JP2015224385A - NbC DISPERSION STRENGTHENED HASTELLOY BASE ALLOY, METHOD FOR PRODUCING THE SAME, STEEL HAVING CORROSION RESISTANT-WEAR RESISTANT SURFACE BUILD-UP WELD LAYER, METHOD FOR PRODUCING THE SAME, AND COLD TOOL - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alloy and a steel combining cold wear resistance and corrosion resistance and not conventionally present, methods for producing them, and a relatively inexpensive cold tool produced from the alloy and steel.SOLUTION: As a steel 1 in which a build-up weld layer 3 is formed on the surface of a metallic material to be formed into a base material 2 by a plasma powder build-up welding technique such as build-up welding, a mixture obtained by dispersing a small amount of the fine particles of niobium carbide with the average particle diameter below 45 μm into a Hastelloy is applied upon the welding, thus the wear resistance provided in the niobium carbide is imparted without damaging the wear resistance characteristically provided in the Hastelloy. Further, as the alloy in which the fine particles of the niobium carbide below 45 μm are dispersed into the Hastelloy, it is a new NbC dispersion strengthened Hastelloy combining corrosion resistance and wear resistance.

Description

  From a new alloy with high corrosion resistance and wear resistance, a steel material with a build-up weld layer made of this alloy on the surface of the base metal and having high corrosion resistance and wear resistance, and from these alloys and steel materials The present invention relates to a manufactured cold tool.

  Currently, it is said that, as an alloy material used in a strong corrosive environment, only Hastelloy, which is a high nickel (Ni) -based alloy, exists at present. However, there is a problem that Hastelloy has poor wear resistance and cannot be used as a sliding member that comes into contact with a contact object with a strong frictional force. On the other hand, cobalt (Co) based alloys such as stellite are known as alloys having excellent wear resistance. However, stellite has poor corrosion resistance and cannot be used in a corrosive environment.

  As a tool and apparatus used in a strong corrosive environment, a rotor for a synthetic rubber kneader can be exemplified. In the field of a rotor for a synthetic rubber kneader, a carbon steel base material is known in which a Ni-based or Co-based self-fluxing alloy is spray-coated (see Patent Document 1). However, the thermal spraying technique can only form a relatively thin thermal spray coating on the surface of the base material, and has a great problem that it is poor in metallurgical bonding with the base material and easily causes peeling.

  Under such circumstances, hastelloy is often used for rotors for synthetic rubber kneaders, giving priority to corrosion resistance and presuming replacement in a short period of time. In other words, it has hitherto been considered that there is no alloy having wear resistance, particularly a weld metal, which can be suitably used in a strong corrosive environment. For this reason, there are currently no weld metal equipment materials and tool materials that have both high corrosion resistance and high wear resistance properties. There are no countermeasures, and equipment costs and tool costs are extremely high. However, the equipment operating environment in the material processing industry is becoming harsher, and the demand for wear resistance in a highly corrosive environment of equipment and tools is becoming higher. Therefore, an alloy material that has both high corrosion resistance and high wear resistance, which has never existed before, has been demanded.

  As one of the techniques for improving the hardness of the base material surface of an alloy, a technique for forming a metal-carbide composite film containing niobium carbide (NbC), which is a hard substance, on a metal surface by welding has been proposed (for example, patents). Reference 2 and Patent Reference 3). The technique disclosed in Patent Document 2 is made of NbC powder and stainless steel powder on the surface of a base material such as carbon steel, alloy steel, stainless steel, or Ni-based alloy as a plug used in seamless pipe mill rolling. A metal-carbide composite film is formed from a mixed powder of matrix metal by a plasma powder overlaying method. On the other hand, the technique disclosed in Patent Document 3 is a tool for hot working and a plug of seamless pipe steel, on the surface of a base material such as carbon steel, alloy steel, stainless steel, nickel base alloy, NbC powder and Co base. A metal-carbide composite coating is formed from a mixed powder of a matrix metal made of an alloy or a Ni-based alloy by a plasma powder cladding method or the like.

