JPWO2014084242A1 - Low melting point brazing material - Google Patents

Abstract

The present invention provides a low melting point and easy to use brazing material. The low melting point brazing material of the present invention is composed of Cu 0.3 to 41.4 wt%, Ni 0.04 to 2 wt%, and the balance Sn. The preferable content of Cu is 7.6 to 41.4% by weight. Further, Al may be added in an amount of 0.006 to 0.1% by weight, and Ge may be added in an amount of 0.001 to 1% by weight.

Description

  The present invention relates to a low-melting-point brazing material containing Sn as a main metal, and is particularly useful as a brazing material for joining metal pipes together.

  A variety of brazing materials are known. These brazing materials have alloy compositions such as silver brazing using Ag as a main metal, copper brazing using copper and zinc, brass brazing, and aluminum brazing using aluminum. However, since the brazing material generally has a high melting point, a large amount of heat energy is required for the brazing operation for joining the metals together. And current technology requires a large amount of power to obtain thermal energy.

  By the way, since the conventionally known brazing material is generally a high melting point alloy, thermal energy is also applied to the joined material during the joining operation, and it is similarly exposed to a high temperature atmosphere. In general, copper pipes are designed with a thickness that assumes annealing due to thermal energy at the time of joining, so if more heat energy is applied than necessary, further annealing occurs, reducing the strength of the copper pipe itself. End up. In addition, when an oxide is present on the metal surface that is a bonded product, it is reduced, but the surface is oxidized again in a short time and the surface roughness becomes rough. For example, when a copper pipe used in a water heater that allows water to flow inside is joined at a high temperature, if the inside of the pipe is oxidized, the inner surface becomes rough, and the oxide inside the pipe accumulates in the pipe. There is a problem that the fluid resistance increases. Therefore, it is preferable to join at as low a temperature as possible so that a redox phenomenon does not occur on the surface of some joints.

  On the other hand, since a relatively large physical force often acts on the joint joined by brazing, it is important to ensure the joining strength. And in order to attach importance to guaranteeing the strength of the joined joint, it is a fact that hard solder is widely used after recognizing that there is the above-mentioned problem.

JP 2009-061475 A JP 2001-049368 A Japanese Patent Laid-Open No. 06-007921

  Patent Document 1 relates to a brazing material having a low melting point, but contains about 50% by weight of Ag, and is a kind of silver brazing where the cost of the brazing material is very high.

  Patent Document 2 has a relatively high tin content, but is a kind of copper solder containing 70% by weight or more of copper as a main metal and is an alloy having a high melting point.

  Patent Document 3 is composed of a high-temperature solder and contains 30% by weight or less of tin, but contains a large amount of lead.

  By the way, brazed joints are used for various purposes. For example, a copper pipe provided inside a hot water heater raises the temperature with a burner while water passes through the hot water dispenser and discharges it from a hot water nozzle. It is a structure to do. In the copper pipe, straight pipes are sequentially connected in a meandering manner with a bent pipe, and a brazing material is used for a connection portion between the bent pipe and the straight pipe. In this structure, the portion heated by the burner is usually a straight pipe, and the bent pipe and the joint portion of the straight pipe are not heated. Then, since the temperature of the joint portion is at most about 150 ° C., a heat resistant temperature of about 800 ° C. like a known silver solder is not necessary.

  Therefore, the inventor pays attention to this point, and even if the alloy has a low melting point, when a pipe is used as a flow path of water boiling at 100 ° C., such as a water heater, a solid temperature of 200 ° C. or higher is used. After confirming that it could function as a brazing filler metal at the phase wire temperature, we developed an alloy that has a low melting point and is easy to use. In addition, the alloy composition which does not contain lead, which is considered harmful as in Patent Document 3, is assumed.

  In order to achieve the above object, the present invention has developed a low melting point brazing material comprising 0.3 to 41.4% by weight of Cu, 0.04 to 2% by weight of Ni and the balance Sn. Sn and Cu are eutectic at 0.7 wt% Cu in the phase diagram, and their melting point is about 232 ° C. And since Ni is added to Sn-Cu, solidus temperature rises from eutectic temperature. Then, if it is Sn-Cu-Ni alloy of this range, even if it uses as a brazing material for connecting the pipe provided in the inside of a water heater, the joint part joined by the brazing material is exposed to the flame of a burner. Otherwise, the temperature will not exceed the solidus temperature. Therefore, even with the composition of the present invention, there is no accident that the brazing material constituting the joint melts and the joint joint comes off.

