JP2518231B2 - How to prevent seizure during hot working of steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is generated on a work material or the surface of the tool due to friction between the work material and a tool such as a roll or a die during hot plastic working of the steel material. The present invention relates to a method for preventing seizure flaws.

(Prior art) In hot plastic working of materials such as stainless steel, which has excellent resistance to oxidation at high temperatures, the surface of the material and processing tools such as rolls and dies, or skids and guides that come into contact when the material is conveyed. Alternatively, friction with a rail or the like may cause seizure, which may cause significant damage to the surface.

As means for preventing this seizure, measures such as supplying various lubricants and using tools made of a material that is unlikely to cause seizure are taken.

(Problems to be solved by the invention) However, in the temperature range around 1200 ° C such as plastic working of steel materials, lubrication is caused due to the fact that the lubricant burns or the lubricant is hard to adhere. It is difficult to supply the agent. Even if a sufficient amount of lubricant can be supplied, there is a problem in that, for example, during rolling, slipping occurs between the rolls and a biting failure occurs.

In addition, the method of using tools which hardly cause seizure still does not provide sufficiently satisfactory results. For example, although ceramic tools are being used in recent years, ceramic tools have a problem that cracking and damage are often caused by lack of impact resistance and they are extremely expensive.

The present invention has been made in view of such problems,
It is an object of the present invention to provide a method in which seizure does not occur even though ordinary tools made of heat-resistant steel are used, and moreover, slip does not occur during rolling or the like.

(Means for Solving Problems) The present inventors have found that materials such as stainless steel having excellent oxidation resistance at high temperatures cause seizure when these materials are heated or processed at high temperature. Focusing on the fact that metal-to-metal contact is likely to occur due to the small amount of oxide film that is generated, when processing such a material that is prone to seizure, a function to prevent seizure on the material surface in advance is provided. Consideration was given to applying a substance having a thickness to form a film effective in preventing seizure.

However, as described above, it is difficult to apply such a substance to the surface of a material having a high temperature. Therefore, the present inventor applies a substance effective for seizure prevention to the surface of the material before heating, and then heats the material. Therefore, a seizure-resistant film with good adhesion was not constructed.

Then, as a result of various experiments and researches conducted by the present inventor for forming a seizure-resistant film, powders of metal oxides such as iron oxide were mixed at an appropriate ratio with water glass as a binder to obtain an appropriate thickness. The inventors have found that it is preferable to heat after coating, and have established the present invention.

That is, the present invention, during hot plastic working of the steel material, a paint composed of iron oxide powder and water glass mixed in a weight ratio within the range of 1: 1 to 2: 1, 100-1000 μm This is a method for preventing seizure during hot working of a steel material, which is characterized in that the material is applied in a thickness and then heated to perform hot plastic working.

In the present invention, the powder means a powder having a diameter of 50 μm or less.

The following Table 1 shows the results of investigation of the presence or absence of seizure and the coefficient of friction from the results at 1200 ° C. by the high temperature friction test method shown in the attached drawings. In the attached drawings, 1 is a cylindrical test piece corresponding to a workpiece, 2 is a test piece corresponding to a tool, 3 is a high-frequency coil for heating the cylindrical test piece 1, and 4 is also a cylindrical test piece. 1 shows the anti-seizure agent applied.

Table 1 shows the results when the anti-seizure agent was applied to a thickness of 100 μm, x indicates that baking occurred, and o indicates that it did not occur. If the coefficient of friction is less than 0.2, slippage is likely to occur during rolling, so the evaluation was evaluated as x.

As is clear from Table 1 above, ferric oxide (Fe ₃ O ₄ )
Has a slightly smaller coefficient of friction than ferric oxide (Fe ₂ O ₃ ), but both have good seizure resistance and have a ratio with water glass.
Within the range of 1: 1 to 2: 1, there is no harm in promoting slip. However, if the ratio with water glass is 0.5: 1, the coefficient of friction becomes too low and slip may occur. Further, when the ratio of water glass is 3: 1, both coatings are easily peeled off, and seizure occurs.

