JP2017124414A - Fe-BASED ALLOY FOIL FOR BRAZING AND BRAZING FILLER METAL JOINING COMPONENT - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide Fe-based alloy foil for brazing and a brazing filler metal joining component therewith that is easy to manufacture by a conventional meltspining method and partial corrosion is not generated easily even if brazing filler metal joins metal containing Cr.SOLUTION: Fe-based alloy foil for brazing has an amorphous formation consisted of Fe, P of 8-15 mass% and inevitable impurities. Favorable P is 12-14 mass%. A brazing filler metal joining component has a brazing filler metal layer consisted of Fe, P of 8-15 mass% and inevitable impurities between a first metal and a second metal containing Cr because the Fe-based alloy foil for brazing is used. Favorable P is 12-14 mass%, and the brazing filler metal layer side of the first metal and the second metal can have diffusion areas of P.SELECTED DRAWING: None

Description

  The present invention relates to a brazing Fe-based alloy foil and a brazing joint member, and in particular, for example, a brazing Fe-based alloy foil suitable for brazing (brazing joining) between metal materials (base materials) such as stainless steel. The present invention relates to a brazing joint member in which it is used for melting brazing and metal materials are joined together.

  Conventionally, there is a brazing method as one of techniques for metallurgically joining various metal materials (base materials), for example, Fe-based alloy materials, Ni-based alloy materials, austenitic stainless steel materials, and ferritic stainless steels. It is applied to the joining of various metal materials (brazing joining). In the brazing method, metal materials (base materials) are joined to each other through a molten brazing material (melting brazing) obtained by heating a brazing material (brazing material) having a melting point lower than that of the metal material (base material). This is a method, and there are few restrictions on the shape and material of the metal material (base material), and a high-strength and sound joint structure (brazing joint member) can be easily produced.

  For example, Patent Document 1 discloses a sheet-like (foil-like), powder-like, or paste-like Fe-based brazing material containing powder, which is used for brazing stainless steel heat exchanger plates. On the other hand, Cr (9-30 wt%) and Ni (5-25 wt%), Si (0-25 wt%), B (0-6 wt%), P (0-15 wt%), Mn (0-8 wt%) %), C (0 to 2 wt%), and Hf (0 to 15 wt%), an Fe-based brazing material added with at least one element is described. And when brazing stainless steel using said Fe base brazing material, it describes that the stainless steel which is a to-be-joined material is heated for 15 to 45 minutes at the temperature of 1000-1150 degreeC.

  Further, for example, in Patent Document 2, Si (less than 6% by mass), B (0 to 2% by mass), and P (0 to 0% by mass) have the same composition as that of the plate-shaped heat exchanger that is the material to be joined. 15% by mass) of a powdery or foil-like Fe-based brazing material to which one or more elements are added, and it is essential to add Cr (0 to 40% by mass) to the base Fe In addition, Mn (0 to 16% by mass), Ni (0 to 25% by mass), N (0 to 1% by mass) and Mo (7% by mass or less) are added, and Si (less than 6% by mass) is added. ), B (0 to 2 mass%), and P (0 to 15 mass%), Fe-based brazing material to which one or more elements are added is described. The temperature at which the Fe-based brazing material is completely melted (liquidus temperature) is lowered by the action of individual or combination of Si, B, and P, and the liquidus temperature (complete melting temperature) is 1230 ° C. It should be stated that:

  Patent Documents 1 and 2 describe that the Fe-based brazing material can be provided in the form of powder, rod, or foil. In general, foil-type brazing materials are less pasteable than powder-type brazing materials that are applied as pastes, so they are easy to handle and contain less impurities and bubbles. Contamination in a heat treatment furnace that brazes, with high spreadability and high permeability, easy to form a preform by machining such as pressing, bending, cutting, etc. There are many advantages, such as being less scattered and not being easily scattered like powder brazing material. The foil-like Fe-based brazing material is, for example, an amorphous material obtained by a melt spinning method in which a molten metal material containing B rectified by a nozzle is rapidly solidified on the surface of a cooling roll in addition to a rolled foil. Is offered in quality alloy foil.

  In the melt spinning method described above, it is practically necessary to form a foil having an amorphous structure to suppress embrittlement and maintain the shape of the foil. Therefore, as described in Patent Documents 1 and 2, it is generally combined with B (boron) or P (phosphorus) having an amorphous forming ability and Si (silicon) for assisting the amorphous formation. Has been done. For example, in the example of Patent Document 1, 12% by mass of Si is added to B, and in the example of Patent Document 2, 1.0% by mass or more of Si is added to the total of B and P. .