Japanese Patent Laid-Open No. 2003-277861 JP-A-9-52105 JP 2007-160338 A

  However, the techniques disclosed in Patent Documents 2 and 3 are applied to hot tools, and the wear resistance evaluation in the hot and the wear resistance evaluation in the cold are performed in the use environment, particularly in the temperature environment. Since the appearance and form of the worn part are completely different from each other, the condition applied to the hot tool cannot be diverted to the condition applied to the cold tool. One of the reasons is that in the techniques described in Patent Documents 2 and 3, huge NbC grains of about 100 μm are used, but the hardness of NbC is extremely high, and such a huge hard substance is on the surface. If the tool that is present in the cold is used, the surface of the workpiece that comes into contact with the tool will be scratched, whereas the workpiece will be hot during the hot process, and the surface layer will be oxide after processing. It is said that there will be no real harm even if a flaw is attached. That is, in the cold, the workpiece is shipped as a product as it is, so there is a significant difference from the hot that the scratch marks are not allowed to remain. In addition, as a material for a cold tool, there has been no reported example of an alloy in which NbC is dispersed in Hastelloy or a steel material in which such an alloy is used as a surface overlay layer on the surface of a base material.

  Further, Patent Documents 2 and 3 disclose that the average particle diameter of NbC used is preferably about 65 to 135 μm. In the examples, the average particle diameter is 100 μm (Patent Documents 2 and 3) and 120 μm. Although the experimental example using NbC of (patent document 2) is disclosed, although this average particle diameter is relatively large, when NbC powder smaller than this range and not commercially available is used So far, the wear resistance has not been studied. For this reason, it has been said by those skilled in the art that NbC powder having a relatively small particle size cannot be welded, including plasma powder overlay welding, and this is believed to be a matter of course. This is probably due to the fact that

  In view of the above problems, the present invention is a novel alloy and steel material suitable for cold tools having both corrosion resistance and wear resistance properties, and relatively fine NbC powder is dispersed in Hastelloy. The main object of the present invention is to provide an alloy having such a structure and a method for producing the same, a steel material provided with such an alloy as a surface overlay layer, a method for producing the steel material, and a useful cold tool made of these alloys or steel materials.

  The novel alloy of the present invention is an NbC dispersion strengthened hastelloy alloy characterized in that niobium carbide powder having an average particle size of less than 45 μm is dispersed in hastelloy.

  In the present invention, NbC fine powder that is hard and wear-resistant is applied to Hastelloy that has been considered to be unable to weld NbC of fine particles, and that has heretofore been considered to be resistant to corrosion. It was the first successful dispersion and created a new alloy that combines both corrosion resistance and wear resistance. This NbC dispersion strengthened hastelloy alloy has extremely high corrosion resistance and wear resistance and can be used as a material for an unprecedented cold tool that can be used for a long time in a highly corrosive environment. It will be a thing.

  Here, Hastelloy is a general term for alloys whose corrosion resistance and heat resistance are improved by mixing a relatively large amount of molybdenum (Mo) and chromium (Cr) into a nickel (Ni) group, and the NbC dispersion strengthening of the present invention. As the type Hastelloy alloy, any Hastelloy alloy including the most common Hastelloy C276 and Hastelloy C22 can be appropriately selected and applied according to the required corrosive environment and cost.

  This NbC dispersion-strengthened hastelloy alloy can be manufactured as an alloy by casting or plasma welding using a mixture of hastelloy powder and NbC powder having a particle size of less than 45 μm as a raw material. In the case of casting, it is possible to adopt a method in which NbC powder is poured into a melting furnace in which Hastelloy, which is a raw material of the alloy, is melted, and poured into a mold. In the case of plasma welding, a mixture of Hastelloy and NbC powder is overlay welded to an appropriate base material using a plasma powder welding (PTA welding) method that can supply a high temperature. A method of extracting only the overlay welding layer can be employed.

