Brazing concept

Abstract

The present invention relates to a blend of at least one phosphorous source and at least one silicon source, wherein silicon and phosphorous together are present in the blend in at least 25 wt %, and wherein the blend is a mechanical blend of powders, wherein each particle in the blend is either a phosphorous source particle or a silicon source particle. The present invention relates further to a composition comprising the blend a substrate applied with the blend, a method for providing a brazed product, and uses.

Claims

1. A mechanical blend of powders for brazing, wherein each particle in the powder of the blend is either a phosphorous source particle or a silicon source particle, wherein silicon and phosphorous together are present in the blend in at least 30 wt %, wherein the at least one silicon source particle is selected from the group consisting of elemental silicon, ferro-silicon, silicon carbides, and silicon borides and the at least one phosphorous source particle is selected from the group consisting of manganese phosphides, nickel phosphides, potassium phosphides, reducible oxygen-containing phosphorus compounds, oxides of phosphorous, hypo-phosphoric acids, pyro-phosphoric acid, and ammonium salts of phosphorus compounds, and wherein the particles in the powder have an average particle size less than 250 m; wherein the blend further comprises powders of a parent material, wherein the parent material is present in an amount less than 75 wt % calculated on the total weight of silicon, phosphorous, and parent material; and wherein the blend has a lower melting point than the parent material.

2. A composition comprising a blend according to claim 1.

3. The composition according to claim 2, wherein the composition further comprises hard particles selected from particles based on oxides, nitrides, carbides, borides, or mixtures thereof, and wherein the hard particles have wear resistance properties.

4. The composition according to claim 2, wherein the composition further comprises powders of a parent material, wherein the parent material is present in an amount less than 75 wt % calculated on the total weight of silicon, phosphorous and parent material.

5. The composition according claim 2, wherein the composition further comprises at least one binder selected from solvents, water, oils, gels, lacquers, varnish, polymers, wax or combinations thereof.

6. The composition according claim 5, wherein the at least one binder is selected from polyesters, polyethylenes, polypropylenes, acrylic polymers, (meth)acrylic polymers, polyvinyl alcohols, polyvinyl acetates, polystyrenes, waxes, or combinations thereof.

7. The composition according to claim 2, wherein the composition is suitable for use as a plating bath.

8. A matrix layered product comprising a substrate and the composition according to claim 2, wherein the substrate is of a parent material which is selected from the group consisting of iron based alloys, nickel based alloys, chromium based alloys, cobalt based alloys, and copper based alloys having a melting point of at least 1000 C.

9. The matrix layered product according to claim 8, wherein the matrix layer is obtained by an electroless plating bath or by an electro plating bath.

10. A braze alloy layered product obtainable by heating a product according to claim 8 to a temperature of at least 900 C., and cooling the product to produce a product having a braze alloy layer on the substrate, wherein said obtained braze alloy layer has a melting point lower than the melting point of the substrate.

11. A coated product obtainable by heating a product according to claim 8 to a brazing temperature less than 1250 C., and cooling the product to produce a coated product, wherein the coated layer has similar melting point as the substrate.

12. The mechanical blend of powders for brazing according to claim 1, wherein silicon and phosphorous together are present in the blend in at least 35 wt %.

13. The mechanical blend of powders for brazing according to claim 1, wherein silicon and phosphorous together are present in the blend in at least 40 wt %.

14. The mechanical blend of powders for brazing according to claim 1, wherein silicon and phosphorous together are present in the blend in 100 wt %.

15. A composition, comprising: the mechanical blend according to claim 14; and at least one binder selected from solvents, water, oils, gels, lacquers, varnish, polymers, wax, or combinations thereof.