Special table 2008-542030 JP-T-2004-529776

  It is considered that the Fe-based brazing materials described in Patent Documents 1 and 2 containing Fe as a base and a plurality of elements can be produced in the form of an Fe-based alloy foil by the melt spinning method. However, when a molten metal material containing a plurality of elements is used, the rectifying nozzle tends to be blocked or the foil becomes brittle.

  In addition, metal materials (base materials) that contain Cr and have improved mechanical strength, corrosion resistance, and hardenability are also in demand for brazing. On the other hand, when brazing is performed using an Fe-based alloy foil containing B, the metal contained in the molten brazing is along the crystal grain boundaries of the metal material (base material) or diffuses into the crystal grains. It combines with Cr contained in the material (base material) to produce a Cr boride, and a Cr-depleted layer is formed inside the metal material (base material). Therefore, corrosion tends to progress along the Cr-deficient layer, and the brazed joint member may be damaged due to a decrease in mechanical strength due to the local corrosion.

  An object of the present invention is an Fe-based alloy foil for brazing and a brazing joint using the same, which can be easily produced by a conventional melt spinning method, and local corrosion does not easily occur even when a metallic material containing Cr is brazed. It is to provide a member.

  In the course of studying a solution to the above-mentioned problem, the present inventor has come up with the idea of configuring a brazing foil by adding a single element to Fe as a base. Then, by selecting P having an amorphous forming ability, studying single addition, and defining the P content in an appropriate range, the inventors have found that the above-described problems can be solved, and have arrived at the present invention.

That is, the brazing Fe-based alloy foil of the present invention has an amorphous structure composed of Fe, 8 to 15% by mass of P, and inevitable impurities.
Moreover, it is preferable that said P is 12-14 mass%.

A brazing joint member can be obtained using the Fe-based alloy foil for brazing of the present invention.
That is, the brazing joint member of the present invention has a brazing material layer composed of Fe, 8 to 15% by mass of P, and unavoidable impurities between the first metal material and the second metal material containing Cr.
The P may be 12 to 14% by mass.
Further, a P diffusion region may be provided on the brazing material layer side of the first metal material and the second metal material.

  The brazing Fe-based alloy foil of the present invention is not easily clogged with the rectifying nozzle or embrittled in the foil when the foil is produced by the melt spinning method. Further, in the brazing joint member containing Cr using the Fe-based alloy foil for brazing of the present invention, local corrosion does not easily occur in practical use.

It is explanatory drawing for demonstrating the structure of the brazing joining member of this invention. It is explanatory drawing for demonstrating the example of the heat pattern used for the manufacturing method of the brazing joining member of this invention. It is explanatory drawing for demonstrating the structure of the cross-sectional structure | tissue of the brazing joining member which has the brazing filler metal layer containing B. FIG. 4 is an explanatory diagram for explaining a configuration of a partial region including a brazing filler metal layer and a metal material (base material) in the cross-sectional structure shown in FIG. 3.

  The brazing Fe-based alloy foil of the present invention has an amorphous structure composed of Fe, 8 to 15% by mass of P, and unavoidable impurities.

  That the brazing material is in the form of a foil as in the present invention, as described above, the mechanical strength of the brazed joint is difficult to decrease because there is less mixing of impurities and bubbles compared to the pasty brazing material, There are conveniences in producing a brazing joint member, such as easy formation of a preform by machining and simple continuous supply and automatic supply by winding in a coil shape. Moreover, when the foil-like brazing material is an Fe-based alloy foil as in the present invention, it can be provided at a lower cost than an alloy foil based on Ni or Co that is more expensive than Fe.

  The brazing Fe-based alloy foil of the present invention is an Fe-P alloy and contains P in the range of 8 to 15% by mass. P is different from B in which Cr boride is formed to form a Cr-deficient layer as described above, and a Cr-deficient layer is formed inside the metal material after brazing at the time of brazing a metal material (base material) containing Cr. Is difficult to form. Therefore, unlike the conventional brazing Fe-based alloy foil containing B, the Fe-based alloy foil for brazing of the present invention containing P in the above range and substantially free of B is caused by the Cr-deficient layer unlike the conventional brazing Fe-based alloy foil containing B. The risk of the occurrence of substantially harmful local corrosion can be avoided.

