EP1996361A2

EP1996361A2 - Method for soldering components

Info

Publication number: EP1996361A2
Application number: EP07711525A
Authority: EP
Inventors: Bradley Davis Abell; Klaus Dieter FÖRSTER; Bernd GRÜNENWALD; Andreas Jenseit; Cord Völker
Original assignee: Behr GmbH and Co KG
Current assignee: Mahle Behr GmbH and Co KG
Priority date: 2006-02-13
Filing date: 2007-02-13
Publication date: 2008-12-03
Also published as: US20090026248A1; WO2007093388A2; US8196804B2; BRPI0707770A2; WO2007093388A3

Abstract

The invention relates to a method for soldering components, in particular heat exchangers, in particular made of aluminium materials, aluminium alloys or wrought alloys, in a soldering furnace, in particular a continuous soldering furnace or a batch-type soldering furnace, which comprises a muffle, which is flushed with protective gas in order to create a protective atmosphere. In order to make the production of soldered components easier, during the soldering of the components the muffle is supplied with such a greatly increased amount of gas, in particular protective gas or reaction gas, that a low-oxygen protective atmosphere is created.

Description

Method for soldering components

The invention relates to a method for soldering components, in particular of heat exchangers, in particular made of aluminum materials, aluminum alloys or wrought alloys, in a soldering oven, in particular a continuous soldering oven or a batch-type solder oven, which comprises a muffle, which is purged with inert gas to a To create a protective gas atmosphere.

The brazing of aluminum heat exchangers is carried out in so-called protective gas flow furnaces with flux. In the area of the oven muffle, the furnace atmosphere between an inlet opening and an outlet opening has an oxygen content of approximately 500 ppm in the inlet area and approximately 40 ppm in the so-called soldering area. With such an oxygen content in the furnace atmosphere, flux-free soldering is hardly or not possible. Fluxes are non-metallic substances that melt before reaching the melting temperature of the solder and wet the surface to be soldered. As a result, an oxide layer forming on the surface of aluminum and the oxygen atmosphere is dissolved or washed away. The flux simultaneously prevents a new oxidation of the surface by residual oxygen present in the furnace atmosphere. Known soldering methods with flux are the Nocolok method and the CAB (Controlled Atmosphere Brazing) soldering method. The application of the flux is complicated and cost-intensive. In addition, the components are after The flux is applied to the soldering, which applies a complex cleaning process, in particular when using chloride fluxes. Other drawbacks of flux killing include: flux cost, air receiver investment and operating costs, waste disposal, dust and environmental impact, post-drying drying / heating of components, energy consumption, dry kiln investment and operating costs, space requirements, flux on the surface of the workpieces, flux residues in the medium cycle. European Patent EP 0 781 623 B1 discloses a method for the production of brazed aluminum heat exchangers in which special heat exchangers in CAB brazing furnaces are partially soldered without flux.

It is also possible to solder the aluminum heat exchangers in single or multi-chamber vacuum furnaces under vacuum. The rupture of the existing oxide skin is due to the different thermal expansion of alumina and pure metal, as well as the evaporation of magnesium from solder and base material at high temperatures. By evacuating the recipient, oxygen is kept away from the parts to be soldered. This low oxygen concentration in the furnace system prevents the exposed surface of the base materials and the surface of the molten solder from being coated again with an oxide skin during soldering. For soldering in a vacuum, however, technically complex and therefore expensive soldering systems are required. Furthermore, the parts to be soldered must be absolutely clean, which can only be ensured by a cost-intensive pretreatment. Other disadvantages of vacuum brazing are the high maintenance and repair costs as well as the high demands on the surface quality and the accuracy of fit of the components.

The object of the invention is to provide a method by which the production of soldered components, in particular of heat exchangers, in particular of aluminum materials, aluminum alloys or wrought alloys, in a brazing furnace, in particular a continuous brazing furnace or a batch-type brazing furnace comprising a muffle , which is purged with inert gas to create a protective gas atmosphere, is simplified. The object is in a method for soldering components, in particular heat exchangers, in particular made of aluminum materials, aluminum alloys or wrought alloys, in a soldering oven, in particular a continuous soldering oven or a batch-type solder oven, which comprises a muffle, which is purged with inert gas to To create a protective gas atmosphere, achieved in that the brazing furnace muffle during soldering of the components such an excessive amount of gas, in particular inert gas or reaction gas is supplied, that a low-oxygen inert gas atmosphere is created. By supplying the greatly increased amount of inert gas, the protective gas atmosphere is improved so that the components can be soldered without the addition of flux. The process of the invention is preferably used in so-called inert gas continuous furnaces. The invention may, but need not, completely eliminate the use of flux. A partial addition of flux on or to the component is possible and has no negative impact on areas of the component that are soldered fluxless.

