JPS63310976A - Alloying method using high-density energy - Google Patents

Abstract

PURPOSE:To form an alloyed layer having uniform characteristics by reciprocating high-density energy to uniformly melt the whole alloyed layer forming region when an alloying material is arranged on the surface of a metallic substrate, high-density energy is exerted to melt both substrate and material, and the alloyed layer having excellent characteristics is formed. CONSTITUTION:The powder 2 of an alloying material such as Cr is coated on the surface of a metallic substrate 1 over the length (l) of >=10mm with the aid of polyvinyl alcohol, etc. High-density energy of a TIG arc 4, etc., is impressed from the upper part by a TIG torch 3 to simultaneously melt the substrate metal 1 and the alloying material 2, hence a melt pool 5 is formed, the TIG4 arc is then removed to quench and solidify the metals, and the surface characteristics such as wear resistance and fatigue resistance are improved. In this case, the torch 3 is repeatedly reciprocated in the surface treating range (l) to keep the whole melt pool 5 n a molten state, hence an alloy having a uniform composition is formed in the surface treatment range (l), and an alloyed layer 6 without variance in the surface characteristics such as wear resistance and fatigue resistance is formed.

Description

[Detailed Description of the Invention] Industrial Field of Application This invention is for improving the surface properties such as wear resistance and fatigue resistance of a part of the surface of a metal base material in various automobile parts and other mechanical parts. The present invention relates to a method of locally alloying a part of the surface of a metal base material using high-density calothermal energy such as a laser beam TiG arc.

BACKGROUND OF THE INVENTION Recently, in order to locally improve surface properties such as wear resistance and fatigue strength in cylinder bores, crankshafts, and cylinder head valve spaces for automobile engines, Lasaya TIG arc, Techniques have been developed to alloy a portion of the surface layer of a metal base material made of steel, cast iron, or aluminum alloy using high-density heating energy such as plasma arc or electron beam. In this alloying process, an alloying material containing the elements to be alloyed is placed on the surface of a metal base material, and high-density heating energy such as a TIG arc or a laser beam is applied from above the alloying material and the material below it. The surface layer of the metal base material on the side is simultaneously melted and mixed together (alloyed), and then the heat is diffused to the metal base material side by moving the application position of high-density heating energy or stopping the application, and rapidly cooled. The metal base material surface layer is solidified to form an alloyed layer.

By the way, when alloying a certain length region on the surface of a metal base material by such an alloying treatment method using high-density heating energy, conventionally, the application position of high-density heating energy is
One lengthwise end (starting end) of the area where the alloying material is placed
Normally, it was moved continuously in one direction from one end to the other end (terminus).

On the other hand, although it is different from alloying treatment, one method of surface improvement treatment for metal substrates using high-density heating energy is
There is a so-called remelting chilling treatment method in which high-density energy is applied to the surface of a cast iron base material to remelt the surface layer, and then the surface layer is chilled by rapid solidification. As for the technology, the present inventors have already disclosed in Japanese Patent Application No. 61-243386 (unpublished) the application position of high-density heating energy to chill the region 1: itJ, which is 10 m or more in length on the surface of cast iron. The entire molten pool is moved back and forth along the length of the area to uniformly melt the entire area, and in that state, the application of high-density heating energy is stopped to cool and solidify the entire molten pool substantially simultaneously. We are proposing a method to do so.

Problems to be Solved by the Invention As mentioned above, in the conventional alloying processing method using high-density heating energy, when alloying a region of a certain length, the application position of the high-density heating energy is adjusted to Normally, it was moved continuously in one direction from one end to the other, but when the length of the area is long, alloying is performed by repeating melting and solidification sequentially in the direction of movement of the application position of high-density heating energy. A layer is formed and becomes ↑1. That is, the eighth
As shown in the figure, an alloying material 2 is placed on the surface of a metal base material 1, and a high-density heating energy source, for example, a TIG arc torch 3 is continuously moved in the six directions of arrows in the figure to generate a TIG arc 4.
If the application position is continuously moved, as the application position moves forward, the alloying material 2 and the surface layer of the metal base material 1 below it will be melted and a new molten pool 5 will be formed. The molten metal in the molten pool (base material 1 and alloying material 2 melted and integrated) is located at the rear of the application position in the forward direction.
are successively rapidly solidified to form an alloyed layer 6.