  Further, P is not as remarkable as B, but has an amorphous forming ability. Therefore, if the characteristics can be utilized well, an Fe-P alloy foil can be produced by applying the above-described melt spinning method. Therefore, in the present invention, the content of P with respect to the base Fe is specified in the range of 8 to 15% by mass, thereby making it easy to form an Fe-based alloy foil having suitable toughness and having an amorphous structure. To do.

  Further, among Fe-P based alloys, when P is in the range of 8 to 15% by mass, the melting point (liquidus temperature) is approximately 1200 ° C. or less, so a general metal material (base material) for brazing Brazing can be performed at a temperature of approximately 1250 ° C. or lower, which is lower than the melting point of). When P is in the range of 10 ± 0.3% by mass, the melting point can be approximately 1050 ° C., and when P is in the range of 9.5 to 11.5% by mass, the melting point can be approximately 1100 ° C. or less. . Thereby, preferable P amount can also be set with respect to preferable melting | fusing point. Also, by lowering the melting point, the required temperature for brazing can be reduced, which can contribute to energy saving. In addition, since the increase in the melting point with respect to the decrease in the P amount is more sensitive than the increase in the melting point with respect to the increase in the P amount, it is particularly important that P is 8% by mass or more.

Further, when the Fe-P alloy contains P exceeding about 16% by mass, Fe ₃ P and Fe ₂ P, which are hard and brittle intermetallic compounds, are generated. When an Fe-based alloy foil containing such an intermetallic compound is used for brazing, there is a risk that the mechanical properties (particularly elongation and squeezing) of the brazing joint will be reduced. Therefore, in the present invention, the upper limit of P is defined as 15% by mass, whereby the formation of the intermetallic compound is suppressed even when the amount of P varies within a common sense range, and the mechanical properties of the brazed joint are increased. The risk of characteristic degradation can be avoided.

  Moreover, since it is common that the supply source of P is iron phosphide whose amount of P is 15 mass% or less industrially, the versatile use of this iron phosphide is desired. Therefore, in the present invention, in addition to avoiding the risk of deterioration of the mechanical properties of the brazed joint described above, the upper limit of P is set to 15 mass% in consideration of the P content of the iron phosphide being 15 mass% or less. % Or less.

  The Fe-based alloy foil for brazing of the present invention is a foil-like brazing material having an amorphous structure that can be easily formed by machining. When importance is attached, it is preferable that P is 12 to 14% by mass.

  In the brazing Fe-based alloy foil of the present invention, since a single element P is selected and contained in the base Fe, when an element other than P is included, it is considered as an inevitable impurity mixed in unintentionally. It is done. For example, since iron phosphide (FeP) suitable as a general source of P has a purity of approximately 99.5% by mass, the Fe-based alloy foil using this as a raw material has approximately 0.5% by mass. There is a risk of containing impurities. Elements that are inevitable impurities such as Si (silicon), Mn (manganese), Mo (molybdenum), Ti (titanium), Nb (niobium), Cr (chromium), Ni (nickel), and B (boron) And the like are each preferably less than 0.01% by mass. Similarly, for example, C (carbon), S (sulfur), N (nitrogen), Al (aluminum), Cu (copper), and the like are each preferably less than 0.005% by mass.

  The brazing Fe-based alloy foil of the present invention can be produced by the melt spinning method (including a liquid quenching method such as a single roll method). For example, in an alloy melt mainly composed of iron phosphide (FeP), the components are adjusted so that P becomes a target value in the range of 8 to 15% by mass, maintained at a predetermined temperature, and rectified by a casting nozzle. It is ejected onto the surface of a copper alloy roll (cooling roll) that rotates at high speed. At this time, the slit-shaped opening provided at the tip of the casting nozzle is set to have an opening area corresponding to the thickness and width of the alloy foil to be cast. The molten alloy jetted onto the surface of the cooling roll from the opening of the casting nozzle in this manner is rapidly cooled and rapidly solidified as soon as it comes into contact with the surface of the cooling roll to form a foil-like solidified product having an amorphous cast structure. Form. And the Fe-based alloy foil of this invention (long exfoliation thing) can be produced by exfoliating the foil-like solidified substance from the surface of a cooling roll by air blow etc. continuously.