  A more preferable alloy of the present invention is that the Cu content is 7.6% by weight or more. When 7.6 wt% of Cu is contained in Sn, the solidus temperature is 227 ° C. and the liquidus temperature is 415 ° C., and the solid-liquid coexistence state exists in the temperature range therebetween. When Cu is contained at 41.4% by weight, the liquidus temperature is 640 ° C. As a result, if joint production is started in a liquid state that exceeds the liquidus temperature at the time of joint production, the state of solid-liquid coexistence will continue for a long time until the temperature falls to the solidus temperature at which it is completely solidified. The pipe joint has a low flowability and a large temperature distribution at the time of joining.

Furthermore, a low melting point brazing material in which 0.006 to 0.1% by weight of Al was further added to the above composition was used. When the Cu content is up to 7.6% by weight, the primary crystal Cu ₆ Sn ₅ intermetallic compound is a needle-like crystal, which impedes fluidity and permeates into the gap between the straight pipe and the bent pipe. Can be a hindrance factor. However, by adding a small amount of Al, Al becomes a nucleus, and the growth rate of the Cu ₆ Sn ₅ intermetallic compound is slowed down to change to a particulate crystal. That is, the Cu ₆ Sn ₅ intermetallic compound does not grow in a dendritic shape, thereby preventing fluidity inhibition. Al is chemically very easy to oxidize and changes to an oxide called Al ₂ O _3. However, in the present invention, the addition of a small amount of Al means that the Cu ₆ Sn ₅ intermetallic compound grows in a long dendritic crystal. It is expected to function as a nucleus for suppressing, and the additive substance may be Al ₂ O ₃ . That is, Al to be added in the present invention does not need to be in a pure state, and may be in a state in which Al ₂ O ₃ is mixed, so that it is not necessary to handle it strictly. That is, it is possible to replace part or all of the added Al with Al ₂ O ₃ . Incidentally, Cu ₆ added amount of Cu is in the case of more than 7.6% by weight, have been known to produce also Cu 3 _Sn intermetallic compound, the total amount of the intermetallic compound since no increase or decrease, the remaining The needle-like formation of Sn ₅ intermetallic compound crystals can be inhibited by adding Al, and fluidity can be ensured.

Note that the addition of Ni, if added Ni against Sn-Cu, substituted partly to Ni of Cu of _Cu 6 Sn ₅ intermetallic compound, (Cu, _Ni) to 6 Sn ₅ intermetallic compound Become. The appearance of the (Cu, Ni) ₆ Sn ₅ intermetallic compound is different from that of Cu ₆ Sn ₅ and has a more rounded shape. Therefore, by adding Ni in addition to the addition of Al, the generation ratio of the Cu ₆ Sn ₅ intermetallic compound having a needle-like structure can be reduced, and the molten brazing material can be infiltrated into a narrow gap. . Then, the content thereof, Cu is in the case of 0.3 wt%, it is preferable that the Ni is contained about 0.04 wt% to suppress the formation of _Cu 6 Sn ₅ intermetallic compound, and Cu The solidus temperature when the upper limit of 41.4% by weight is 640 ° C., and the Ni content in the Sn—Ni phase diagram at about 600 ° C. is approximately 2% by weight corresponding to this. Therefore, the range was limited.

In the present invention, 0.001 to 1% by weight of Ge may be added to the above alloy composition. In particular, Ge exerts a function of refining the state of the Cu ₆ Sn ₅ intermetallic compound, and thus contributes to penetration into a narrow gap as a brazing material. Regarding the addition amount of Ge, even when the lower limit value was 0.001% by weight, it was confirmed that the function of refining the state of the Cu ₆ Sn ₅ intermetallic compound was exhibited, and added exceeding 1% by weight. Even so, since Ge is a relatively light metal, the surplus that does not contribute to the miniaturization of intermetallic compounds only floats on the surface of the molten metal, so there is no technical significance in adding more than this amount. Because.

  In addition to Ge, 1 or 2 of a metal group consisting of Zn, Sb, Bi, P, Se, Ga, Ag, In, Pd, Fe, Ti, Au, Co, Cr, Mo, Mn, V, and Cs The above metals may be further added in an amount of 0.001 to 1% by weight. It is known that these metals do not contain Pb and can be expected to have an effect of further improving the joint strength by adding a small amount to a solder alloy containing Sn as a main metal. Also in the present invention, excellent fluidity, oxidation resistance, good hardness improvement, etc. are not excluded, and in this sense, these trace added metals are included.