16. A method for providing a product having at least one brazed joint between contact areas between substrates, said method comprising the following steps: applying the composition according to claim 2 on at least one substrate; assembling the at least one substrate with at least one additional substrate, wherein the composition according to claim 2 is present in the contact areas; heating the assembled substrates to a brazing temperature below 1250 C., in a furnace in vacuum, in an inert gas, in a reducing atmosphere, or combinations thereof; and cooling the assembled substrates to obtain the product having at least one brazed joint between contact areas of the substrates.

17. A method for manufacturing a braze alloy layered product, which method comprises the following steps: applying a composition according to claim 2 on one substrate; heating the applied substrate to a temperature lower than the solidus temperature of the substrate to obtain a layer of molten phase of braze alloy; and cooling the substrate having the molten phase of braze alloy to obtain a braze alloy layered product, wherein the temperature during heating further is higher than the solidus temperature of the obtained braze alloy.

18. The method according to claim 17, wherein the substrate comprises parent materials selected from parts or plates for heat exchangers, plate reactors, parts of reactors, parts of separators, parts of decanters, parts of pumps, or parts of valves.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is showing a circular pressed plate use in the Examples.

(2) FIG. 2 is showing a graph of Approximation.

(3) FIG. 3 is showing a cross-sectioned metalurgic sample analysed in SEM-EDX

(4) FIG. 4 is showing a cross-sectioned metalurgic sample analysed in SEM-EDX

(5) FIG. 5 is showing a cross-sectioned metalurgic sample analysed in SEM-EDX

(6) FIG. 6 is showing a cross-sectioned metalurgic sample analysed in SEM-EDX

(7) FIG. 7 is showing a cross-sectioned metalurgic sample analysed in SEM-EDX

(8) FIG. 8 is showing a cross-sectioned joint of sample bonded in the vacuum furnace analysed in SEM-EDX

(9) FIG. 9 is showing a cross-sectioned joint of sample bonded in the H2 atmosphere analysed in SEM-EDX

DETAILED DESCRIPTION OF THE DRAWINGS

(10) FIG. 1 is showing a circular pressed plate, which is 42 mm in diameter and 0.4 mm thick, made of stainless steel type 316L. The pressed plate had two pressed beams V and H, each app 20 mm long. Beam V or v stands for left beam and beam H or h stands for right beam, and v and h are used in Example 2.

(11) FIG. 2 shows approximation 1 which is based on a cross section of a brazed test sample. The cross section in FIG. 2 shows the pressed beam in the top of FIG. 2. In the bottom of FIG. 2 is the flat, earlier applied plate. In the capillary between the beam and the flat surface a joint is created. To estimate the amount of braze alloy created in the joint following approximations and calculations have been made. It has been estimated that the volume in the center of the joint is negligible. Therefore, the created braze alloy volume for joints with a width, i.e. width B of 1.21 mm or less, are set to zero. On the outer sides of the beam, i.e. ((XB)/2), formed braze alloy has been accumulated. Thus, the brazing alloy in molted form has been transported by capillary forces to the area of the joint mainly from neighboring areas forming the volumes braze alloy of the triangles.

(12) According to FIG. 2, it is possible to calculate an area by estimate that two triangles are formed on each side of the center of the joint. The angle in the triangle is measured to app. 28. The total measured width is called X and the center width, B. The total area (A) of the two triangles are therefore A=2(((XB)/2)((XB)/2)tan ()))/2, i.e. for FIG. 2 A=2(((X1.21)/2)((X1.21)/2)tan (28)))/2. The total created volume of braze alloy, which had flown to the crevices, would be the area times the length of the two beams. Some of the formed braze alloy does not flow to the crevices and is left on the surface.

(13) FIGS. 3 to 7 shows samples which are cross-sectioned and metalurgical investigated. The cross sections are analysed in SEM-EDX, Scanning electron microscope with energy dispersive spectroscopy. Sample A6 (Mn.sub.3P.sub.2+Si) was exposed to a temperature of 1140 C. for 2 hours, the result is shown in FIG. 3. Sample B6 (Mn.sub.3P.sub.2+Si) was exposed to a temperature of 1140 C. for 2 hours, the result is shown in FIG. 4. Sample NiP was exposed to a temperature of 1120 C. for 2 hours, the result is shown in FIG. 5. Sample (NiP+Si) was exposed to a temperature of 1120 C. for 2 hours, the result is shown in FIG. 6. Sample Mn.sub.3P.sub.2 was exposed to a temperature of 1120 C. for 2 hours, the result is shown in FIG. 7.