  The Fe-based alloy foil having the chemical components shown in Table 1 can be produced by changing the P amount relative to the base Fe by the manufacturing method described above. In addition, the comparative example 2 shown in Table 1 is Ni-based alloy foil which does not contain P substantially and utilizes the amorphous forming ability of B. In Table 1, the case of a long foil having an appearance in which no defects are recognized is indicated by “◯”, and Comparative Example 1 in which the production of the alloy foil is difficult is indicated by “x”.

  The structure of the alloy foils of Invention Examples 1 and 2 and Comparative Example 2 is, for example, an X-ray diffractometer equipped with a Cu target, and a test piece (alloy foil) at a diffraction angle in the range of 30 ° to 70 °. This can be confirmed by the presence or absence of diffraction peaks of diffracted X-rays from the surface. For example, a test piece (alloy foil) that cannot confirm any diffraction peak showing crystalline is determined to have an amorphous structure, and a test piece (alloy foil) that can check any diffraction peak showing crystalline is crystalline. It can be determined that some or all of the quality tissue is present.

  The toughness of the alloy foils of Invention Examples 1 and 2 and Comparative Examples 1 and 2 can be confirmed by performing a test in which a test piece (alloy foil) is bent, for example, at 180 °. For example, it is determined that a test piece (alloy foil) that bends with elasticity has toughness suitable for preform molding, and a test piece (alloy foil) that has a hard feeling but bends without breaking can be preformed. It can be determined that a test piece (alloy foil) that is determined to have toughness and breaks immediately when it is torn or bent is so brittle that it is difficult to form a preform.

  The melting point of the brazing alloy foil is important information for determining the required temperature for brazing. The melting points of the alloy foils of Examples 1 and 2 of the present invention and Comparative Example 2 that can be used as a brazing filler metal are, for example, a test piece (alloy) using a general differential thermal analyzer (DTA: DIFFERENTIAL THERMAL ANALYSIS). The temperature at which a temperature difference occurs between the crucible containing the test piece (alloy foil) and another crucible containing the standard sample during the process of heating and melting the foil in an Ar gas atmosphere (generation point) ) And the temperature at the end (end point) can be measured. In the present invention, the temperature difference generation point and end point are measured by changing the temperature rising rate into three stages of 5 ° C. per minute, 10 ° C. per minute, and 20 ° C. per minute, respectively. When plotting the relationship between the temperature (axis) and the temperature (vertical axis), the intercept of the approximate line (temperature when the rate of temperature rise is zero) based on the origin and end point of the temperature difference is the solidus temperature TS and the liquidus The liquidus temperature TL is defined as the melting point of the test piece (alloy foil).

  Table 2 shows evaluation examples of the alloy foils of Invention Examples 1 and 2 and Comparative Examples 1 and 2 according to the above-described method. In Table 2, the case where the foil structure is substantially amorphous is indicated by “◯”, and Comparative Example 1 in which the production of the alloy foil is difficult is indicated by “X”. Further, regarding the toughness of the foil, “○” indicates that the foil is suitable for preform molding, and “△” indicates the foil that can be preform-molded. Is indicated by “x”. Moreover, regarding the liquidus temperature TL and the solidus phoneme TS, Comparative Example 1 in which it is difficult to produce an alloy foil is indicated by “−”.

  Using the above-described brazing Fe-based alloy foil of the present invention (Example 1 of the present invention), for example, a material to be bonded (base material) such as stainless steel containing Cr contributing to corrosion resistance is brazed, for example, FIG. The brazing joint member 1 of the present invention as shown in FIG. The brazing joint member 1 includes a brazing material layer 3 composed of Fe, 8 to 15% by mass of P, and unavoidable impurities between the first metal material 2a and the second metal material 2b.

  Moreover, the brazing joining member 1 of the present invention has a brazing Fe-based alloy foil such as Example 1 of the present invention disposed between the first metal material 2a and the second metal material 2b. For example, the heat pattern shown in FIG. In the temperature rising process (Z1), the melting point (Tm) of the alloy foil is exceeded and the alloy foil is heated and melted, for example, at a temperature rising rate of 80 ° C. per minute, and in the holding process (Z2), the melting point (TL) is 30 After appropriately holding at a holding temperature (Th) as high as ˜50 ° C., the brazing member 1 is produced by a method of solidifying the molten brazing by cooling at a cooling rate of, for example, 80 ° C. per minute in the temperature lowering process (Z3). be able to. In addition, it is preferable to perform said brazing joining process in a vacuum atmosphere, and formation of the oxide scale on the surface of the brazing joining member 1 can be suppressed.