Further, Table 1 also shows a case where aluminum oxide (Al ₂ O ₃ ) and calcium oxide (CaO) are used as a comparative example. As is clear from the table, aluminum oxide (Al ₂ O ₃ ) In terms of seizure prevention, the particles have a similar effect, but are not desirable from the viewpoint of tool friction due to the hard particles, and calcium oxide (CaO) tends to have a low friction coefficient, which may cause slippage. The proper mixing range with is narrowed.

In the method of the present invention, the desirable range of the coating thickness of the coating material was confirmed by the experiments and studies by the present inventor, and the results are shown in Table 2 below. Table 2 shows the results of the same test conducted by changing the coating thickness by the same test method as in Table 1 above.

As is clear from Table 2 above, the coating thickness is 50 and 1500.
In the case of μm, seizure has occurred. This is because when the thickness is 50 μm, the coating thickness is too thin and scale is generated through this coating film, and the coating film peels off together with this scale. If it is 1500 μm, the coating film is too thick and the coating film peels off integrally. Therefore, based on these results, the coating thickness in the method of the present invention was set within the range of 100 to 1000 μm.

(Operation) The present invention, when the hot plastic working of the steel material, the coating material formed by mixing iron oxide powder and water glass in the range of 1: 1 to 2: 1 by weight ratio, 100 ~ Since it is applied to a thickness of 1000 μm and then heated to perform hot plastic working, by directly forming an iron oxide layer with good adhesion on the steel material, direct contact between metals is reduced and seizure is prevented. it can.

(Examples) 1) When hot rolling a steel sheet, apply a paint of 1: 1 Fe ₃ O ₄ : water glass to a thickness of about 200 μm on the surface of a slab of SUS304 stainless steel before heating, and apply 1250 It was heated to ℃, and then hot rolling was performed at a rolling reduction of 35%.

When hot rolling was carried out by the usual method under the same conditions, significant seizure flaws were generated in the vicinity of the edges of the steel sheet, whereas in the case of the method of the present invention, seizure was not generated at all.

In order to prevent seizure, when a normal resin hot rolling fat was used, rolling could not be satisfactorily performed due to slip.

2) When piercing and rolling with a seamless steel pipe piercing and rolling machine, the SUS304 stainless steel billet surface before heating
Fe ₂ O ₃ : Water glass 1: 1 paint was applied to a thickness of about 200 μm, heated to 1290 ℃, and then pierced and rolled at a piercing ratio of 2.0. Spiral seizure flaws were generated on the outer surface by friction with the guide shoes, whereas seizure was not generated at all by the method of the present invention.

In addition, when the coating material of Fe ₂ O ₃ : water glass of 0.5: 1 was applied, slipping occurred and it was not possible to perforate. Also Fe ₂ O ₃ :
When the water glass was applied with a paint of 3: 1, the coating film peeled off and seizure defects occurred.

(Effect of the invention) As described above, the present invention, during the hot plastic working of the steel material, the coating material formed by mixing the iron oxide powder and water glass in the range of 1: 1 to 2: 1 by weight ratio, 100-1000μ on the surface of the work material
Since it is applied after heating to a thickness of m to perform hot plastic working, by applying an iron oxide layer with good adhesion to the steel material in advance, direct contact between metals is reduced and seizure is prevented. it can. Therefore, according to the present invention, great results can be obtained in extending the tool life, improving the quality of the product, reducing the number of maintenance steps, and the like.

[Brief description of drawings]

 The drawing is a schematic illustration of a high temperature friction test method. 1, 2 is a test piece, 3 is a high frequency coil, 4 is an anti-seizure agent.

Claims (1)

(57) [Claims] 1. A paint comprising a mixture of iron oxide powder and water glass in a weight ratio of 1: 1 to 2: 1 at the time of hot plastic working of a steel material, is applied to the surface of the work material in an amount of 100 to 1000 μm. A method for preventing seizure during hot working of a steel material, which comprises applying a thickness and then heating to perform hot plastic working.