However, in such alloy processing methods, the molten pool that is generated at any given time during the continuous transfer of high-density heating energy is limited to a portion of the area to be treated, which means that the melt pool is This means that the amount of alloying material and metal surface layer is small, and the stirring effect of high-density energy on the molten pool is not very large.For these reasons, the problem of uneven and non-uniform composition of the alloyed layer is caused. there were.

In order to solve this problem, as mentioned above, the high-density heating energy application position is continuously moved in one direction to alloy the region from one end (starting end) to the other end (terminus) in the length direction. The high-density heating energy source is moved back to the starting end, and high-density energy is applied while continuously moving the application position in one direction from the starting end to the ending end to remelt and solidify the alloyed layer. It is also considered that the same process can be repeated as many times as necessary. However, even in the remelting process in this method, the formation of a molten pool is only a part of the total area, so the -th remelting process alone has little effect on homogenizing the composition of the alloyed layer, and therefore, the remelting process is repeated many times. It is difficult to achieve a sufficiently uniform alloy composition in the alloyed layer without repeated melting, and therefore the process takes a long time and a considerable amount of energy is required to remelt the alloyed layer once it has been cooled and solidified. must be used,
There was a problem of high energy costs.

The present invention was made against the background of the above-mentioned circumstances. When performing alloying treatment on a certain length region on the surface of a metal base material using high-density heating energy, it is possible to create an alloy with a uniform composition over the entire region. The object of the present invention is to provide a method that can form a thickening layer without increasing costs or prolonging the processing time.

Means for Solving the Problems The method proposed in Japanese Patent Application No. 61-243386 mentioned above is different from the alloying treatment method targeted by this invention, and is a method for remelting and chilling cast iron. However, they have in common that they perform melting and resolidification using high-density heating energy.

Therefore, when we conducted experiments and studies to apply this proposed method to alloying processing, we found that, as in the above proposed method, the application position of high-density DO thermal energy was reciprocated over the entire length of the region to be processed. It was discovered that the composition of the alloyed layer could be easily made uniform by moving the alloy layer so that the entire region was uniformly molten, and this invention was achieved based on this discovery.

Specifically, in this invention, an alloying material containing an element to be alloyed is placed on the surface of a metal base material, and high-density heating energy is applied from above the alloying material to heat the alloying material and the layer below the alloying material. In a method of forming an alloyed layer on the surface of the metal substrate by melting and integrating the surface layer of the metal substrate and then rapidly solidifying the surface layer, the alloyed layer is formed in an area of 10 m or more in length on the surface of the metal substrate. Alternatively, the application position of the high-density heating energy may be reciprocated in the longitudinal direction of the region over almost the entire length to uniformly melt the entire region, and then the high-density heating energy is applied in that state. This is characterized in that the application of is stopped and the entire molten pool is cooled and solidified.

Function: In the alloy processing method of the present invention, high-density heating energy such as TIG arc or laser beam is applied from above the alloying material to a region having a length of 10# or more where the alloying material is placed on the surface of the metal base material. When applying the voltage, the application position is repeatedly moved back and forth over the entire length of the region. The application of high-density heating energy melts the alloying material and the surface layer of the metal substrate underneath, and the two are alloyed, but as described above, the application position of high-density heating energy is adjusted to the area to be treated. By repeatedly moving back and forth over the entire length of the area, solidification is substantially not initiated during the application of high-density heating energy to the area, resulting in a uniform molten state over the entire length of the area. In this way, a uniform molten state is achieved over the entire length of the area to be treated, and the molten metal in the molten pool is stirred by the reciprocating movement of the application position of high-density heating energy. The alloy composition is made uniform over the entire length of the area to be treated. When the application of high-density heating energy is then stopped, the molten pool spanning the entire length of the area to be treated is rapidly cooled and solidified by thermal diffusion toward the base metal, thereby forming an alloyed layer with a uniform alloy composition. Ru.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1 to 3 show an example of a situation in which the alloying treatment of the present invention is carried out when TIG arc is used as high-density heating energy.