In vacuum soldering, the required high vacuum for the vacuum furnace systems requires a very high technical outlay. Therefore, vacuum furnace systems are very expensive to procure and expensive in operations. Also on the purity of the surface of the components to be soldered contamination (dirt, dust, chips, oxide layers, residues and traces of production aids) high demands are made.

The disadvantages of using fluxes for brazing aluminum vary depending on the flux system used. In general, the application of the flux represents an additional step in the production chain, which goes hand in hand with expenditure in plant technology and for the operating personnel. To protect personnel and the environment from flux fluid, flux mist, flux dust or flux vapor, a corresponding safety and environmental effort must be operated. Corrosive fluxes, such as the chloride fluxes, must be removed immediately after the soldering process with great effort and care from the heat exchanger, since otherwise - A -

attack the material and the joints of the manufactured heat exchanger due to their corrosive effect and thus affect its technical functionality.

Special non-corrosive fluxes, such as the Nocolok flux, require for their functioning a protective gas atmosphere with a very low residual oxygen concentration, which is preferably less than 200 ppm oxygen. This is possible only in an elaborately produced, constantly monitored and readjusted atmosphere of a closed furnace system flooded with the protective gas in nitrogen. Such a brazing furnace system is referred to as CAB (Controlled Atmosphere Brazing) system.

The working temperature range of the flux must cover the working range of the solder used. If no careful coordination of solder and flux, no soldering is possible. The duration of action of flux is limited. It follows that the soldering process must be completed in a narrow time window. With the use of flux even low magnesium contents in the alloys of the components lead to a deterioration of the solderability. On the one hand, this is due to a three times higher oxidation rate of magnesium-added materials compared to magnesium-free materials. On the other hand, the forming simple and complex oxides of magnesium, such as magnesium oxide (MgO) and magnesium-aluminum oxide (MgA ^ O ₄ ), are only slightly soluble in flux. Furthermore, these magnesium oxides react with the flux and, for example, form magnesium fluorides in the product Nocolok, which additionally severely limit the effectiveness of the flux.

However, this forced abandonment of the magnesium alloy leads to significant disadvantages in terms of the properties of the aluminum alloys used in terms of strength properties and corrosion resistance.

The invention uses the advantages of current state-of-the-art techniques, flux soldering and vacuum soldering in soldering heat exchangers, without having their disadvantages, in combination with the application special materials. At the same time, the soldering process according to the invention eliminates all fluxes and the disadvantages associated with them, such as additional labor, additional production facilities or cleaning and protective measures.

Moreover, the use of magnesium-containing corrugated fin alloys is no longer a problem for the manufacture of heat exchangers, as is the case with the use of flux systems. This makes it possible to use aluminum alloys with magnesium contents greater than 0.2% and less than 2.0%, preferably less than 1.0%, in flux-free soldering of heat exchangers in CAB brazing furnaces. This leads to decisive improvements in the strength properties and the corrosion resistance of the aluminum materials used. Furthermore, by restricting special elements in the base material, as well as in the solder, the wetting properties of the base material or of the solder can be specifically improved. The most critical elements include copper (Cu), iron (Fe), magnesium (Mg), chromium (Cr), titanium (Ti), and strontium (Sr). Although a soldering connection which may be sufficient under certain circumstances can be achieved by a targeted soldering process control even without the preferred ranges listed below, this is not economically viable since both the furnace atmosphere should have oxygen contents smaller than 20 ppm and the soldering time must be extended ,

For the soldering method according to the invention, a CAB furnace system (continuous furnace or batch furnace) is preferably used, on which flux-free soldering can be carried out without a complicated vacuum furnace system.

A preferred embodiment of the method is characterized in that the gas comprises at least one noble gas of the eighth main group of the Periodic Table of the Elements, hydrogen, nitrogen, carbon dioxide, carbon monoxide, ammonia and / or fission gas products from natural gas.

