KR20240082028A - Manufacturing method of Co-Cr based welding rod - Google Patents

Abstract

The present specification includes the steps of preparing a metal raw material containing 25 to 35 Cr, 2 to 10 W, 0.5 to 2 C and the balance of Co and inevitable impurities in weight%, melting the metal raw material to produce a molten metal, the upper A method for manufacturing a Co-Cr based welding rod, comprising preparing a mold with a molten metal injection portion formed therein, heating the mold to 80 to 500° C., and injecting the molten metal into the molten metal injection portion to manufacture a welding rod. It's about.

Description

{Manufacturing method of Co-Cr based welding rod}

The present invention relates to a method of manufacturing a welding rod made of Co-Cr alloy.

When an appropriate amount of chromium (Cr), tungsten (W), nickel (Ni), molybdenum (Mo), etc. is included in a cobalt (Co) alloy, its strength increases significantly and its chemical and mechanical properties become excellent over a wide temperature range. Due to these advantages, despite the high price of cobalt (Co) and chromium (Cr), their use is increasing in internal combustion engines, heavy industry, and construction fields that require high-temperature corrosion resistance and wear resistance.

Meanwhile, research is also being conducted to develop welding methods and welding rods containing cobalt alloy for repair and repair of parts made of the cobalt alloy. For example, Japanese Patent Publication No. 2013-150992 introduces a hard spacing method using tig welding, and Korean Patent Registration No. 10-0914330 introduces a welding method for valves made of cobalt alloy. Japanese Patent No. 7108996 introduces welding powder.

However, cobalt alloys have different heat treatment conditions depending on each component within the alloy, making it difficult to mass-produce them through casting. Accordingly, optimal conditions for production through continuous casting are required.

Japanese Patent Publication No. 2013-150992 (2013.08.08.) Republic of Korea Patent No. 10-0914330 (2009.08.20) Japanese Patent No. 7108996 (2022.07.29.)

In order to solve the above problems, the present invention provides a method for manufacturing a welding rod containing a metal raw material containing 25 to 35 Cr, 2 to 10 W, 0.5 to 2 C in weight percent, and the balance of Co and inevitable impurities. The purpose.

The purpose of this process is to provide an optimized production method by comparing the temperature of the mold, the presence or absence of an exhaust port, and the injection speed.

One embodiment of the present invention for achieving the above object is to prepare a metal raw material containing 25 to 35% Cr, 2 to 10% W, 0.5 to 25% C and the balance Co and inevitable impurities in weight percent. A step of manufacturing molten metal by melting the metal raw material, preparing a mold with a molten metal injection part formed at the top, heating the mold to 80 to 500 ° C., and injecting the molten metal into the molten metal injection part to make a welding rod. It may include a manufacturing step.

In one embodiment, one or more exhaust ports may be formed at the bottom of the mold.

In one embodiment, the exhaust port may be formed to have a diameter of 0.3 to 12 mm.

In one embodiment, the metal raw material may be provided in powder or scrap form.

In one embodiment, the metal raw material may be provided by mixing the metal powder and the scrap at a weight ratio of 10:2 to 10:4.

In one embodiment, the metal raw material may be melted through a high-frequency melting process.

In one embodiment, the diameter of the welding rod may be 3 to 12 mm.

In one embodiment, the length of the welding rod may be 300 mm or more.

In one embodiment, the molten metal may be injected into the molten metal injection unit while being heated to 150°C or higher from the melting point of the metal raw material.

In one embodiment, the molten metal may be injected into the molten metal injection unit at an injection speed of 1.0 to 2.0 kg/s.

Through this, the present invention is a method of manufacturing a Co-Cr alloy welding rod, and it is possible to manufacture a Co alloy welding rod with a diameter of 3 to 12 mm and a length of 300 mm or more by optimizing the shape, temperature, injection speed, and injection temperature of the mold. By optimizing the process, the productivity of welding electrodes can be improved.