  Moreover, the brazing joint member 1 of the present invention has a P diffusion region on the brazing material layer 3 side of the first metal material 2a and the second metal material 2b. The diffusion region of P is a form in which P diffuses into the matrix of the material to be joined (base material), and Cr depletion in the brazing joint member when using an alloy foil such as Comparative Example 2 containing conventional B is used. The form of B diffusion that produces a layer is clearly different.

  In the same manner as described above, a brazing joint member having the structure shown in FIG. 1 is produced using a Ni-based alloy foil (Comparative Example 2) containing B and substantially free of P, and the brazing joint member is joined. The structure of the brazing material layer side of the material (base material) can be examined. FIG. 3 shows a brazing joint member 1 (comparative example) having a brazing filler metal layer 3 composed of an alloy foil containing B (comparative example 2) between a first metal material 2a and a second metal material 2b containing Cr. It is a figure which shows typically the section organization of 2). FIG. 4 is a diagram schematically showing an enlarged cross-sectional structure of a part including the first metal material 2a and the brazing material layer 3 of the brazing joint member.

  When a brazing alloy foil containing B is used to braze a metal material containing Cr (first metal material 2a, second metal material 2b), B in the molten brazing by the alloy foil is a metal material containing Cr. It diffuses along the grain boundary of the crystal 2c and combines with Cr in the metal material to produce a Cr boride 2x. When the Cr boride 2x is generated, the Cr concentration is lowered due to the slower diffusion rate of Cr than B, and a Cr-deficient layer 2y having a particularly low Cr concentration is generated around the Cr boride 2x. The metal material (the first metal material 2a and the second metal material 2b) having the Cr-deficient layer 2y from which Cr, which is an important element for enhancing the corrosion resistance, is lost, is based on the Cr-deficient layer 2y existing on the surface thereof. Local corrosion easily occurs.

  In contrast to B described above, P employed in the present invention partially produces Cr phosphide upon diffusion into the metal material, but because the diffusion rate is slower than B, the Cr concentration around Cr phosphide is reduced. I won't let you. Therefore, even if the metal material (the first metal material 2a and the second metal material 2b) has the P diffusion region on the brazing material layer 3 side, it does not have the substantially harmful Cr-deficient layer 2y. Therefore, in the brazing joint member 1 using the Fe-based alloy foil for brazing according to the present invention, since a passive film of Cr is formed in a corrosive environment, it is possible to suppress the occurrence of local corrosion due to its effect.

  The mechanical strength of the brazing joint member 1 is, for example, 0.2% by tensile strength by conducting an evaluation test according to JIS-Z3192 (Tensile and shear test method for brazed joint, No. 2 B test piece). Yield strength, elongation, aperture, etc. can be examined. Moreover, the corrosion resistance of the brazing joint member 1 is, for example, JIS-G0575 (sulfuric acid / copper sulfate corrosion test method of stainless steel, sulfuric acid corrosion solution, butt test piece) or JIS-G0578 (stainless steel ferric chloride corrosion test method, By conducting various corrosion tests according to hydrochloric acid corrosive solution and butt test piece), it is possible to examine the presence and extent of local corrosion in a sulfuric acid environment or a hydrochloric acid environment. A sensitizing heat treatment can also be performed during the corrosion test. The depth of corrosion of the test piece is determined by, for example, preparing a test piece obtained by washing and removing the surface corrosion product with a nylon brush or ultrasonic cleaning and drying the test piece. This can be investigated by measuring with a microscope.

1. Brazing joint member, 2a. 1st metal material, 2b. Second metal material, 2c. Crystal grain, 2x. Cr boride, 2y. 2. Cr-deficient layer; Brazing filler metal layer, Tm. Melting point, Tr. Room temperature, Th. Holding temperature, Z1. Temperature raising process, Z2. Holding process, Z3. Temperature drop process

Claims (5)

  An Fe-based alloy foil for brazing having an amorphous structure composed of Fe, 8 to 15% by mass of P, and unavoidable impurities.   The Fe-based alloy foil for brazing according to claim 1, wherein the P is 12 to 14% by mass.   A brazing joint member having a brazing filler metal layer composed of Fe, 8 to 15% by mass of P, and unavoidable impurities between a first metal material and a second metal material containing Cr.   The brazing joint member according to claim 3, wherein the P is 12 to 14% by mass.   The brazing joint member according to claim 3 or 4, wherein a P diffusion region is provided on the brazing material layer side of the first metal material and the second metal material.