  In producing the NbC dispersion strengthened hastelloy alloy of the present invention, it is desirable that the weight ratio of niobium carbide powder in the powder mixture of hastelloy and niobium carbide is more than 0% and 50% or less. Niobium carbide powder is premised on a weight ratio exceeding 0% (necessary to mix niobium carbide powder with Hastelloy powder), but if the weight ratio exceeds 50%, it will be obtained. In the present invention, the niobium carbide powder is made of Hastelloy because it is considered that the obtained alloy cannot sufficiently exhibit the inherent corrosion resistance of Hastelloy and is not likely to be suitable for use in a strong corrosion environment. It can be said that it is appropriate to make it 0 to 50 weight% of a mixture with a powder. Within this range, the niobium carbide powder may be appropriately mixed in accordance with the required wear resistance and corrosion resistance, but the weight ratio of the niobium carbide powder in the mixture with Hastelloy is 5% to 30%. % Or less, an NbC dispersion strengthened hastelloy alloy having sufficient wear resistance and corrosion resistance can be obtained even with a relatively small amount of niobium carbide powder.

  When a relatively small amount of fine NbC powder of less than 45 μm is added and welded using Hastelloy powder as a matrix in this way, a part of the NbC powder in the obtained alloy is obtained during welding such as plasma welding. Although the surface layer of NbC is melted by heat (or in some cases up to the core), there is a possibility that some of the NbC may be bonded to adjacent NbC grains and become a lump of 45 μm or more. Is present as particles smaller than the size (45 μm) when charged, and niobium (Nb) and carbon (C) are not separated and remain as NbC. Since it is uniformly dispersed, wear resistance by NbC can be obtained without impairing the corrosion resistance of Hastelloy.

  The steel material according to the present invention is a steel material in which a build-up weld layer is formed on the surface of a metal material as a base material, and this build-up weld layer is the above-described NbC dispersion strengthened hastelloy alloy, that is, hastelloy. And an alloy in which niobium carbide powder having an average particle size of less than 45 μm is dispersed.

  The steel material according to the present invention is a steel material having, on the surface of the base material, a built-up weld layer that has a wear resistance not found in Hastelloy in combination with niobium carbide in addition to the corrosion resistance due to Hastelloy. In particular, as described above, an alloy in which very small niobium carbide powder having an average particle size of less than 45 μm is mixed in Hastelloy has not existed as described above, and it is completely new as a steel material having this alloy as a buildup weld layer As in the case of the NbC dispersion strengthened hastelloy-based alloy described above, it is extremely useful as a steel material used in a strong corrosive environment, particularly as a steel material requiring wear resistance in the cold.

  Unlike the thermal spray coating technology, the overlay weld layer can form a relatively thick layer, and the overlay weld layer and the base material are partially mixed, so that it is difficult to cause peeling problems. . Considering this and the durability of the build-up weld layer against wear under a general corrosive environment, it is sufficient that the average thickness of the build-up weld layer is 2 mm or more and 4 mm or less. In the case of forming a build-up weld layer of about 2 mm, the upper limit of the total thickness of the build-up weld layer is required when forming a build-up weld layer of two layers. Is 4 mm.

  On the other hand, the metal material applied to the base material in the steel material of the present invention is not particularly limited, but at the time of forming the build-up weld layer, the nickel in the hastelloy of the build-up weld layer is diluted and has corrosion resistance. Degradation should be avoided. Therefore, it can be said that a metal material made of an alloy containing nickel in a weight ratio of 8% or more and 57% or less is appropriate for the base material. Thus, as a metal material containing a relatively large amount of nickel (Ni), as an alloy containing a relatively large amount of nickel, austenitic stainless steel (SUS304 (Ni content 8 to 10.5%), SUS316L (Ni content) 10-14%), SUS309S (Ni content 12-15%)), Hastelloy (Ni content 57%), and the like. In other words, if the nickel content is low, the nickel in the Hastelloy is mixed with the base material at the time of build-up welding, and the corrosion resistance of the build-up weld layer may be reduced. Therefore, the lower limit of the nickel content is 8%, and as a material that does not cause a problem of dilution with the hastelloy of the build-up weld layer, the nickel content (57% when using hastelloy as a base material) ) Is the upper limit.

  Such a steel material of the present invention can be manufactured through a welding process in which a mixture of Hastelloy powder and niobium carbide powder is welded to the surface of a metal material as a base material by a plasma powder overlay welding method.