1 is a cross-sectional view of a mold for manufacturing a welding rod according to an embodiment of the present invention.
Figure 2 is a flowchart for explaining a method of manufacturing a welding rod according to an embodiment of the present invention.
Figure 3 is a diagram showing the shape of a mold according to an embodiment of the present invention.
Figure 4 shows the results of heat flow analysis to optimize injection speed.
Figure 5 is a photograph taken of a welding rod with an internal defect.
Figure 6 shows the results of heat flow analysis to compare the effects of the presence or absence of an exhaust port.

Hereinafter, the method for manufacturing a welding rod of Co-Cr alloy according to the present invention will be described in detail. The drawings introduced below are provided as examples so that the idea of the present invention can be sufficiently conveyed to those skilled in the art. Accordingly, the present invention is not limited to the drawings presented below and may be embodied in other forms, and the drawings presented below may be exaggerated to clarify the spirit of the present invention. At this time, if there is no other definition in the technical and scientific terms used, they have meanings commonly understood by those skilled in the art in the technical field to which this invention pertains, and the gist of the present invention is summarized in the following description and attached drawings. Descriptions of known functions and configurations that may unnecessarily obscure are omitted.

The present invention relates to a method of manufacturing a welding rod whose base material is made of a Co-based alloy, and more preferably, to a method of manufacturing a welding rod made of a metal raw material of a Co alloy containing Cr, W, and C based on Co.

According to an embodiment, the metal raw material may be metal powder or scrap containing 25 to 35% Cr, 2 to 10% W, 0.5 to 2% C by weight and the balance of Co and inevitable impurities.

According to an embodiment, the metal raw material may further include 3% or less of Ni, 3% or less of Fe, 2% or less of Si, 0.5% or less of Mn, and 1.5% or less of Mo in weight percent.

According to an embodiment, the metal raw material may be a Stellite alloy, more preferably a Stellite-6 alloy, but is not limited thereto.

According to an embodiment, the present invention can melt the metal raw material through a high-frequency melting process. Specifically, the metal raw material can be charged into a high-frequency induction melting chamber using a predetermined crucible. Afterwards, the chamber is formed in a predetermined vacuum atmosphere, and an eddy current can be induced on the surface of the subject by flowing alternating current through a high-frequency induction coil surrounding the crucible. As the temperature rises due to this eddy current, the metal raw material can be melted.

According to an embodiment, during the high-frequency melting process, the dissolution chamber may form a vacuum atmosphere with a vacuum degree of 1 x 10 ^-2 to 1 x 10 ^-3 torr. If ^the vacuum degree exceeds ¹ However ^, even if ^the vacuum exceeds ¹ do.

According to an embodiment, the present invention can manufacture a welding rod by injecting molten metal melted through a high-frequency melting process into a predetermined mold. At this time, the mold may have a molten metal injection portion formed at the top and one or more exhaust ports at the bottom.

1 is a cross-sectional view of a mold for manufacturing a welding rod according to an embodiment of the present invention.

Referring to FIG. 1, the mold 100 according to an embodiment of the present invention may include a molten metal injection part 110, one or more molding grooves 130, and an exhaust port 150 communicating with the molding grooves.

Specifically, a molten metal injection part 110 is formed at the top of the mold 100 to receive molten metal, and a molding groove 130 extending from the top to the bottom is formed, so that the molten metal flows into the molding groove 130. It solidifies along the line and can be cast into a welding rod. In this process, the mold 100 may include one or more exhaust ports 150 at the lower end of the molding groove 130. Through the exhaust port 150, the present invention can discharge air remaining in the molding groove 130 out of the mold 100 during the molten metal injection process.

According to an embodiment, the diameter of the exhaust port may be manufactured to be 0.5 to 2 mm. If the diameter of the exhaust hole is less than 0.5 mm, it is difficult to completely discharge the air layer remaining inside the molding groove 130 out of the mold 100. In this case, the molten metal may not be completely injected to the bottom of the forming groove 130, and the welding rod may be separated when solidified.