FIG. 1 shows the situation before the start of treatment, and shows the area on the surface of the metal base material 1 where an alloyed layer is to be formed.
The alloying material 2 is placed in the area ). and the second
As shown in the figure, by reciprocating the TIG arc torch 3 in the length direction of the area to be treated over almost its entire length, the position of the arc 4 generated between the torch 3 and the metal base material 1 can be adjusted. In other words, the application position of high-density heating energy moves back and forth in the length direction of the area to be treated, thereby uniformly melting the alloying material and the surface layer of the metal base material in the area to be treated, and thereby melting the entire length of length 2. A uniform molten pool 4 is formed throughout.

What if we then cut off the current in torch 3 and extinguish arc 4? Solidification proceeds substantially simultaneously throughout the 'fl FA' A pool 5, forming an alloyed layer 6 shown in FIG.

Here, the length of the area to be simultaneously alloyed by reciprocating the application position of high-density heating energy such as TIG arc! ,
In other words, the reciprocating distance of the high-density heating energy application position 2
If it is less than 10Irvr1, there is no particular advantage to moving it back and forth, so the distance of the round trip! was set to be 10 an or more. In other words, in a short region of less than 10 m in length, even if the application position of high-density heating energy is fixed without moving, the entire region is simultaneously alloyed to form an alloyed layer with a relatively uniform alloy composition. I'm happy because I can do what I can.

Moreover, especially when using TIG arc as high-density heating energy, the above-mentioned reciprocating distance! The upper limit of 30 mm, and the reciprocating frequency (Hz) of high-density heating energy (TIG arc)
It is preferable that the reciprocating distance (approximately equal to the length of the part to be treated!) is within the range shown in FIGS. 4 and 5 depending on the arc current. Further, it is preferable that the arc current of the TIG arc is within the range of 150 to 400A.

Their output is as follows.

That is, in the case of the alloying treatment method of this invention, the high density force u
The reciprocating movement of the application position of thermal energy must result in a uniform molten state over the entire length of the processing area, or the factor for achieving a uniform molten state is the reciprocating distance of high-density heating energy! There are also conditions for reciprocating speed (reciprocating frequency) and arc current value. And first, the round trip distance! When the TIG arc exceeds 30M, it is not possible to maintain a uniform molten pool unless the reciprocating speed of the TIG arc is extremely fast; however, if the reciprocating speed is made extremely fast, the arc It is not stable and the melting becomes non-uniform. Therefore, the round trip distance of the TIG arc! is preferably 30 rrvn or less (within the range of 10 to 30 m, including the above-mentioned condition of 10 M or more).

Also, even if the reciprocating distance 2 of the TIG arc is within the range of 10 to 30M, that distance! However, if the reciprocating speed (reciprocating frequency) is too low, holding the molten pool uniformly becomes rotation, and this relationship also changes depending on the arc current value; the lower the arc current value, the faster the reciprocating Movement speed must be increased. Specifically, when the arc current value is 300A, the round trip distance! is 10. Then, the reciprocating frequency is 1. If the value is less than H2, it will be difficult to maintain a uniform molten pool, and if the arc current value is 300A, the reciprocating distance! is 30 m, and if the reciprocating frequency is less than 38Z, it becomes difficult to maintain a uniform molten pool. And the arc current value is 30OA
The round trip distance! is 10~30rn! Round trip distance even between r &! The lower limit of the reciprocating frequency that can maintain the molten pool uniformly is determined by this, and it is preferable that the reciprocating frequency be within the shaded area in FIG. FIG. 5 shows such a relationship estimated on the safe side by dividing the arc current value within the range of 150 to 400 A into every 508.