  The low melting point brazing material of the present invention can be used effectively when the temperature in the vicinity of the joint does not exceed about 200 ° C. during use of the equipment, and since the fluidity is high in the liquid state, the joints have a narrow interval. However, it is possible to sufficiently wrap the brazing material. Therefore, a joint having a large joining area and high strength can be formed. In addition, if the Cu content is increased, the liquidus temperature will rise, and as a result, the state of solid-liquid coexistence will continue for a long time. Around is obtained. Therefore, with the composition of the present invention, the brazing material can be reliably applied to the joint portion of the joint, and a highly reliable joint joint can be obtained.

It is the schematic which showed the procedure which joins copper pipes of a straight pipe with a bending pipe | tube using the brazing material of this invention. It is the schematic which showed the test piece for confirming the shear strength of the brazing material of the Example of this invention, and the brazing material of a comparative example.

  Hereinafter, preferred embodiments of the present invention will be described according to examples. FIG. 1 shows an initial process when straight pipes are joined with a bent pipe using a brazing material. The process proceeds from a to d in the figure. In the figure, reference numerals 1 and 1 denote copper pipes used in the water heater, and the joint portion 1a has a diameter that has been expanded in advance. Reference numeral 2 denotes the same copper bent pipe, and the respective tip portions are inserted into the diameter-expanded end portion of the straight pipe 1 to form joint portions. 3 is a brazing material heated to a molten state, and the brazing material 3 is filled in the melting tank 4. A specific process inserts the bending pipe 2 with respect to the straight pipes 1 and 1 like FIG. In addition, a flux is previously applied to the overlapping portion. Then, with the bent pipe 2 inserted into the straight pipes 1 and 1, the tip ends of the straight pipes 1 and 1 are immersed in the molten brazing material 3 (FIG. 1c) and then pulled up (FIG. 1d). Slowly cool the material to solidify. Then, the brazing material remains at the location where the flux is applied, and the joint portion 5 is completed. Note that FIG. 1 is a schematic diagram of the apparatus used for the test. In actual operation, a linear brazing material is wound around the joint in place of the means for dipping using the melting tank 4. Then, a means for melting by heating is adopted. However, in the present invention, the configuration itself in which the brazing material is provided in the vicinity of the joint is not important, so that currently known means can be widely adopted.

  According to the schematic diagram shown in FIG. 1, the brazing material of the present invention as shown in Table 1 is prepared as samples 1 and 4, and the brazing material of the comparative example is prepared as samples 2 and 3, and the joints using the respective brazing materials are prepared. A pressure test was conducted.

Each of these samples is a tin brazing material containing Sn as a main metal.

  First, Table 2 shows the results of holding the load pressure at 20 MPa for 20 seconds as the initial pressure resistance test. The load was applied in an atmosphere at room temperature of 20 to 23 ° C.

  As a result, it was confirmed that any brazing material using any sample can withstand a load of about 20 MPa for a short time immediately after manufacture of the joint.

  Next, considering the actual use as equipment, Table 3 shows the results of exposing the joint at 120 ° C. for 500 hours and then applying a load of 20 MPa.

  As a result, the 3.5Ag-Sn brazing material of Sample 2 was broken at the joint interface, and water leakage occurred when the pressure exceeded 17 MPa. Sn and Ag are eutectic at 3.5% by weight of Ag, and their melting point is 221 ° C., so there is no problem with the melting temperature of the alloy, but it is assumed that a sufficient bonding area could not be secured. Is done.

  Further, Table 4 shows the results of exposing the joint at 150 ° C. for 500 hours and then increasing the load pressure to 20 MPa. The difference from the test in Table 3 is that the exposure temperature was increased by 30 ° C.

As a result, the fracture of the interface for Sample 3 was the same as in the test of Table 3, but the pressure at which water leakage occurred was further reduced, and leakage occurred when the pressure exceeded 10 MPa.
As a conclusion of Table 3 and Table 4, it was confirmed that the possibility of using Sample 2 as a low melting point brazing material was extremely low.

  Subsequently, as a more severe test, a salt spray test (SST) was performed on all samples. As test conditions, a sodium chloride aqueous solution was prepared at a salt water concentration of 50 g / L, sprayed continuously at 1.3 mL / hour for 120 hours, and then a pressure resistance test was performed under the conditions (room temperature) shown in Table 2. The results are shown in Table 5. The salt water sample was sprayed at an inclination angle of 30 degrees. In addition, about the sample 2, since it was judged that it was nonconformity by the previous test, the test was not implemented.

  As a result, Samples 1, 3, and 4 showed good pressure resistance.