Conversely, if the diameter of the exhaust port exceeds 2 mm, the injection speed of the molten metal increases excessively, and some of the molten metal is lost due to the exhaust port, so the density of the welding electrode may not be uniform. In this case, stress concentration occurs at a point where the density of the welding electrode is low, which may cause a sharp decrease in the strength of the welding electrode.

In Figure 1, the exhaust port 150 is described as extending in the vertical direction from the bottom surface of the molding groove 130, but it is not limited to this and may be formed on the side of the molding groove 130.

According to an embodiment, the mold 100 may be formed with two or more molding grooves 130 that communicate with one molten metal injection part 110. Hereinafter, two or more molding grooves 130 in communication with one molten metal injection part 110 are divided into a first molding groove (130a), a second molding groove (130b), a third molding groove (130c), and a fourth molding groove ( 130d), a first exhaust port (150a), a second exhaust port (150a), a third exhaust port (150a), and a fourth exhaust port (150a) communicating with each molding groove may be formed, but is not limited thereto, and more or It is obvious that it can be formed as follows.

According to an embodiment, the mold 100 may be manufactured from a graphite material, and more preferably, may be provided as a graphite mold coated with zirconia (ZrO ₂ ) on the inside.

According to an embodiment, a coupling hole (P) capable of combining the left and right molds may be formed on one cross section of the mold 100.

The configuration of the present invention has been described above. Hereinafter, a method for manufacturing a welding rod of Co-Cr alloy according to an embodiment of the present invention will be described.

Figure 2 is a flowchart for explaining a method of manufacturing a welding rod according to an embodiment of the present invention.

According to an embodiment, the Co-Cr based welding rod manufacturing method (S100) includes 25 to 35% Cr by weight, 2 to 10 $ W, 0.5 to 2% C, and the balance of Co and inevitable impurities. Preparing a metal raw material including (S110), melting the metal raw material to produce molten metal (S130), preparing a mold including a molten metal injection part at the top and one or more exhaust ports at the bottom ( S150), heating the mold to 80 to 500° C. (S170), and injecting the molten metal into the molten metal injection part to manufacture a welding rod (S190).

S110

In step S110, metal raw materials can be prepared. The composition of the metal raw material has been described previously and is therefore omitted.

According to an embodiment, the metal raw material may include scrap of Co-Cr based alloy. However, when all of the metal raw materials are used as scrap of Co-Cr alloy, the density of the metal raw materials is low, so a considerable amount of time is required to melt the metal raw materials, and in some cases, melting may not be possible. For this reason, the present invention can be used by processing scrap into chip form to form metal chips, and by mixing scrap and metal chips. At this time, the processing method may use pressurization or plasma melting, but is not limited thereto.

According to an embodiment, the metal raw material may be a mixture of the metal chips and the scrap in a ratio of 10:2 to 10:4 by weight. If the weight ratio of the metal chips to the scrap is less than 10:2, there is an advantage that the metal chips are relatively large and melt quickly, but there is a disadvantage that temperature control is difficult and the recyclability of the metal scrap is reduced. Conversely, if the weight ratio of the metal chip to the scrap exceeds 10:4, there is a disadvantage in that some of the scrap is not melted and it is difficult to melt.

S130

In step S130, the metal raw material may be melted through a high-frequency melting process, and more preferably, the metal raw material is charged into a high-frequency induction melting chamber using a predetermined crucible and then melted at 1 x 10 ^-2 to 1 x 10 ^-3 torr. It can be melted at a vacuum level of . The specific process of the high-frequency melting process has been described previously and is therefore omitted.