  In such a method for producing a steel material by PTA welding, it is desirable that the weight ratio of niobium carbide powder in the mixture with Hastelloy powder is more than 0% and 50% or less. The niobium carbide powder is premised to have a value exceeding 0% by weight in the powder mixture added at the time of welding (it is essential to mix the niobium carbide powder into the Hastelloy powder), but the weight ratio is 50 In the present invention, it is highly likely that the overlay weld layer cannot fully exhibit the inherent corrosion resistance of Hastelloy and is not suitable for use in a strong corrosion environment. It can be said that the niobium carbide powder is suitably 0 to 50% in the powder mixture. Within this range, the niobium carbide powder may be appropriately mixed in accordance with the required wear resistance and corrosion resistance, but the weight ratio of the niobium carbide powder in the mixture with the Hastelloy powder is 5%. If it is 30% or less, a build-up weld layer having sufficient wear resistance and corrosion resistance can be obtained even with a relatively small amount of niobium carbide powder.

  However, in addition to the above, in the above-described method for manufacturing a steel material according to the present invention, the type of Hastelloy, the mixing ratio of Hastelloy powder and Niobium carbide powder, the size of Niobium carbide powder, the type of base material, etc. Depending on the corrosive environment required, the degree of wear resistance, durability, cost, etc., various arrangements can be made as described above.

  Furthermore, the cold tool which concerns on this invention consists of the above-mentioned NbC dispersion strengthening type | mold hastelloy-type alloy, or is formed with the above-mentioned steel material, and set the build-up welding layer as a friction surface. Such a cold tool can be produced as follows, for example. First, a welding rod of NbC dispersion strengthened hastelloy alloy is manufactured in advance by a method such as casting. Thereafter, in order to maintain the tool strength, an inexpensive strength member such as carbon steel is used, and this is pre-formed or processed into a shape close to the tool shape. Then, build-up welding is performed at the required place on the surface using the welding rod. Of course, there is no problem even if this overlay welding is directly performed by PTA overlay welding. After the build-up welding is completed, the unevenness caused by welding on the welding surface is removed by machining such as cutting, and finished into a predetermined tool shape. It is also possible to produce a cold tool by the process as described above. In such a cold tool of the present invention, since the friction surface is in a state in which fine particles of niobium carbide are appropriately dispersed in Hastelloy, the tool is as in the case of using conventional niobium carbide particles. There is no risk of scratching the surface of the workpiece that comes into contact with the workpiece, and the quality and value of the workpiece as a product can be improved. In addition, since there has been no durable cold tool that has both corrosion resistance and wear resistance, the present invention can provide a completely new and useful cold tool particularly in the material processing industry. Is.

  The present invention is an alloy in which small particles of niobium carbide are dispersed in hastelloy, or a built-up weld layer composed of an alloy of hastelloy and niobium carbide is formed on the surface of the base metal. It is possible to provide a completely new alloy and steel material that have both the characteristics of both wear resistance and wear resistance of niobium carbide. In addition, this makes it possible for a useful cold tool manufactured from such an alloy or steel material to exhibit wear resistance in a highly corrosive environment, changing the situation that it had to be replaced frequently in the past. Thus, it is possible to newly supply a durable cold tool used in such a situation.

The general view which shows the steel materials which concern on one Embodiment of this invention, and its manufacturing process with a PTA welding apparatus. The optical microscope photograph which shows the state of the structure | tissue of the steel material which concerns on the same embodiment, and the overlay welding layer of a comparative example. The figure which shows the outline | summary of the cold wear test of the steel material which concerns on the same embodiment, and the test piece of a comparative example. The figure which shows the calculation outline | summary of the test piece which performed the same cold wear test, and wear depth. The graph which shows the result of the cold wear test. The graph which shows the result of the cold corrosion test of the steel material which concerns on the same embodiment, and the test piece of a comparative example.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, a steel material 1 according to an embodiment of the present invention includes a base material 2 and a build-up weld layer 3 formed on the surface of the base material 2. As described above, it is manufactured by a plasma powder overlay welding (Plasma Transferred Arc welding: hereinafter referred to as PTA welding) method.