A further preferred embodiment of the method is characterized in that the muffle during soldering of the components so strongly over- Increased amount of gas is supplied, that the oxygen content of the inert gas atmosphere, especially in an inlet region of the brazing furnace, is significantly less than 500 ppm (parts per million). The use of the higher amount of gas, in particular the amount of nitrogen, prevents or at least greatly reduces the penetration or entrainment of air or its components into the soldering furnace.

A further preferred exemplary embodiment of the method is characterized in that the muffle is supplied with such a greatly increased amount of gas during the soldering of the components that the oxygen content of the protective gas atmosphere, in particular in a soldering area of the soldering iron, is less than 50 ppm (parts per million), especially significantly less than 40 ppm (parts per million). Particularly preferably, the protective gas atmosphere or soldering furnace atmosphere contains less than 30 ppm (parts per million) of oxygen. By using the higher amount of gas, the amount of oxide-forming substances, such as oxygen, is significantly reduced in the inert gas atmosphere.

A further preferred exemplary embodiment of the method is characterized in that the protective gas atmosphere is heated above room temperature during soldering. An existing oxide layer is torn open during heating. By the resulting oxide-free gaps, cracks or surfaces, for example, magnesium from a core material and / or a Lotplattierung of the components reach the surface. The magnesium acts on the surface as a wetting promoter.

A further preferred embodiment of the method is characterized in that the object temperature in the soldering oven is above 300 degrees Celsius. At this object temperature, the moisture content in the soldering furnace atmosphere must be taken into account.

Another preferred embodiment of the method is characterized in that the dew point in the Lötofenatmosphäre is below minus 45 degrees Celsius. This value has proved to be particularly advantageous in the context of the present invention. A further preferred embodiment of the method is characterized in that during the heating phase in the soldering oven in a temperature range of 400 to 615 degrees Celsius, a minimum time of three minutes is not exceeded. With particular preference, times of four to eight minutes are set for the temperature range from 400 to 615 degrees Celsius. Due to the time-temperature profile according to the invention in the soldering oven, the solder wetting is improved or made possible.

A further preferred embodiment of the method is characterized in that a characteristic value SQ, which corresponds to the quotient of a division of the gas quantity, in particular of the protective gas quantity, by the cross section of the soldering furnace, is set greater than 250 meters per hour. With particular preference, values between 500 and 750 meters per hour are set for the characteristic value SQ. Setting a higher characteristic is possible, but not mandatory.

A further preferred embodiment of the method is characterized in that a characteristic value SO, which corresponds to the quotient of a division of the gas quantity, in particular of the protective gas quantity, by the heated volume of the soldering furnace, is set greater than 25 per hour. Values between 45 and 70 per hour are particularly preferably set for the characteristic value SO. Setting a higher characteristic is possible, but not mandatory.

A further preferred embodiment of the method is characterized in that a characteristic value SB, which corresponds to the quotient of a division of the gas quantity, in particular of the protective gas quantity, by the size of the component surface, is set smaller than 6 meters per hour. Particular preference is given to setting values for the characteristic value SB which are smaller than 1.5 meters per hour.

A further preferred embodiment of the method is characterized in that a characteristic value SM corresponding to the quotient of a division of

Gas volume, in particular the amount of inert gas, corresponds to the size of the heated muffle inner surface of the brazing furnace, greater than 3 meters is set per hour. For the characteristic value SM, values between 6 and 9 meters per hour are particularly preferred. Setting a higher characteristic is possible, but not mandatory.

A further preferred embodiment of the method is characterized in that a characteristic value MB, which corresponds to the quotient of a division of the size of the heated inner surface of the muffle by the size of the component surface, is set smaller than 0.7. Particularly preferred values for the characteristic MB are values which are smaller than 0.3.

A further preferred embodiment of the method relates to the brazing of heat exchangers with guide devices, in particular corrugated fins, made of an aluminum base material. Particularly preferably, tubes and / or disks of the heat exchanger also consist of exactly one or more aluminum base materials, in particular the aluminum base material of the guide devices.

A further preferred embodiment of the method is characterized in that the aluminum base material of the guide devices contains up to 1, 2 percent silicon. Particularly preferably, the aluminum base material of the guide devices contains 0.2 to 0.6 percent silicon.