According to an embodiment, during the high-frequency melting process in step S130, the melting temperature may rise to about 2,000°C. For this reason, it is desirable to use a crucible made of W, Zr or a material coated with W and Zr during the high-frequency melting process. If the crucible uses Mo used in a typical high-frequency melting process, if the melting temperature exceeds about 1,000°C, Mo ₂ may be formed during the melting process. Alternatively, when Ti and Ta materials are used in the crucible, intermetallic compounds such as TiCr ₂ and TaCr ₂ may be formed by reacting with Cr in the metal raw material during the melting process, thereby contaminating the crucible and the molten metal. For this reason, it is preferable to use W and Zr, which do not react with Cr and have excellent thermal stability even at temperatures below 2,000°C, so no reaction occurs, and even more preferably zirconia (ZrO ₂ ) material or zirconia inside. A crucible made of a material coated with (ZrO ₂ ) can be used.

S150, S170

In step S150, a mold can be prepared, and in step S170, the prepared mold can be heated to 80 to 500°C. The shape and characteristics of the mold have been described previously, so they will be omitted.

If the temperature of the mold is less than 80°C, the molten metal may not be uniformly injected along the molding groove of the mold and a cold shut may occur. Due to the above-described decoction, the welding rod is cut and cannot be formed in a complete form.

Conversely, if the temperature of the mold exceeds 500°C, the temperature of the mold is too high and the solidification rate is excessively reduced, which may lead to the formation of pores inside the welding electrode. As a result, the welding electrode can easily break during or after solidification. Additionally, if an exhaust port is formed in the mold, the fluidity of the molten metal may increase excessively and some of the molten metal may be lost through the exhaust port.

For this reason, the temperature of the mold is preferably 80 to 500°C, and more preferably 90 to 400°C.

S190

In step S190, a welding rod can be manufactured by injecting molten metal into the molten metal injection part. According to an embodiment, step S190 may be performed through a rotation motor formed in the crucible, and more preferably, the molten metal may be injected into the molten metal injection unit at an injection speed of 1.0 to 2.0 kg/s through the rotation motor. there is.

If the molten metal injection speed is less than 1.0 kg/s, the molten metal injection amount is insufficient to completely push out the air layer inside the mold, and the molten metal may be mixed with air. As a result, casting defects such as pore formation may occur and the welding electrode may separate. Conversely, if the injection speed of the molten metal exceeds 2.0 kg/s, some of the molten metal may be discharged and lost through one or more exhaust holes formed at the bottom of the mold, and the possibility of defects due to eddy currents increases. For this reason, the molten metal is preferably injected into the molten metal injection unit at an injection speed of 1.0 to 2.0 kg/s, and more preferably at 1.5 to 1.8 kg/s.

Hereinafter, the present invention will be described in more detail through examples. However, it should be noted that the following examples are only for illustrating and explaining the present invention in more detail, and are not intended to limit the scope of the present invention. This is because the scope of rights of the present invention is determined by matters stated in the patent claims and matters reasonably inferred therefrom.

Metal chips made of Co-Cr-based alloy and welding rod scrap made of Co-Cr-based alloy were mixed in a ratio of 7:3 to prepare metal raw materials, and then melted through a high-frequency melting process. Specifically, metal raw materials were charged into an alumina crucible coated with zirconia (ZrO ₂ ), and then a current of 600 A at 8x10 ^-5 torr was injected into a high-frequency induction coil to melt the metal raw materials. At this time, the specific composition of the metal chip and welding rod is Cr: 32%, W 4.5%, C: 1.2%, Ni 3.0%, Mo 1.0% or less (excluding O), Fe 3.0%, Si 2.0%, and the remainder Co. and contains inevitable impurities.