  FIG. 1 is a schematic longitudinal cross-sectional view showing an overview of the main part of a PTA welding apparatus 4 applied to the present embodiment and the process of forming the build-up weld layer 3 on the base material 2. Since this welding apparatus 4 is a normal apparatus mainly including a PTA apparatus (only a torch is shown), it will be briefly described below. The torch 4 can be moved, for example, in the left-right direction in the figure by appropriate driving means (not shown). Specifically, the torch 4 includes a tungsten electrode 41, an inner wall 42, an intermediate wall 43, and an outer wall 44 in order from the inside. The inner wall 42 functions as a water-cooled nozzle. The tungsten electrode 41 and the inner wall 42 constitute a plasma gas supply nozzle, and the plasma gas PG supplied from above in the figure is sent out toward the tip of the torch 4. The inner wall 42 and the inner wall 43 constitute a plasma arc convergence and powder supply nozzle. The carrier gas CG supplied from above in the figure, Hastelloy powder serving as a matrix, and niobium carbide (NbC). The powder mixture 3 a is discharged from the tip of the torch 4. Further, the middle wall 43 and the outer wall 44 constitute a shield gas supply nozzle, and the shield gas SG supplied from above in the figure is injected from the tip of the torch 4. Reference numerals 45 and 46 denote a pilot arc power source and a plasma arc power source, respectively. The pilot arc power supply 45 is for generating a voltage between the tungsten electrode 41 and the base material 2, and the plasma arc power supply 46 is controlled to stabilize the generated voltage. For example, argon (Ar) gas is preferably used as the plasma gas PG, the carrier gas CG, and the shield gas SG.

  In the steel material 1 of the present embodiment, the base material 2 is made of stainless steel SUS316L (very low carbon steel, Ni content is 10 to 14% by weight) as a metal material containing a relatively large amount of nickel. In addition, an austenitic stainless steel such as SUS304 or SUS309L, or a metal material having a relatively high Ni content such as Hastelloy can be used as the base material 2.

  In this embodiment, Hastelloy C276 (Ni: 57%, Mo: 17%, Cr: 16%, Fe: 4-7%, W: 3-4.5) is used as the matrix of the overlay weld layer 3. %. Both are weight%). Others included in Hastelloy C22 (Ni: 52%, Mo: 13%, Cr: 22%, Fe: 3%, W: 3%, all weight percent) and other alloys collectively called Hastelloy Can be used. In the PTA welding method, Hastelloy is supplied as a powder.

  As the niobium carbide (NbC) mixed with the Hastelloy of the build-up weld layer 3, a powder having a particle size of less than 45 μm (hereinafter, this size of powder is referred to as “fine particles”) is applied. Since the commercially available NbC powder is a powder mainly composed of coarse particles having a particle size of 150 μm at the minimum, in this embodiment, the commercially available NbC powder up to 150 μm is passed through a sieve having a mesh size of 45 μm. To obtain fine granules. In the present embodiment, a plurality of test pieces are prepared by changing the weight ratio of the fine NbC particles to the mixture 3a with the Hastelloy powder. Specifically, a test piece of steel material 1 having five types of overlay weld layers 3 in which fine NbC particles were added in a range of 10 to 50% by weight in a mixture 3a with Hastelloy powder was prepared.

