2hr sensitization heat treatment as specified in G 0575, immersion in boiling sulfuric acid-sulfuric acid solution for 16 hours and bending test were performed to observe cracks due to intergranular corrosion on the inner surface, and to determine the presence or absence of carburization. was evaluated.

The rolling and corrosion test results are shown in Table 3.

In test A-F using the lubricant of Example 1.2.3.4, which is an example of the present invention, the thrust coefficient was 0.07 or less, and rolling was good, and the corrosion test results showed no cracking. Not confirmed and carburization is not recognized.

On the other hand, in tests G and H when the lubricant of Comparative Example 1 containing synthetic resin as a binder was used, the thrust coefficient was 0.05 and the rolling was good, but the corrosion test showed that the thrust coefficient was due to intergranular corrosion. Cracks have occurred, and carburization is observed. Furthermore, when using the lubricant of Comparative Example 2.3 containing sodium silicate and sodium phosphate as an inorganic binder, no cracking was observed in the corrosion test in Test) NIII, J, but the thrust coefficient during rolling was is 0.28.0.
It is high at 35 or more, and defects on both internal and external surfaces occur frequently. In particular, in Tess) I'&J, rolling became impossible due to the sudden increase in load during rolling.

Claims (1)

[Claims] Ammonium salt of molybdic acid or total carbon number 4
A lubricant for hot metal working, characterized in that it contains an alkylamine salt having a carbon number of 1 to 8, an ammonium salt of boric acid or an alkylamine salt having a total carbon number of 4 to 8, and graphite.