In other words, in Fig. 5, if the arc current value is 150 A or more, 2
If it is less than 00A, it is the area above the curve P1, and if it is 200A or more and 250A, it is the area above the curve P2, 25O.
In the case of A or more and less than 30OA, the upper @ area of curve P3, 3
In the case of 00A or more and less than 350A, the region above the curve P4 is a preferable range, and in the case of 350A or more and less than 400A, the region above the curve P5 is a preferable reciprocating frequency range.

Furthermore, the arc current value itself is 150A.
If it is less than that, there is a risk that the surface layer of the metal base material will not be sufficiently melted. On the other hand, if it exceeds 400 A, it will be overheated too much, slowing down the solidification rate, and there is a possibility that it will not be possible to refine the structure of the alloyed layer by rapid solidification. Therefore, it is preferable that the arc current value is within the range of 150 to 400A.

Furthermore, even if the TIG arc treatment time exceeds 30 seconds, overheating may occur, resulting in a slow solidification rate, and there is a risk that the microstructure of the alloyed layer cannot be refined by rapid solidification. Therefore, it is preferable that the TIG arc treatment time be within 30 seconds.

In the above explanation, TIG is used as high-density heat energy.
Although the case where an arc is used is shown, it is of course possible to use not only the -IG arc but also a laser, an electron beam, a plasma arc, etc. as the high-density force u thermal energy.

Note that the metal base material to be stripped by the alloying treatment of the present invention is arbitrary, and can be applied to carbon steel, cast iron, forged steel, A2 alloy, etc., for example.

Further, the elements to be alloyed may be arbitrarily determined depending on the properties to be improved by alloying and the material of the metal base material. For example, when the metal base material is steel, cast iron, or forged steel, Cr, Co,
Mo, A! etc., and when the metal base material is A2 alloy, N1, Fe, etc. can be alloyed,
Of course, two or more elements may also be alloyed. Furthermore, the manner in which the alloying material containing these alloying elements is placed on the metal base material is optional, and the powder layer of the alloying material may be formed by coating using an arbitrary binder, or by thermal spraying or roughening. It can be placed in the form of a thin plate.

Examples [Example 11 JIS 5US410L low carbon stainless steel was used as a metal base material, and alloying treatment for alloying Cr on the surface layer was performed as follows.

That is, Cr powder is applied onto the metal base material using polyvinyl alcohol, and TIG is applied as high-density heating energy.
The alloyed layer was formed using an arc. In this case, T.I.G.
The torch was moved back and forth along the length of the treatment area. The alloying treatment conditions are as follows.

TIG output crab 250A TIG torch reciprocating frequency: 2Hz Processing length:
20m Processing time: EP regarding the composition of the alloyed layer created under conditions of 20 seconds or more
~As investigated by IA analysis, the average C of alloying, @
The r concentration is 25.1 wt%, and the Cr concentration in the alloyed layer
The concentration distribution was 24.4 to 25.8 wt%, and the variation in Cr concentration was less than ±3% of the average concentration.

[Example 2] The same metal base material used in Example 1 was subjected to a process of alloying Or18. The processing method and conditions are the same as in Example 1.

E PMA analysis of the composition of the obtained alloyed layer revealed that the average Cr concentration was 23.3 wt% and the average A! The concentration is 3.8 wt%, and the variation in concentration is Cr, A! In both cases, it was less than ±3% of the average 'a degree'.

[Comparative Example 11 In alloying Or on the same metal substrate used in Example 1, TIG arc was used as high-density heating energy, and the TIG torch was directed in one direction from one end of the processing area to the other. Alloying was performed by continuously moving the The processing conditions are as follows.