EXAMPLES

(14) The tests in these Examples were made to investigate if silicon, Si, is able to create a braze alloy when applied on the surface of a test sample of base metal. Also different amounts of phosphorous, P, were added since phosphorous also can decrease the melting point for braze alloys. Properties of the tested blends were also investigated. In the Examples wt % is percent by weight and atm % is percent of atoms.

(15) If nothing else is stated the test samples of parent metal for all tests were cleaned by dish washing and with acetone before samples of the blends of silicon and phosphorous source were added to the test samples.

Example 1

Measure of Binder (Polymeric and Solvent) Content in the S-20 Binder

(16) Also the content of dry material within the S-20 binder was tested. The sample of S-20 binder was Nicrobraz from Wall Colmonoy. The test sample was weighted and thereafter the sample of the wet binder were dried in room temperature for 24 h. The results can be found in Table 2.

(17) TABLE-US-00002 TABLE 2 Weight Dry Clean Plate with Plate with Weight dry weight plate wet binder dry binder wet binder binder of binder Sample [g] [g] [g] [g] [g] [wt %] S20 4.36 4.92 4.38 0.56 0.02 3.57 binder

Examples 2

(18) Two different blends were used in Example 1. The blends were Mn.sub.3P.sub.2 together with Si, see Table 3. The blends were tested as melting point depressants.

(19) TABLE-US-00003 TABLE 3 Sum Si + S20 Total Si Mn.sub.3P.sub.2 Mn.sub.3P.sub.2 (Mn.sub.3P.sub.2):(Si) wet weight Blend [g] [g] [g] [g]/[g] [g] [g] A 4.07 10.0 14.07 2.46:1 16.80 30.87 B 6.15 10.0 16.15 1.63:1 15.98 32.13

(20) Circular test pieces of type 316 stainless steel, diameter 42 mm were applied with the blends. On each test piece (test piece+blend) was a pressed waffle of type 254 SMO was placed. The samples were heat treated for app 2 h in full vacuum at different temperatures for each test. Different amounts of the two blends were used in the tests.

(21) Test samples A1, A2, A3, B1, B2, and B3 were heat treated for app 2 h in full vacuum at 1120 C. Test samples A4, A5, A6, B4, B5, and B6 were heat treated for app 2 h in full vacuum at 1140 C.

(22) TABLE-US-00004 TABLE 4 Applied Blend + Dry Temperature Binder Blend [ C.] [g] A1 1120 C. 0.22 A2 1120 C. 0.13 A3 1120 C. 0.14 A4 1140 C. 0.33 A5 1140 C. 0.10 A6 1140 C. 0.16 B1 1120 C. 0.19 B2 1120 C. 0.09 B3 1120 C. 0.16 B4 1140 C. 0.16 B5 1140 C. 0.34 B6 1140 C. 0.14

(23) The width of the created joints were measured as a function of applied amount, blend and heat treating temperature, see FIG. 2. The calculated width are summerised in Table 5.

(24) TABLE-US-00005 TABLE 5 Width of Joint Width of Joint Blend on Waffel Triangle 1 Triangle 2 Sample [g] [m] [m] A1 0.22 2961 3050 A2 0.13 1640 1610 A3 0.14 2070 2240 B1 0.19 2170 2290 B2 0.09 1240 1220 B3 0.16 2010 1600 A4 0.33 3107 2993 A5 0.10 1832 1810 A6 0.16 2195 2202 B4 0.16 1833 1811 B5 0.34 3264 3238 B6 0.14 1470 1662

(25) The samples were cross-sectioned and metalurgical investigated. The cross sections were analysed in SEM-EDX (Scanning electron microscope with energy dispersive spectroscopy). The investigations shows that the main part of the composition of the joint is a blend of the two parent material used, i.e. 316 and SMO. For the analysed samples the major part of the composition in the joints origin from the parent materials.

