JPH0336608B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for warm forging iron-based materials, which has excellent seizure resistance and can perform warm forging quickly and safely.

[Prior art]

Warm forging is a method of forging in a temperature range between cold forging and hot forging, and generally refers to forging at 600 to 900°C for steel materials. In this temperature range, steel has lower deformation resistance than when cold, and there is less risk of the material cracking during forging. In addition, since the processing temperature is lower than that of hot processing, there is less occurrence of oxidized scale and less decarburization.

However, the problem with warm forging is that the friction conditions between the die and the workpiece (billet) are severe, so the punch is particularly susceptible to seizure, and the die is susceptible to softening and wear. There are many things.

Therefore, graphite-based lubricants have been mainly used for a long time. However, in this case, as shown in the comparative example, when drilling a deep cup from the rear as shown in Figure 1, the punch seizes, making it impossible to perform good forging, and the work environment due to the use of graphite bad.

A method has also been proposed in which boron oxide (B ₂ O ₃ ), a low-melting point metal oxide, is used as a lubricant and is applied to the billet prior to warm forging (Japanese Patent Application Laid-Open No. 1983-1996). 210338). This method is
Compared to the above-mentioned graphite-based lubricants, it exhibits excellent seizure resistance even in deep cup backward drilling. However, in this case, B ₂ O ₃ powder is mixed with water,
Dispersed in a solvent such as alcohol, and then added with CMC (carboxyl methyl cellulose) and PVA as binders.
(polyvinyl alcohol), etc. is added to make a slurry, and this is applied. Therefore, when water is used as a solvent, it takes time to dry after application, and when alcohol is used, there is a risk of ignition. Therefore, there is a problem in applying it to a warm forging line in a factory.

We also use _B2O3 powder and heat it _at high temperature (600~
B ₂ O ₃
Another method is to melt the powder and apply it. This method allows coating to be performed in a short time. However, as shown in FIG. 6, which will be described later, the higher the forging temperature, the more seizure occurs. This is caused by the reaction between the oxidized scale of the billet and B ₂ O ₃ that occurs at high temperatures.
This is thought to be due to a decrease in lubrication performance.

[Problems to be solved]

In view of the problems of the prior art described above, the present invention has been made to:
An object of the present invention is to provide a warm forging method for iron-based materials that exhibits even better anti-seizure properties and can quickly and safely perform warm forging while also taking advantage of the advantages of the conventional technology using B ₂ O ₃ . It is something.

[Means for solving problems]

The present invention involves applying a pretreatment agent containing boric acid as a main component to the surface of a billet made of iron-based material, heating the billet, and applying a lubricant containing boron oxide as a main component to the billet surface. A method for warm forging iron-based materials characterized by warm forging.

In the present invention, as the pretreatment agent containing boric acid (H ₃ BO ₃ ) as a main component, H ₃ BO ₃ or a combination thereof with a binder such as CMC or PVA is used. Further, when applying the pretreatment agent to the surface of the billet, the pretreatment agent is mixed with water to form a slurry, and the mixture is applied by dipping, brushing, spraying, or the like. The amount of H ₃ BO ₃ in the pretreatment agent to be applied is preferably 10 to 60 g ^per square meter of billet surface. If it is less than 10 g/m ² , the effect of suppressing oxidation on the billet surface will be poor when the billet is heated to the warm forging temperature, and the seizure resistance will be reduced.
The larger the amount of H ₃ BO ₃ applied, the better the oxidation suppressing effect mentioned above, but if it exceeds 60 g/m ² , the pre-coat film of the pre-treatment agent will dry out at the normal billet temperature (80-250°C) during application. This makes it difficult to heat the coating, and the coating is likely to foam or peel when heated to a high temperature for warm forging. Further, the above coating is preferably carried out at 250° C. or lower in order to prevent damage such as cracking to the coating. Furthermore, the application of the pretreatment agent dries the pretreatment agent on the billet to form a precoat film.

Next, the billet is heated to 580 to 800°C after application of the pretreatment agent and drying. This heating is for applying the lubricant described below.

The lubricant applied to the billet surface after the above heating is B ₂ O ₃ or P ₂ O ₅ (phosphorus pentoxide),
Na ₂ O (sodium oxide), K ₂ O (potassium oxide)
etc. are added. The powder of this lubricant is then applied to the billet surface by spraying or showering. At this time, the temperature of the billet is preferably 600 to 800°C. 60℃
If it is lower than , the melting point of B ₂ O ₃ (577℃) is around or below, so even if the B ₂ O ₃ powder comes into contact with the billet, it will not melt immediately and will not stick, making it impossible to quickly apply the lubricant. It's for a reason. Furthermore, if the temperature is higher than 800°C, it becomes difficult for the above-mentioned H ₃ BO ₃ to sufficiently suppress oxidation of the billet surface, making it difficult for B ₂ O ₃ to exhibit the lubricating performance during warm forging (see Figure 5). reference).

Also, the amount of B ₂ O ₃ applied is 1 m ² of the billet surface.
Preferably at least 20g per serving. If the amount is less than this, between application and forging,
This is because there is a risk of oxidation of the billet and alteration of the B ₂ O ₃ layer.