  As a result of the test, there were no problems with Samples 1 and 4 that are within the scope of the present invention and Sample 3 that was a comparative example. However, Sample 3 shown as a comparative example is a tin-lead eutectic alloy of Sn-37 wt% Pb, and its melting point is 183 ° C., which is lower than the set lower limit temperature 200 ° C. predicted by the present invention. Therefore, when actually used in a hot water heater, there is a risk that the alloy itself will melt, so that a brazing material having this composition cannot be employed.

  Each alloy sample was melted at a temperature about 50 ° C. higher than the melting point of each alloy in the small melting tank 4 of FIG. 1, and the dip time for manufacturing the joint was 10 seconds. Was made.

Next, in order to confirm the shear strength of the joint, a joint was provided at the portion where the copper plates were overlapped, and a shear test was performed. FIG. 2 is a schematic view of a sample piece prepared for the test. 10 · 10 is a copper plate having a thickness of 1 mm, a width of 5 mm and a length of 25 mm, 11 is a brazing material having a width of 5 mm and a length of 5 mm, and an area of 25 mm ^2. This constitutes a lap joint. The apparatus used for the shear test was a universal tester AGIS-10 kN manufactured by Shimadzu Corporation, and pulled at a speed of 1 mm / min in a room temperature (20-23 ° C.) atmosphere. The test piece was produced by brazing the joint alloy to a copper plate and stacking the two together. The alloy used was 0.04 g, and an optimum flux was used in consideration of the bonding temperature range. The brazing temperature is set 50 ° C. higher than the liquidus temperature. For Examples 4, 5, 6, 10, and 11, the electric furnace is used and the other test pieces are heated on a hot plate to confirm melting of the brazing material. And held for 30 seconds. And the test piece created by this method was heated for 2 minutes on a hot plate adjusted to 460 ° C. to obtain an aging sample.

  The composition of the test piece used for the shear test is as follows.

  Table 7 shows the shear stress of each test piece shown in Table 6 and the determination as to whether or not it can be adopted. As a result, a shearing force was applied to the test piece, the stress was measured before and after the time when shearing occurred in the joint portion, and the ratio before and after shearing was expressed as a percentage as a change rate. Then, the case where the rate of change was 60% or more was judged as “good”, and the case where it was less than 60% was judged as “bad”. The inventor recognizes from knowledge that even if the rate of change is about 50%, there is sufficient strength during normal use. However, considering the long-term use in actual use, a more strict standard is used. % Was set. As for the temperature condition, the strength of the joint deteriorates due to the heat cycle applied to the joint joint, so if the test is performed only under the temperature condition assuming actual use, it can cope with deterioration with time. Since there is a possibility that it cannot be performed, a test piece aged at 460 ° C. higher than the assumed actual use temperature was used.

  From the results shown in Table 7, as in Examples 1 to 12, it was possible to determine that all of the additive elements of Cu, Ni, Al, and Ge were good within the upper and lower limits of the present invention. Furthermore, as in Examples 13 to 20, the composition obtained by adding a small amount (0.010% by weight) of Zn, Sb, P, Ga, Ag, Ti, Co, or Mn to the composition of Example 8 is good. Results were obtained. It should be noted that the same results were obtained even when Bi, Se, In, Pd, Fe, and Au, which are other elements described in claim 6, were added in the same degree as in Examples 13 to 20. You can expect to get. Furthermore, even with a composition comprising Sn—Cu—Ni, sufficiently good results could be obtained as shown in Examples 21-24.

DESCRIPTION OF SYMBOLS 1 Straight pipe 2 Curved pipe 3 Molten brazing material 4 Melting tank 5 Joint part 10 Copper plate 11 Lap joint

Claims (6)

A low melting point brazing material comprising Cu 0.3 to 41.4 wt%, Ni 0.04 to 2 wt% and the balance Sn. The low melting point brazing material according to claim 1, wherein Cu is preferably 7.6 to 41.4% by weight. The low melting point brazing material according to claim 1 or 2, further comprising 0.006 to 0.1% by weight of Al. The low melting point brazing material according to claim ₃ , wherein a part or all of Al is replaced with Al ₂ O ₃ . The low melting point brazing material according to any one of claims 1 to 4, further comprising 0.001 to 1% by weight of Ge. In addition to Ge, one or more metals selected from the group consisting of Zn, Sb, Bi, P, Se, Ga, Ag, In, Pd, Fe, Ti, Au, Co, Cr, Mo, Mn, V, and Cs The low melting point brazing material according to claim 5, wherein 0.001 to 1 wt% is added.

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