Afterwards, a mold with an exhaust port at the bottom of the molding groove and a mold without an exhaust port were prepared in an Ar atmosphere, and molten metal was injected. At this time, the shape of the mold is as shown in Figure 3, the diameter of the molding groove is 5 mm, 8 mm, and 10 mm, and the length is 300 mm, and the diameter of the exhaust port is changed from 0.5 mm to 2 mm and repeated experiments are performed. did. The temperature and injection speed of the mold when injecting molten metal are shown in Table 1 below.

presence or absence of exhaust port Mold temperature (℃) Injection rate (kg/s) Example 1 O 400 1.6 Example 2 O 100 1.6 Comparative Example 1 O 400 0.54 Comparative Example 2 O 400 0.7 Comparative Example 3 O 400 2.4 Comparative Example 4 O 400 2.8 Comparative Example 5 X 400 1.6 Comparative Example 6 X 400 2.4 Comparative Example 7 X 400 2.8 Comparative Example 8 X 100 1.6

Figure 4 is the result of heat flow analysis to optimize the injection speed, Figure 5 is a photograph of a welding rod with an internal defect, and Figure 6 is the result of heat flow analysis to compare the effect of the presence or absence of an exhaust port.

Referring to FIG. 4, as a result of performing a heat flow analysis under the conditions in Table 1, when molten metal is injected into the mold under the conditions of Example 1 ((a) of FIG. 4), the molten metal is injected at the same temperature throughout the molding groove. You can see that it is injected evenly. On the contrary, it was confirmed that in Comparative Example 1 (FIG. 4(b)) and Comparative Example 2 (FIG. 4(c)), the tip was separated due to the air layer in the molding groove, and the molten metal and the air layer were mixed. As a result, it was confirmed that defects occurred in the welding electrode due to insufficient filling of the molten metal and internal pores, as shown in Figure 5.

In the case of Comparative Examples 3 and 4, the injection state of the molten metal was similar to Example 1, but the molten metal was lost through the exhaust port, and forming a welding rod of the desired size failed.

If the exhaust port was removed at the same injection speed as in Comparative Examples 5 to 7, the air layer in the molding groove was not discharged, and pores and defects were formed similar to Comparative Examples 1 and 2.

Through this, in order to manufacture a Co-Cr welding rod with a diameter of 3 to 12 mm and a length of 300 mm or more, the present invention heats the mold to 80 to 500 ° C and injects molten metal into the mold at an injection speed of 1.0 to 2.0 kg / s. It can be confirmed that it is desirable to do so.

Meanwhile, referring to Example 2 and Comparative Example 8, in Comparative Example 8 (FIG. 6 (a, c)) in which no exhaust hole was formed, the air layer in the molding groove was not released and a predetermined pressure was formed at the bottom of the molding groove. On the other hand, it can be seen that Example 2 (Figure 6(b, d)) in which the exhaust port was formed had an even pressure in the molding groove direction without pressure being formed. Afterwards, a comparison in which the exhaust port was not formed when the molten metal was injected In Example 8 (FIG. 6(a, c)), stagnation occurred when molten metal was injected due to air remaining in the molding groove, and in the actually manufactured welding rod, the tip of the welding rod solidified due to the stagnation, shortening the length of the welding rod, On the contrary, it was confirmed that some of the welding rods were separated. In Example 2 (Figure 6 (b, d)), where the exhaust port was formed, the electrode was filled evenly without solidification and no defects occurred after casting.

Through this, it can be confirmed that in order to manufacture a Co-Cr welding rod with a diameter of 3 to 12 mm and a length of 300 mm or more in the present invention, it is desirable to form an exhaust port with a diameter of 0.5 to 2 mm at the bottom of the mold.

Lastly, in order to optimize the injection temperature of the molten metal when the mold temperature was maintained at a low temperature of 200°C or lower, the injection flow rate was set to 1.6 kg/s, the mold temperature was 100°C, and the diameter of the mold was 5 mm in the previous example. , the height was fixed at 300 mm, and the molten metal was injected into the injection section while the molten metal was heated to 100°C or higher from the melting point (1,330°C) of the metal raw material. The injection temperature at this time and the presence or absence of casting defects are shown in Table 2 below.