Further, when the forging temperature is 700 to 800°C, warm forging can be performed immediately by applying a lubricant to the billet heated to this temperature. Also, when the lubricant is applied at 600-700°C, the billet is reheated to the forging temperature.

Warm forging temperature is preferably 700-850℃, 850℃
If the temperature is higher than that, the lubricant B ₂ O ₃ reacts with the billet steel, causing the B ₂ O ₃ layer to change in quality, resulting in a significant drop in lubrication performance.

Although there are various methods for heating the billet as described above, such as heating in an electric furnace, it is preferable to use a high frequency induction heating method. This heating method requires a short heating time and effectively prevents oxidation of the billet surface.

[Action and effect]

In the present invention, before applying lubricant at a high temperature near the forging temperature,
Since H ₃ BO ₃ is applied and the surface of the billet is covered with the pre-coated film, oxidation of the billet surface at the above-mentioned lubricant application temperature (600 to 800°C) can be suppressed. Therefore, warm forging exhibiting excellent seizure resistance can be performed.

Also, since the lubricant is applied at high temperatures,
It is quick and does not require a long drying time after applying the lubricant, unlike conventional methods. Furthermore, since no alcohol solvent slurry is used in this application as in the past, there is no danger of ignition during the process.

Furthermore, as mentioned above, in the present invention, the pretreatment agent is applied at a relatively low temperature (250°C or less), and then heating, lubricant application, and warm forging are performed. It can also be separated from the process. However, in a practical warm forging line in a factory, one billet is usually formed every few seconds, and speed is required.
Therefore, if the pretreatment agent application in the present invention is performed outside the line, and the subsequent steps such as heating are performed on the line, the above-mentioned speed and safety can be further utilized, and the product can have excellent seizure resistance. Warm forging can be performed.

〔Example〕

Example 1 Using S45C steel as a billet, a pretreatment agent and a lubricant were applied to the billet, and backward drilling was performed by the method shown in FIG.

That is, the cylindrical billet with a diameter of 30 mm and a height of 35 mm was preheated to 140°C, and 70 g of H ₃ BO ₃ was added to the billet.
The billet was immersed in a solution of pretreatment agent mixed with 0.75 g of CMC, 1 c.c. of surfactant, and 100 c.c. of water at 90°C, and a coating of 40 g of H ₃ BO ₃ per 1 m ² of billet was applied to the surface. Formed. Next, this billet is heated to 800°C using a high-frequency induction heating device, and B ₂ O ₃ is added as a lubricant.
per 1 m ² of the billet surface by spraying
40 g of B ₂ O ₃ powder was applied.

Next, as shown in FIG.
Back drilling was performed by warm forging at Kg/ ^mm2 . Here, the inner diameter of container 1 is 30 mm, and punch 2 is
The punch tip was made of SKH51 and had a diameter of 21.2 mm, a shoulder radius of 8 mm, and a land portion 21 length of 2 mm. Furthermore, the maximum drilling depth was 51 mm.

Also, for comparison, as a pretreatment agent
Do the same as above without applying H ₃ BO ₃ ,
Rear drilling was performed.

As a result, no seizure was observed in the former method of the present invention, but seizure occurred in the latter comparative method in which no pretreatment agent was applied. Further, the surface roughness in the circumferential direction of the rounded portion (arc-shaped portion) 22 of the punch 2 after the warm forging was measured, and the results are shown in FIG. The term "surface roughness" herein refers to the roughness (seizure state) of the punch surface after the warm forging in units of μm, and the larger this value is, the worse the seizure resistance is.

In addition, in the figure, A indicates the method of the present invention, and B indicates the comparative method (hereinafter, the same applies to FIGS. 3 and 4).

Example 2 A billet was immersed in a solution of a pretreatment agent consisting of 5 g of H ₃ BO ₃ , 0.25 g of CMC, 1 c.c. of surfactant, and 100 c.c. of water ^. A H ₃ BO ₃ coating was formed. Then, heat this to 600℃,
B ₂ O ₃ powder was applied at 60 g/m ² by spraying.
Thereafter, it was reheated to 800°C and warm forged. Note that conditions other than those described above are the same as in Example 1.

In addition, for comparison, warm forging was performed in the same manner as above without applying a pretreatment agent.

As a result, the former method of the present invention did not cause any burn-in, but the latter comparative method did cause burn-in.

Further, the surface roughness of the rounded portion of the punch is shown in FIG. 3 in the same manner as in FIG. 2 above.

Example 3 40 g/m ² of H ₃ BO ₃ was applied to a billet, and 80 g/m ² of B ₂ O ₃ was applied by spraying at 600°C.
Thereafter, warm forging was performed at 850°C. The conditions other than these are the same as in Example 1.

Also, for comparison, without applying H ₃ BO ₃ ,
Warm forging was performed in the same manner as above.

As a result, although warm forging was performed at a high temperature of 850°C, the method of the present invention did not cause seizure. However, the comparative method caused significant burn-in.

Further, the surface roughness of the rounded portion of the punch is shown in FIG. 4 in the same manner as in FIG. 2 above.