A further preferred embodiment of the method is characterized in that the aluminum base material of the guide devices contains up to 0.7 percent iron. Particularly preferably, the aluminum base material of the guide devices contains up to 0.4 percent iron.

A further preferred embodiment of the method is characterized in that the aluminum base material of the guide devices contains up to 0.3 percent copper.

A further preferred embodiment of the method is characterized in that the aluminum base material of the guide means contains up to 2.0 percent, preferably up to 1, 0 percent manganese. A further preferred embodiment of the method is characterized in that the aluminum base material of the guide means contains up to 1, 0 percent magnesium. Particularly preferably, the aluminum base material of the guide devices contains up to 0.5 percent of magnesium.

A further preferred embodiment of the method is characterized in that the aluminum base material of the guide devices contains up to 0.5 percent chromium. Particularly preferably, the aluminum base material of the guide devices contains up to 0.2 percent chromium.

A further preferred embodiment of the method is characterized in that the aluminum base material of the guide means contains up to 4.5 percent, preferably up to 2.5 percent zinc.

A further preferred embodiment of the method is characterized in that the aluminum base material of the guide devices contains up to 0.2 percent titanium.

A further preferred embodiment of the method is characterized in that the aluminum base material of the guide devices contains up to 0.2 percent tin.

A further preferred embodiment of the method is characterized in that the aluminum base material of the guide means contains up to 0.2 percent zirconium.

A further preferred embodiment of the method is characterized in that the aluminum base material of the guide means contains up to 0.05 percent bismuth or bismuth.

A further preferred embodiment of the method is characterized in that the aluminum base material of the guide devices contains up to 0.05 percent strontium. A preferred embodiment of the method relates to the brazing of heat exchangers with tubes and / or disks of an aluminum base material.

A further preferred embodiment of the method is characterized in that the aluminum base material of the tubes and / or slices contains up to 1, 2 percent silicon.

A further preferred embodiment of the method is characterized in that the aluminum base material of the tubes and / or discs contains up to 0.7 percent iron. Particularly preferably, the aluminum base material of the tubes and / or discs contains up to 0.3 percent iron.

A further preferred embodiment of the method is characterized in that the aluminum base material of the tubes and / or slices contains 0.1 to 1, 2 percent copper. Particularly preferably, the aluminum base material of the pipes and / or disks contains 0.3 to 0.8 percent copper.

A further preferred embodiment of the method is characterized in that the aluminum base material of the tubes and / or discs contains up to 2.0 percent manganese.

A further preferred embodiment of the method is characterized in that the aluminum base material of the tubes and / or discs contains up to 2.0 percent, preferably up to 1, 0 percent magnesium. Particularly preferably, the aluminum base material of the tubes and / or slices contains 0.1 to 0.3 percent magnesium.

A further preferred embodiment of the method is characterized in that the aluminum base material of the tubes and / or discs contains up to 0.5 percent chromium. Particularly preferably, the aluminum base material of the tubes and / or discs contains up to 0.2 percent chromium. A further preferred embodiment of the method is characterized in that the aluminum base material of the tubes and / or discs contains up to 5.0 percent zinc.

A further preferred embodiment of the method is characterized in that the aluminum base material of the tubes and / or discs contains up to 0.3 percent titanium. Particularly preferably, the aluminum base material of the tubes and / or discs contains up to 0.1 percent titanium.

A further preferred embodiment of the method is characterized in that the aluminum base material of the tubes and / or discs contains up to 0.05 percent tin.

A further preferred embodiment of the method is characterized in that the aluminum base material of the tubes and / or discs contains up to 0.2 percent zirconium.

A further preferred embodiment of the method is characterized in that the aluminum base material of the tubes and / or slices contains up to 0.05 percent bismuth or bismuth.

A further preferred embodiment of the method is characterized in that the aluminum base material of the tubes and / or discs contains up to 0.05 percent strontium.

A further preferred embodiment of the method relates to the soldering of heat exchangers with guide devices, in particular corrugated ribs, and / or tubes and / or discs, which are provided with a Lotplattierung. Preferably, the solder plating mainly contains aluminum.

A further preferred embodiment of the method is characterized in that the Lotplattierung contains 6 to 20 percent silicon. More preferably, the solder plating contains 7 to 11 percent silicon. A further preferred embodiment of the method is characterized in that the Lotplattierung contains up to 0.8 percent iron. More preferably, the solder plating contains up to 0.2 percent iron.