Melting point (℃) Additional heating temperature (℃) Injection temperature (℃) presence or absence of exhaust port casting defects Example 11 1,330 170 1,500 O X Comparative Example 12 1,330 130 1,460 X Tip separation occurs Comparative Example 13 1,330 170 1,500 X Tip separation occurs

Referring to Table 2 above, when the injection flow rate was 1.6 kg/s and the mold temperature was 100°C, Comparative Example 12 was additionally heated to 130°C based on the melting point of the metal raw material, and Comparative Example 13 was additionally heated to 170°C. Tip separation occurred due to excessively low mold temperature.

However, Example 11, in which the exhaust port was formed, produced an intact welding rod without any casting defects. This means that when the mold temperature is 200°C or lower, more preferably 400°C or lower, and more preferably 80 to 200°C, casting defects occur due to excessively low mold temperature, but an exhaust port of 0.5 to 2 mm is provided. This is evidence that proves that if the formation is abnormal, the air inside the mold is naturally released and mixing of air and molten metal is prevented, thereby preventing casting defects. In addition, it is expected to be applicable to continuous casting processes in the future as the air layer within the mold is naturally released without a separate exhaust process and the molten metal is smoothly injected into the mold.

In other words, if the molten metal injection speed is 1.0 to 2.0 kg/s and the mold temperature is 80 to 200 ℃, the metal raw material is heated to 150 ℃ or more at the melting point, and if one or more exhaust holes are formed, the diameter is 0.5 to 2 mm long. Welding rods over 300 mm can be manufactured.

From another perspective, if the injection speed of molten metal is 1.0 to 2.0 kg/s and the temperature of the mold is 80 to 200°C, the injection temperature is 1,480 to 1,600°C, and if one or more exhaust ports are formed, the diameter is 0.5 to 2 mm in length. Welding rods over 300 mm can be manufactured.

Above, the present invention has been described in detail using preferred embodiments, but the scope of the present invention is not limited to the specific embodiments and should be interpreted in accordance with the appended claims. Additionally, those skilled in the art should understand that many modifications and variations are possible without departing from the scope of the present invention.

100: Mold for manufacturing welding rods
110: Molten metal injection part
130: Molding groove
150: exhaust port

Claims (11)

Preparing a metal raw material containing 25 to 35% by weight of Cr, 2 to 10% of W, 0.5 to 2% of C and the balance of Co and inevitable impurities;
manufacturing molten metal by melting the metal raw material;
Preparing a mold with a molten metal injection portion formed at the top;
Heating the mold to 80 to 500°C; and
Manufacturing a welding rod by injecting the molten metal into the molten metal injection part. According to paragraph 1,
A method of manufacturing a Co-Cr based welding rod, wherein one or more exhaust ports are formed at the bottom of the mold. According to paragraph 2,
A method of manufacturing a Co-Cr based welding rod, wherein the exhaust port is formed with a diameter of 0.5 to 2 mm. According to paragraph 1,
The metal raw material is a Co-Cr-based welding rod manufacturing method including a metal chip processed from a Co-Cr-based alloy scrap into a chip shape and a Co-Cr-based alloy scrap. According to paragraph 4,
The metal raw material is provided by mixing the metal chips and the scrap at a weight ratio of 10:2 to 10:4. According to paragraph 4,
A method of manufacturing a Co-Cr based welding rod, wherein the metal raw material is melted by a high-frequency melting process. According to clause 6,
The metal raw material is charged into a high-frequency induction melting chamber and then melted at a vacuum degree of 1 x 10 ^-2 to 1 x 10 ^-3 torr. According to paragraph 1,
A method of manufacturing a Co-Cr based welding rod, wherein the diameter of the welding rod is 3 to 12 mm. According to paragraph 1,
A method of manufacturing a Co-Cr based welding rod, wherein the length of the welding rod is 300 mm or more. According to paragraph 1,
A method of manufacturing a Co-Cr based welding rod in which the molten metal is injected into the molten metal injection part while being heated to 150° C. or higher from the melting point of the metal raw material. According to paragraph 1,
A method of manufacturing a Co-Cr based welding rod, wherein the molten metal is injected into the molten metal injection unit at an injection rate of 1.0 to 2.0 kg/s.