TIG out crab 250A TIG torch movement speed: 2m/'Sec processing length:
20# Number of processing times: 1 to 5 times Here, the number of processing times is defined as one continuous movement of the TIG arc in one direction from one end of the processing area to the other end. The number of times the process is performed twice or more means that the TIG arc is repeatedly applied to the same area twice or more.

For the alloyed layer treated with each number of treatments, EP to IA
The Cr concentration in the same alloyed layer was investigated by analysis.
'+RfX variations were investigated. The results are shown in FIG. 6 in correspondence to the number of times of processing. For reference, the Cr concentration variations due to the reciprocating process of Example 1 are also shown in FIG.

Further, the time required for processing is shown in FIG.

FIG. 7 also shows the processing time for the reciprocating process of the first embodiment.

As is clear from FIGS. 6 and 7, Embodiment 1 of the present invention
In the case of the reciprocating movement process of 20 seconds, the variation of the Cr concentration in the alloyed layer with respect to the average concentration could be achieved by ±3% or less, whereas in the case of the continuous movement process in only one direction of Comparative Example 1, When the number of treatments is only one, the variation in the average concentration of Crs degree is extremely large, exceeding 110%.
Although the variation decreases as the number of processing increases,
After 5 treatments, the variation in average concentration finally decreased to nearly ±3%, and the treatment time required up to that point was about 6 times that of Example 1.

From these results, it is clear that the method of the present invention can uniformize the composition of the alloyed layer more efficiently than the conventional method.

[Comparative Example 21 Alloying of Cr+Af was carried out in the same manner and under the same conditions as in Comparative Example 1. The results are shown in Comparative Example 1 shown in Figures 6 and 7.
The results were almost the same.

Effects of the Invention According to the alloying treatment method of the present invention, the i
When performing alloying treatment on a region with a length of 0 mm or more, the variation in the composition of the alloyed layer to be formed can be significantly reduced compared to conventional methods, and the composition can be made uniform.
Therefore, it is easy to form an alloyed layer with uniform properties, and the processing time required to form an alloyed layer with a uniform composition as described above is significantly shorter than conventional methods. Not only can efficiency be improved, but the energy cost required for processing can be significantly reduced.

[Brief explanation of the drawing]

Figures 1 to 3 are schematic cross-sectional views showing step-by-step the situation in which the method of this invention is implemented, and Figure 4 shows the arc current when using a TIG arc with high density and zero thermal energy. A diagram showing the appropriate range of the reciprocating distance of the arc and the reciprocating frequency at 30OA, and Figure 5 shows the reciprocating distance of the arc and the reciprocating frequency at each arc current value when TIG arc is used as high-density heating energy. Figure 6 is a graph showing the variation of the Cr concentration in the alloyed layer formed by the method of Comparative Example 1 with respect to the average concentration, corresponding to the number of treatments, and Figure 7 is a graph showing the same comparison. FIG. 8 is a graph showing the change in processing time for the method of Example 1, and is a schematic cross-sectional view showing a situation in which a conventional general alloying processing method is implemented. 1... Metal base material, 2... Alloying material, 3...
TIG torch, 4... TIG arc as high-density heating energy, 5... Molten pool, 6... Alloyed layer.

Claims (1)

[Claims] An alloying material containing an element to be alloyed is placed on the surface of a metal base material, and high-density heating energy is applied from above the alloying material to form the alloying material and the metal base below it. In the method of forming an alloyed layer on the surface of a metal base material by melting and integrating the surface layer and then rapidly solidifying the surface layer, when forming the alloyed layer on a region of 10 mm or more in length on the surface of the metal base material, The application position of high-density heating energy is reciprocated in the length direction of the region over almost the entire length thereof to uniformly melt the entire region, and then the application of high-density heating energy is stopped in that state. An alloying processing method using high-density energy characterized by cooling and solidifying the entire molten pool.