A further preferred embodiment of the method is characterized in that the Lotplattierung contains up to 1, 0 percent copper. More preferably, the solder plating contains up to 0.3 percent copper.

A further preferred embodiment of the method is characterized in that the Lotplattierung contains up to 0.15 percent manganese.

A further preferred embodiment of the method is characterized in that the solder plating contains up to 2.5 percent magnesium. Particularly preferably, the solder plating contains up to 0.2 percent, preferably up to 0.1 percent magnesium.

A further preferred embodiment of the method is characterized in that the Lotplattierung contains up to 0.05 percent chromium.

A further preferred embodiment of the method is characterized in that the solder plating contains up to 4.5 percent, preferably up to 4.0 percent zinc. More preferably, the solder plating contains up to 2.0 percent zinc.

Another preferred embodiment of the method is characterized in that the solder plating contains up to 0.2 percent titanium. More preferably, the solder plating contains up to 0.1 percent titanium.

A further preferred embodiment of the method is characterized in that the solder plating contains up to 0.05 percent tin.

A further preferred embodiment of the method is characterized in that the solder plating contains up to 0.05 percent zirconium. A further preferred embodiment of the method is characterized in that the solder plating contains up to 0.3 percent bismuth or bismuth. More preferably, the solder plating contains up to 0.1 percent bismuth or bismuth.

A further preferred embodiment of the method is characterized in that the Lotplattierung contains up to 0.2 percent strontium. Particularly preferably, the solder plating contains up to 0.05 percent strontium.

Preferably, the inventive method is used for soldering heat exchangers with flow devices, in particular pipes and / or discs, and / or guide devices, in particular corrugated fins, each with or without a Lotplattierung, of one or more aluminum base materials.

Preferably, one of the aluminum base materials contains 0.7 to 2 percent, preferably 1 to 1, 5 percent manganese. This has a positive effect on the mechanical properties of the aluminum base material.

The invention is based, inter alia, on the finding that a higher iron content precludes good wettability of the core material with solder material, since it appears that wetting-manganese precipitates which inhibit wetting can be formed. Advantageously, therefore, the aluminum base material contains less than 0.40 percent, preferably less than 0.25 percent, more preferably less than 0.20 percent iron. An iron content above 0.20 percent can be compensated by an increased soldering time, whereby from about 0.25 percent iron content, if necessary, a temperature profile over the soldering time must be easily adjusted in order to achieve a good soldering result.

A further preferred embodiment of the method is characterized in that the muffle is formed from a muffle material comprising stainless steel. The muffle material preferably consists of noble steel 316L or 316LL. However, it can also be used other than muffle suitable stainless steel. Also with respect to the oven design are all typical variants, such as a pure Strahlungslötofen, a furnace with a Konvektionvorheizzone coupled to a subsequent radiation zone, or a furnace type with complete convection technology suitable.

A further preferred embodiment of the method is characterized in that during a heating phase in the soldering oven in a temperature range of minus 30 to minus 50 Kelvin before reaching the SoIi temperature of the solder a minimum time of two minutes is not exceeded. Particularly preferred times of two to five minutes are set for the temperature range of minus 30 to minus 50 Kelvin before reaching the solidus temperature of the solder. Times above six minutes are also possible, but for economic reasons not meaningful.

Further advantages, features and details of the invention will become apparent from the following description in which, with reference to the drawing, various embodiments are described in detail. It shows:

Figure 1 is a table with materials and solders, which are preferably used with the inventive method.

The invention relates to the brazing of aluminum heat exchangers in inert gas continuous brazing. An inert gas continuous soldering furnace comprises a housing having an input and an output for components. The housing entrance for the components is also referred to as the entry area of the brazing furnace. The housing outlet for the components is also referred to as the exit area of the brazing furnace. Between the inlet region and the outlet region, a muffle is formed in the interior of the brazing furnace, which is rinsed with protective gas. In the case of conventional inert gas continuous flow furnaces, an oven atmosphere with an oxygen content of approximately 500 ppm (parts per million) in the inlet area and approximately 40 ppm in the soldering area prevails during operation in the region of the oven muffle between the inlet opening and the outlet opening. With such oxygen contents in the furnace atmosphere, flux-free soldering is not possible. According to an essential aspect of the present invention, the inert gas atmosphere in the brazing furnace is improved by greatly increasing the addition of the protective gas, preferably nitrogen, so that heat exchangers can be brazed without the addition of flux.