As is clear from Examples 1 to 3 above,
It can be seen that the method of the present invention (A in Figures 2 to 4) exhibits superior seizure resistance compared to the comparative method (B in Figures 2 to 4).

Example 4 In order to find out the relationship between the amount of H ₃ BO ₃ applied as a pre-treatment agent to the billet surface and the application temperature of B ₂ O ₃ as a lubricant at high temperature immediately before warm forging,
Rear drilling by warm forging was carried out under the same conditions as in Example 1, except that both conditions were varied.

The results are shown in FIG. 5, with the H ₃ BO ₃ coating amount (g/m ² ) plotted on the horizontal axis and the B ₂ O ₃ coating temperature (° C.) plotted on the vertical axis. In the same figure, the dotted line is the melting point of B ₂ O ₃ (577
℃), indicating that in the region Z below this, B ₂ O ₃ does not melt and cannot be applied to the billet surface.

Further, the Y region (shaded area) surrounded by the solid line 4 and the dotted line 5 showed excellent lubrication performance (excellent seizure resistance) in the warm forging. Also, solid line 4
Burn-in occurred in the upper X region.

As shown in the figure, it is used as a lubricant.
The higher the temperature at which B ₂ O ₃ is applied, the greater the amount of H ₃ BO ₃ required to be applied as a pretreatment agent. Therefore, if the application temperature of B ₂ O ₃ is 600℃, H ₃ BO ₃
It is sufficient to apply H 3 BO 3 in an amount of approximately 10 g/m ² or more, but at 800° C., approximately 40 g/m ² or more of H ₃ BO ₃ is required.

Comparative Example B ₂ O ₃ powder was applied (melted and adhered) as a lubricant to a billet heated to a high temperature without applying a pretreatment agent, and then warm forging was performed at 800°C.
The temperature of the billet when applying B ₂ O ₃ is 600, 800, 900
C., and the B ₂ O ₃ coating was carried out at various temperatures from 20 to 120 g/m ² .

Other conditions were the same as in Example 1 above.

The results are shown in Figure 6, with the horizontal axis representing the applied amount of B ₂ O ₃ (g/m ² ) and the vertical axis representing the roughness of the punch surface (μm).
were calculated and shown for each temperature. In addition, in the same figure,
A slurry-like lubricant consisting of B ₂ O ₃ , CMC, and water is applied at room temperature (approximately 20°C) and dried, and then the billet is heated to the forging temperature (800°C) to perform warm forging. Data are also shown for cases where

As can be seen from the figure, when the B ₂ O ₃ powder is applied at a temperature of 800 or 900° C., even if the applied amount is increased, significant burn-in (large punch surface roughness) occurs. In addition, even at 600℃, the amount of coating was reduced to 60℃.
If it is more than g/m ² , the punch surface roughness will be reduced to about 0.2 μm, but the burn-in will still be large.
The reason for this is thought to be that, as mentioned in the explanation of the prior art, the oxidized scale of the billet generated at high temperatures reacts with B ₂ O ₃ and deteriorates the lubricating performance.

These things are true if H ₃ BO ₃ as a pre-treatment agent is not applied in advance as in the present invention.
This indicates that the burn-in will increase.

On the other hand, in the same figure, when a slurry of B ₂ O ₃ was applied at room temperature, the roughness of the punch surface was low and almost no sticking occurred if the coating amount was 40 g/m ² or more. However, as mentioned above, this method has problems with speed and safety, such as the time required for drying after application and the need to use an alcohol solvent. Further, it requires a large amount of B ₂ O ₃ and is uneconomical.

[Brief explanation of drawings]

1 to 5 show an embodiment of the present invention, and FIG. 1 is a sectional view showing a method of pushing out a rear hole;
Figures 2, 3 and 4 show the results in Examples 1, 2 and 3, and Figure 5 shows the results in Example 4.
Diagram showing the relationship between _H3BO3 application amount and _B2O3 application _{temperature ,}
FIG. 6 is a diagram showing the results in a comparative example. 2...Punch, 21...Land _part , 22...Round part, 3...Billet, _A ... _H3BO3 coating, B... _H3BO3 not coating, Y...Excellent seizure resistance area .

Claims (1)

[Scope of Claims] 1. After applying a pretreatment agent containing boric acid as a main component to the surface of a billet made of iron-based material, heating the billet and applying a lubricant containing boron oxide as a main component to the billet surface. A warm forging method for iron-based materials, which is characterized by warm forging. 2 Application of a pretreatment agent whose main component is boric acid,
The method for warm forging of iron-based materials according to claim 1, characterized in that the forging is carried out at a temperature of 250°C or lower. 3. The warm forging method for iron-based materials according to claim 1, wherein the lubricant is applied at a temperature of 600 to 800°C. 4 Apply lubricant at 600 to 700℃,
The method for warm forging of iron-based materials according to claim 1, characterized in that the billet is then heated to 700 to 850°C and forged. 5. Claim 1, characterized in that the lubricant is applied in an amount of 20 g or more per 1 m ² of the surface of the billet.
Warm forging method for ferrous materials as described in .