  In addition, for comparison with the overlay welding layer 3 in which NbC fine particles are mixed in Hastelloy, as a comparative example, instead of fine particles, a powder having a particle size of 45 μm or more and less than 75 μm (hereinafter referred to as “powder of this size” A test piece in which a build-up weld layer is formed on the surface of the base material by mixing Hastelloy) and a powder having a particle size of 75 μm or more and less than 150 μm (hereinafter, this size of powder is called “coarse”). A test piece in which the overlay weld layer was formed on the surface of the base material by mixing with Hastelloy was also formed. As in the case of fine particles, a commercially available NbC powder of about 150 μm was passed through a sieve having a mesh size of 75 μm to obtain medium particles, and the remaining particles were used as coarse particles. FIG. 2 shows a mixture 3a of powders added at the time of overlay welding, obtained by mixing NbC fine grains at 30% (a), medium grains at 30% (b), and coarse grains at 40% (c). The photograph of the build-up weld structure | tissue by the optical microscope photograph of the obtained build-up weld layer is shown. In each photograph, the gray part is Hastelloy, and the distorted grain-shaped lump dispersed in Hastelloy is NbC grains. The average particle size of the overlay weld layer 3 after PTA welding using NbC fine particles is 45 μm or less (the figure (a)) smaller than the particle size at the time of charging. The average particle size of the overlay welding layer 3 after PTA welding used is 45 μm or more and less than 75 μm (the same figure (b)) and 75 μm or more and less than 150 μm (the same figure (c)). It is. Some of the NbC particles in Hastelloy have agglomerated nearby NbC particles, but most exist as particles smaller than the particle size at the time of charging. As shown in FIG. 4C, when NbC coarse particles are used, welding is possible, but the welded NbC coarse particles have large pumice-like hole defects (black portions in the photograph). ) Was observed so much that the NbC coarse particles were judged to have a high welding failure rate, and the following wear test and corrosion test were not performed. Although black portions can be seen in the NbC fine and medium-sized photographs in FIGS. 4A and 4B, it is not at a level where the weld defect is high in the entire welded structure. In particular, in the build-up weld layer 3 of the present embodiment, it can be seen that the fine NbC particles are distributed almost uniformly throughout the entire welded structure.

  A steel piece A having a length of 30 mm, a width of 10 mm, and a height of 25 mm was prepared for the cold wear test and the cold corrosion test of the steel material 1 of the present embodiment (see FIG. 3). Among the height direction, the region of 22-24 mm (average thickness 23 mm) from the bottom is the base material Aa (2) made of stainless steel and SUS316L, and the region of 1-3 mm (average thickness 2 mm) from the surface is This is an overlay welding layer Ab (3) in which Hastelloy · C276 powder and NbC are formed on the surface of the base material Aa (2). Such steel materials 1 were prepared for five types of NbC fine particles of 10 to 50% by weight (10% increments) in the overlay welding layer Ab (3).

  As comparative examples, specimens A were prepared for 5 types of NbC medium grains of 10 to 50% by weight (in increments of 10%) in the overlay welding layer Ab, and only Hastelloy · C276 containing no NbC was used as a mother. A test piece A was welded on the surface of the material, and a test piece was also prepared in which the stellite, which is a cobalt-based alloy, was built-up on the surface of the base material Aa. The base material Aa of each test piece A is stainless steel SUS316L as in the steel material 1 of the present embodiment, and the above-described PTA method is also used as a method for forming the build-up weld layer.

  FIG. 3 is a schematic diagram of a cold wear test. The build-up weld layer Aa of the test piece A including the five types of steel materials 1 of the present embodiment was pressed against the disk 5 having a sliding surface of 125 mm in diameter made of stellite at room temperature of 25 ° C. (cold). A wear mark Ax as shown in FIG. 4 was formed on the test piece A with the rotational speed of the disk 5 being 30 revolutions per minute, the pressing load being 350 kPa, and the pressing time being 3 minutes. The measurement method of the wear mark Ax is that the specimen A after the wear test is observed from both sides, and the average value of the wear mark lengths L1 and L2 is the average wear length L (Equation (1) in the figure). The wear mark depth d was calculated using the value of L and the radius r of the disk 5.