(26) Approximate values for the elements of 316 and SMO are summarized in Table 6.

(27) TABLE-US-00006 TABLE 6 316 SMO Element [wt %] [wt %] C 0.03 max 0.02 max Si 1.0 max 0.8 max P 0.045 max 0.030 max Cr 16.5-18.5 19.5-20.5 Mn 2.00 max 1.0 max Fe Balance (~65) Balance (~53) Ni 10.0-13.0 17.5-18.5 Mo 2.0-2.5 6.0-6.5 Cu 0.5-1.0 Total 100.00 100.00

(28) The analysed joint of test sample A6 is shown in Table 7, see also FIG. 3.

(29) TABLE-US-00007 TABLE 7 Spectrum 1 Spectrum 2 Spectrum 3 Element [wt %] [wt %] [wt %] C 3.04 2.86 2.95 Si 0.40 2.40 1.52 P 1.43 0.76 Cr 16.11 18.00 17.33 Mn 1.50 1.63 1.35 Fe 62.90 50.54 51.15 Ni 13.88 18.00 20.76 Mo 2.17 5.16 4.17 Total 100.00 100.00 100.00

(30) The analysed joint of test sample B6 is shown in Table 8, see also FIG. 4.

(31) TABLE-US-00008 TABLE 8 Spectrum 1 Spectrum 2 Spectrum 3 Element [wt %] [wt %] [wt %] C 2.87 2.86 2.77 Si 0.43 2.58 0.42 P 0.17 1.76 Cr 18.75 16.72 16.61 Mn 2.41 1.46 Fe 50.56 50.18 16.61 Ni 21.70 18.90 13.63 Mo 5.53 4.58 1.91 Total 100.00 100.00 100.00

Example 3

(32) Example 3 circular test pieces of type 316 stainless steel, diameter 42 mm were applied with NiP plated 316, and NiP plated 316 together with a layer of Si on top of the NiP plated layer. A pressed waffle of type 254 SMO were placed on top of each sample. The test pieces were heat treated for app 2 h in full vacuum at 1120 C. The analysed joint of test sample NiP plated 316 is shown in Table 9, see also FIG. 5. The thickness of NiP is 50 m.

(33) TABLE-US-00009 TABLE 9 Spectr. Spectr. Spectr. Spectr. 5 6 Spectr. 7 8 Spectr. 9 10 Element [wt %] [wt %] [wt %] [wt %] [wt %] [wt %] O 1.48 0.67 1.20 0.99 2.34 0.91 Si 0.26 0.29 0.18 0.32 P 9.60 0.95 14.41 1.06 10.84 1.07 Cr 8.83 7.64 17.99 7.78 13.27 7.42 Mn 0.61 0.51 0.43 Fe 23.11 33.69 20.17 33.60 23.03 33.22 Ni 54.25 55.61 40.95 55.06 46.83 56.01 Mo 1.86 1.16 4.77 1.33 3.25 1.06 Total 100.00 100.00 100.00 100.00 100.00 100.00

(34) The result in Table 9 shows that the joint mainly consists of NiP, and NiP has not alloyed properly with the parent materials 316 and SMO.

(35) The analysed joint of test sample NiP plated 316 together with a layer of Si is shown in Table 10, see also FIG. 6. The thickness of NiP is 50 m.

