JPS5825745B2 - Tetsukoseihinno Sankahimakkeiseihou - Google Patents

Description

[Detailed Description of the Invention] In order to improve the wear resistance and corrosion resistance of steel products, a steam treatment method is widely used to create a thin film of blue-black triiron tetroxide (Fe304) by treating it in steam. .

The conventional treatment method uses 300 to 400 particles as shown in Figure 1.
After preheating in steam for t hours at a preheating temperature TP of 'C,
maintained in steam at a processing temperature TH of 450-550°C;
Immediately after the holding time th at the treatment temperature had elapsed, the treated product was taken out of the furnace.

D indicates the time point at which the processed product is taken out. However, in this kind of treatment, after a film of Fe3O4 is formed, triferric oxide (F
e203) was unavoidable, making it difficult to obtain a good coated surface.

In addition, water vapor is blown into the core at a temperature of around 200°C to preheat it, then it is treated at (550±10)°C, and then the temperature is lowered to 200-300°C in a steam atmosphere before being released into the atmosphere to form Fe3O4 on the surface of the iron core. There is also a method of forming a film, but if steam is blown at around 200°C, Fe(OH)3
and Fe(OH)2 are generated, which is not preferable.

The present invention was made to solve the above-mentioned problems, and as shown in Fig. 2, first, the temperature is preheated to 300 to 400'C, then steam is introduced, and the temperature is heated to 300 to 400°C in this steam.
Maintaining the preheating temperature TP of 0°C for t9 hours (usually 1±0.
3 hours) and 450 to 550 in water vapor.
After forming a film of Fe 304 by holding at a processing temperature (TH) of 10°C (th dark time, usually 1 ± 0.3 hours), the temperature is lowered to 200-380°C in steam, and then the air outside the furnace is heated. Take it out inside.

In addition, although the amount of steam varies depending on the volume of the furnace, 1 a normal steam atmosphere is 15 to 20 vol/ of the furnace volume in a continuous furnace.
hr, in the case of a pit furnace, 8 to 12 vol/ of the furnace internal volume
It is hr.

The Fe s O4 film was heated at 450 to 550°C in water vapor.
A film that can withstand practical use can only be obtained by holding the film at a temperature of 350°C or 400°C.
0. is formed, but the thickness of the film is so thin that it cannot be put to practical use.

Moreover, if the temperature exceeds 550°C, Fe2O3 will be produced.

When heating in air to 400°C or higher to achieve a processing temperature of 450 to 550°C, Fe2O3 is generated, so 3
Preheat in steam at 00-400°C.

At this time, it is necessary to feed steam at a temperature of 300 to 400°C.

Fe(OH)3 and F are produced when water vapor is sent at temperatures below 300°C.
If the surface is covered with e(OH)2 or the like, and on the other hand, water vapor is introduced at a temperature of 400° C. or higher, Fe2O3 will be generated, which is not desirable.

Also, if it is immediately released into the air outside the furnace from a high temperature of 450-550℃, F e 20s will be generated, but at 200-380℃
If the temperature is lowered to a temperature before taking it out of the furnace, Fe2O3 will not be generated.

This method can be applied to surface treatment of various steel products such as high-speed tool steel, powder sintered products, cast iron products, structural steel products, and electrical steel sheets.

Next, an experimental example will be shown.

The sample is a silicon steel plate with a thickness of 0.5 mm.

(1) Purge was performed for 1.5 HR with steam at 35.0°C in a continuous furnace, and then the temperature was raised to 470'C, held in a steam atmosphere for 2HR, and taken out, and Fe2O3 was detected.

(2) IHR steam purging was performed at 350°C in a pit furnace, the temperature was then raised to 470°C, IHR was held in a steam atmosphere, the temperature was lowered to 80°C in a steam atmosphere, and Fe2O3 was not detected.

(3) Perform steam purging at 350°C in a pit furnace.

Thereafter, the temperature was raised to 470°C, IHR was maintained in a steam atmosphere, and when the temperature was lowered to 440°C and taken out of the furnace, Fe2O3 was detected.

(4) Steam purging was performed at 350°C in a continuous furnace, then the temperature was raised to 470°C, held in a steam atmosphere for 40 min, and the temperature was lowered to 350°C and taken out of the furnace, but no Fe2O3 was detected.

[Brief explanation of the drawing]

Figure 1 is a heat cycle diagram of the conventional treatment method. FIG. 2 is a heat cycle diagram of the present invention.

Claims (1)

[Claims] 1 1±0 at 300-400℃ in normal steam atmosphere
．． After preheating for 3 hours, heating and holding at 450 to 550°C for 1±0.3 hours to form a Fe3O4 film is then allowed to cool down to 200 to 380°C in a steam atmosphere before being taken out of the furnace. A method for forming oxide films on steel products.