  The measurement result of the wear scar depth about each test piece A is shown as a graph in FIG. The horizontal axis of the figure shows the NbC powder input rate (weight ratio,%) relative to the mixture 3a with Hastelloy · C276 powder when forming the build-up weld layer Ab (3), and the vertical axis is calculated. Shows the wear scar depth (μm) obtained. At the position of 0% on the horizontal axis, the wear scar depths of the overlay welding layer (▲ C276) made only of Hastelloy C276 and the overlay weld layer (● STL) made only of stellite are plotted for comparison. ing. The wear-resistant Hastelloy C276 overlay weld layer has a wear mark depth of 400 μm or more, while the Stellite overlay weld layer with excellent wear resistance shows almost no wear. I understand that there is no. On the other hand, in the built-up welded layer (■ NbC medium grain) in which NbC medium grains are added to Hastelloy C276, a disturbance was observed in the wear depth value in the low NbC medium grain injection rate region. Although it is inferior to stellite in the region of 20 to 50%, it has a wear depth of about 100 μm, and good wear resistance was recognized as compared with the overlay welding layer of Hastelloy · C276 alone. In the build-up welded layer (◆ NbC fine grain) in which the fine grain of NbC, which is the steel material 1 of this embodiment, is added to Hastelloy C276, the wear depth is stable at a low level regardless of the input rate, and 50% The wear depth was approximately 100 μm or less in all the following regions. That is, it can be said that when NbC fine grains are added to Hastelloy C276, cold wear resistance substantially equivalent to that of stellite can be obtained. In particular, the NbC fine particles have a good wear resistance in a small amount of 10%. Therefore, even if a very small amount of NbC fine particles is mixed with Hastelloy / C276 powder, It was demonstrated for the first time that high wear resistance was obtained.

Next, using each test piece A described above, a cold corrosion test was performed. The cold corrosion test was in accordance with JIS G0577 “Method for Measuring Pore Potential of Stainless Steel”. Investigate the time required for corrosion to proceed at a stroke as the test piece A is immersed in an 80 ° C (cold) corrosion solution (CaCl ₂ adjusted to pH with HCl) maintained at pH 3.0, increasing the potential difference. did. The result of the corrosion test about each test piece A is shown as a graph in FIG. The horizontal axis of the figure shows the NbC powder input rate (weight ratio,%) relative to the mixture 3a with Hastelloy · C276 powder when forming the build-up weld layer Ab (3), and the vertical axis shows the potential. (Poreelectric potential). As the value on the vertical axis is larger, corrosion is less likely to occur, so current is less likely to flow. The potentials of the overlay welded layer (▲ C276) consisting only of Hastelloy · C276 and the overlay welded layer consisting only of stellite (● STL) plotted at the position of the horizontal axis 0 are 0.8 and 0.6, respectively. there were. On the other hand, in the build-up weld layer (■ NbC medium grain) in which NbC medium grains are added to Hastelloy C276, disturbance in the potential (that is, the progress rate of corrosion) is observed due to the low NbC medium grain injection rate. It was shown that corrosion increases easily as the input rate is increased. In the built-up welded layer (◆ NbC fine particles) in which NbC fine particles, which are the steel material 1 of this embodiment, are added to Hastelloy · C276, Stellite and Hastelloy · C276 are used when the input rate is 10%, 30%, and 40%. Of 50%, the potential was slightly lower than Stellite, and 20% was higher than Hastelloy · C276. That is, in NbC fine grains, the corrosion progress rate is suppressed over the entire range of 10 to 50%, but the corrosion progress rate is strongly suppressed particularly when the input rate is 10 to 30%. It was close to the value of C276 alone, and it was demonstrated for the first time that it has a small decrease in the corrosion progress rate with an increase in the input rate in the low input rate region, in other words, it has high corrosion resistance.

  Considering the results of the above cold wear test and cold corrosion test comprehensively, when forming the build-up weld layer 3 on the surface of the base material 1, NbC fine grains or medium grains are added to Hastelloy C276 powder. With the added overlay weld layer 3, it is possible to obtain a steel material 1 having both cold wear resistance and corrosion resistance. In particular, NbC is preferably a fine particle having a particle size of less than 45 μm. In view of the results of the overlay welding layer of Hastelloy C276 alone, NbC fine particles having a weight ratio of 50% or less, particularly 5% or more and 30% or less of the powder mixture 3a during overlay welding were added. In some cases, it was found that cold wear resistance and cold corrosion resistance were obtained. That is, the build-up weld layer 3 in the steel material 1 of this embodiment is a completely new type of NbC dispersion strengthened hastelloy alloy having cold wear resistance and corrosion resistance, in other words, NbC dispersion strengthened hastelloy weld coating. You can say that.