(36) TABLE-US-00010 TABLE 10 Spectrum 11 Spectrum 12 Spectrum 13 Element [wt %] [wt %] [wt %] C 7.44 6.41 6.34 O 1.48 1.71 1.06 Si 2.22 1.99 2.43 P 5.76 8.83 0.48 Cr 11.13 12.33 9.47 Mn 0.39 0.51 0.00 Fe 30.33 26.57 38.80 Ni 38.70 38.19 40.10 Mo 2.54 3.46 1.33 Total 100.00 100.00 100.00

(37) The results summarized in Table 10 show increased values of Fe in the joint, this means that the addition of Si supports the alloying process during the heating step. Thus the elements of the joint have increased similarity to the two parent materials which are joined.

Example 4

(38) In Example 4 circular test pieces of type 316 stainless steel, diameter 42 mm were applied with Mn.sub.3P.sub.2. A pressed waffle of type 254 SMO were placed on top of the applied 316 test piece. The test pieces were heat treated for app 2 h in full vacuum at 1120 C. The results summarized in Table 11.

(39) TABLE-US-00011 TABLE 11 Spectrum 2 Spectrum 3 Spectrum 4 Element [wt %] [wt %] [wt %] C 6.14 7.68 4.76 O 1.39 1.24 1.26 Si 2.22 3.17 2.72 P 2.03 2.13 0.978 Cr 18.51 20.23 16.44 Mn 1.52 1.63 2.04 Fe 48.37 42.97 53.22 Ni 48.37 42.97 53.22 Mo 6.36 11.55 3.05 Total 100.00 100.00 100.00

(40) Table 11 shows that the created joint contains increased values of Fe origin from the parent materials.

Example 5

(41) In Example 5 joining tests were performed. Pressed heat exchanger plates made of type 316 steel app 0.4 mm thick, and an area of app 19070 mm, was applied on the top surface with Mn.sub.3P.sub.2 and Si as the phosphorous source and the silicon source, i.e. the melting point depressants (MPD).

BACKGROUND

(42) The hypothesis was to have MPD on the surface, the MPD would diffuse is to the surface of the parent material creating an alloy. This alloy would then have a lower melting point then the parent material. If the composition of the alloy was right the alloy would both melt and flow by capillary forces to for example contact points between the pressed plates in the heat exchanger. To succeed the joints need to meet the following three criteria:

(43) 1) Substantial size and form of the materials to be joined, so that the joint can be loaded.

(44) 2) The composition of the joint should also be more similar to the parent material, therefore having mainly the properties of the parent material and not of the melting point depressants properties. The opposite is if the composition of the joint would be mainly formed by the applied material the method would instead be soldering or brazing, and therefore also mainly having the material applied properties.

(45) 3) The joint also needs to be wet onto the material to be joined with a contact angle less than 90.

(46) To obtain these three criteria the MPD needs to be dissolved and diffuse into the top layer of the plate without being consumed by reactions, evaporated or diffusion to rapidly into the base material so that no melt is formed. The alloy that is formed must have a viscosity that enables flowing of the melt at the joining temperature. The melt can only be formed if the amount of MPD is high enough in the parent material to create a melt at the joining temperature. The melt that is formed must have the properties to wet the material to be joined. The right amount and ration of the MPD must be applied.

Mixing and Applying of the Blend of MPD

(47) 102.56 gram of Mn.sub.3P.sub.2, type 99% pure powder100 mesh from Advanced Chemicals and 33.92 g of Si gram of crystalline silicon powder particle size 325 mesh, 99.5% (metal basis) 7440-21-3 from Alfa AesarJohnsson Matthey Company was mixed together with 50.28 g of binder S20 gel from Wall Colmonoy, (Please observe that the Mn.sub.3P.sub.2 is a mixture of different forms of MnP).

(48) The plates were taken from the pressing tool after pressing. The plates were not degreased or cleaned before applying the blend of MPD. The blend of MPD together with the binder was applied on the pressed plate's top surfaces by using a hand roller (normally used when painting). A quit large amount of filler was applied on each plate app 3-5 g/plate.