  Therefore, if a cold tool is manufactured with the steel material 1 of this embodiment, it is only necessary to disperse a small amount of NbC fine particles in Hastelloy in the build-up weld layer serving as a friction surface. A novel and useful cold tool having both wear resistance and corrosion resistance can be provided to the market at a relatively low cost. When hard materials are dispersed in cold working tools, it has been thought up to now that the surface of the workpiece will be wrinkled, and there has been an industry situation that such tools have not been produced. The situation is the same also in the cold feeling tool used in a strong corrosive environment. Further, in the present invention, when NbC fine particles are introduced into Hastelloy and dispersed therein, it can be said that it is an epoch-making in the technical field that an effect more than originally expected is obtained. Examples of such a cold tool include a rotor for a kneader used in the synthetic rubber production field used in the above-mentioned strong corrosion environment, a screw or a cylinder of an extruder or a dryer, etc. In addition, the present invention can be applied to a tool used in a corrosive environment where hastelloy has been conventionally used, such as a carbon generation field and a ceramic generation field.

  The configuration of the present invention is not limited to the above-described embodiment. In the above embodiment, the steel material in which the build-up weld layer in which the fine particles of NbC are dispersed in the Hastelloy is formed on the surface of the base material has been described, but the NbC dispersion strengthened type having the same configuration as this build-up weld layer. A Hastelloy alloy can also be used. Furthermore, the base material in the steel material, the build-up weld layer, or the matrix material of the NbC dispersion strengthened hastelloy alloy can be changed without departing from the spirit of the present invention, or the NbC added to the alloy or the build-up weld layer can be changed. Changing the particle size and the charging rate can be changed as appropriate according to the environment used as a cold tool and the required specifications. In addition, the manufacturing method of the steel material or alloy including the overlay welding layer and the applied cold tool are not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  The present invention provides a new alloy and steel material having both corrosion resistance and wear resistance by an alloy in which niobium carbide is dispersed in hastelloy and a steel material formed on the surface of the base metal as a build-up weld layer. And a manufacturing method thereof, and a cold tool manufactured from such a steel material, and can be extremely useful in the field of metal materials and the material processing industry as its application.

DESCRIPTION OF SYMBOLS 1 ... Steel material 2 ... Base material 3 ... Overlay welding layer

Claims (12)

An NbC dispersion-strengthened hastelloy alloy obtained by dispersing niobium carbide powder having an average particle size of less than 45 μm in hastelloy. A method for producing the NbC dispersion-strengthened hastelloy alloy according to claim 1,
A method for producing an NbC dispersion strengthened hastelloy alloy, characterized in that an alloy is produced by casting or plasma welding using a mixture of the hastelloy powder and the niobium carbide powder having a particle size of less than 45 μm as a raw material. The method for producing an NbC dispersion-strengthened hastelloy alloy according to claim 2, wherein a weight ratio of the niobium carbide powder in the mixture is more than 0% and 50% or less. The method for producing an NbC dispersion strengthened hastelloy alloy according to claim 3, wherein a weight ratio of the niobium carbide powder in the mixture is 5% or more and 30% or less. A steel material in which a build-up weld layer is formed on the surface of a metal material as a base material,
A steel material, wherein the build-up weld layer is made of the NbC dispersion strengthened hastelloy alloy according to claim 1. The steel material according to claim 5, wherein an average thickness of the build-up weld layer is 2 mm or more and 4 mm or less. The steel material according to claim 5 or 6, wherein the base material is a metal material made of an alloy containing nickel in a weight ratio of 8% to 57%. A method for manufacturing a steel material according to any one of claims 5 to 7,
A method for producing a steel material, comprising: a welding step of welding a mixture of the Hastelloy powder and the niobium carbide powder to the surface of the metal material as the base material by a plasma powder overlay welding method. 9. The method for manufacturing a steel material according to claim 8, wherein in the welding step, a weight ratio of the niobium carbide powder in the mixture is set to more than 0% and 50% or less. The method for producing a steel material according to claim 9, wherein a weight ratio of the niobium carbide powder in the mixture is 5% or more and 30% or less. A cold tool formed of the NbC dispersion strengthened hastelloy alloy according to claim 1. A cold tool formed of the steel material according to any one of claims 5 to 7, wherein the build-up weld layer is set as a friction surface.

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