Heat Treatment Cycles

(49) The heat treatment was carried out in a Hydrogen Furnace (HF), i.e. a Furnace cycle 1 in a belt furnace in hydrogen atmosphere. Bonding temperature app. 1115 C., belt speed 65 mm/min. Total length of the belt furnace approximately 5000 mm, meaning that the total time in the furnace was approximately 80 min.

(50) Furnace cycle 2 was carried out in a Vacuum Furnace (VF), i.e. in a batch furnace in vacuum atmosphere. Bonding temperature approximately 1120 C. for approximately 1 h. The total time in the furnace was approximately 4 h.

Results

(51) The bonded heat exchanger plates from each cycle was cut, ground, polished and then evaluated optically and by SEM-EDX (Scanning electron microscope with energy dispersive spectroscopy).

Optical Analysis

(52) Large joints with a smooth surface was observed, this very beneficial for braze joints see FIG. 8 and FIG. 9. The formed alloy had wetted the other material that was joined and the wetting angle was less than 90.

(53) There were some holes in the plate that were bonded in the vacuum furnace indicating that a too large amount of MPD was applied on those spots, also indicating that a larger amount of melted phase was formed in the 4 h vacuum process than in the app 1 h hydrogen process.

SEM-EDX Analysis

(54) The analyzed area for the sample joined in the vacuum cycle is shown in FIG. 8 and for the hydrogen atmosphere in FIG. 9. The analyzed results for the VF (vacuum furnace) is presented in Table 12 and for the HF (hydrogen furnace) in Table 13, all results are percent by weight % (wt %). Areas representing the pure joint, areas with both the joint and the parent material and the pure parent material are presented in the results.

(55) TABLE-US-00012 TABLE 12 Table 12, SEM-EDX analysis of the compositions for a joint made in Vacuum Furnace. Samples of VF Composition* app 80% of the joint and app 20% Composition Composition Composition of the parent of the parent of the joint of the joint material material Spectrum 1 Spectrum 3 Spectrum 4 Spectrum 2 Elements [wt %] [wt %] [wt %] [wt %] Fe 47.8 45.6 52.3 63.8 Cr 16.6 15.8 15.8 16.7 Ni 14.0 14.1 14.3 14.3 Mn 9.1 9.6 7.7 1.5 P 6.4 6.9 4.5 0.3 Mo 3.1 3.1 2.5 1.9 Si 3.0 2.8 2.9 0.7 Other 2.0 1.0 Total 100 100 100 100 *For some analyses a part of the parent material is also part of the analyzed result, this was estimated in form as wt %.

(56) TABLE-US-00013 TABLE 13 Table 13, SEM-EDX analysis of the compositions for a joint made in Hydrogen Furnace. Samples of HF Composition* app 80% of the joint and app 20% Composition Composition Composition of the parent of the parent of the joint of the joint material material Spectrum 1 Spectrum 3 Spectrum 4 Spectrum 2 Elements [wt %] [wt %] [wt %] [wt %] Fe 45.9 49.0 49.8 65.6 Cr 14.5 14.7 14.8 16.6 Ni 13.9 14.1 12.7 14.0 Mn 13.1 12.7 10.9 1.4 P 7.6 4.9 4.8 Mo 2.0 0.9 1.8 2.0 Si 3.0 3.7 3.5 0.5 Other 1.8 Total 100 100 100 100 *For some analyses a part of the parent material is also part of the analyzed result, this was estimated in form as wt %.

SUMMARY AND CONCLUSIONS

(57) The investigation showed that it was possible to create a melted alloy of the parent material by using a Mn.sub.3P.sub.2 and Si as MPD on the plate surface. It was also shown that the composition of the formed alloy in the joint after cooling had a composition similar to the base material. It was also shown that the smooth and large joints were formed that had wetted the other surface with a contact angle less than 90. It was also shown that it was possible to obtain the result in both a hydrogen atmosphere and under vacuum.