Due to the greatly increased amount of nitrogen in the brazing oven so low-oxygen atmosphere is created that the brazing of the components can be done without flux. The use of the higher amount of nitrogen prevents the penetration or entrainment of air or its components into the brazing furnace. As a result, the content of oxide-forming substances, in particular oxygen, can be significantly reduced in the soldering oven.

In the method according to the invention can, but does not completely dispense with the use of flux. A doping of the incoming protective gas with flux or reducing substances in solid, liquid or gaseous form can be chosen freely. Due to the massive use of the protective gas, an undesirable oxidation of the aluminum surface is extremely reduced or practically prevented during the soldering process in the temperature range above room temperature. An existing oxide layer is torn open during heating. The resulting oxide-free gaps, cracks and / or areas may cause magnesium, which originates from the core material and / or a solder plating, to reach the surface. The magnesium on the surface acts as a wetting promoter. Instead of magnesium, it is also possible to use elements of the second and fifth main groups of the Periodic Table of the Elements, individually or in combination, and in different mixtures and concentrations. The method according to the invention provides inter alia the advantage that the costs for the flux can be saved. In addition, the costs of acquiring and operating a ventilation system can be eliminated. Furthermore, the costs for waste disposal are reduced. In addition, the dust and environmental pollution is reduced. The heating of the components for drying after Befluxung can be omitted. This considerably reduces the required energy expenditure.

For flux-free soldering, an oxygen level of less than 50 ppm above 300 degrees Celsius object temperature in the soldering furnace should be aimed for. Furthermore, the moisture content in the brazing furnace atmosphere is to be observed. It is a dew point less than 45 degrees Celsius in the brazing furnace atmosphere to strive for. Furthermore, the following parameters must be observed.

Inert gas quantity [Nm ³ / h] / furnace cross section [m ² ] = characteristic value code SQ [m / h]. The characteristic value SQ must be set to> 250 m / h. Normally, the value should be set between 500 m / h and 750 m / h. Setting a higher characteristic is possible, but not mandatory.

The term Nm stands for standard meter in the context of the present invention. The standard meter is a measurement of 1.0 m at a standard temperature of 20 degrees Celsius and a standard pressure of 1 bar.

Inert gas volume [Nm ³ / h] / heated furnace volume [m ³ ] = characteristic value code SO [1 / h]. The characteristic value SO must be set to> 25 1 / h. Optimally, values between 45 1 / h and 70 1 / h should be set. Setting a higher characteristic is possible, but not mandatory.

Protective gas quantity [Nm ³ / h] / component surface [m ² ] = characteristic abbreviation SB [m / h]. The characteristic value SB must be set to <6 m / h. Optimally, values <1, 5 m / h should be set.

Protective gas quantity [Nm ³ / h] / heated inner surface of the muffle [m ² ] = characteristic abbreviation SM [m / h]. The characteristic value SM must be set> 3 m / h. Optimal way values between 6 m / h and 9 m / h should be set. The setting of a higher characteristic value is possible, but not mandatory.

Muffle inner surface [m ² ] / component surface [m ² ] = characteristic abbreviation MB. The factor MB must be set to <0.7. Optimally, the factor <0.30 should be set.

In this invention, but need not completely dispense with the use of flux. Partial addition of flux on or on the component are possible and have no negative influence on areas of the component, which are soldered flux-free. A doping of the incoming protective gas with flux or reducing substances (solid / liquid / gaseous) can be chosen freely. Due to the massive use of a protective gas, further oxidation of the aluminum surface is extremely reduced or practically prevented during the soldering process in the temperature range above room temperature. The existing oxide layer is torn open during heating. Due to the resulting oxide-free gaps / cracks / surfaces, wetting of the solder to the surfaces is possible.

By means of a corresponding time-temperature profile in the soldering oven, the solder wetting is improved or made possible. During the heating-up phase in the soldering furnace in the temperature range from 400 to 615 degrees Celsius a minimum time of 3 minutes should not be undercut. Optimally, times of 4 to 8 minutes are set for the temperature range of 400 to 615 degrees Celsius. The time-temperature window in the temperature range of 400 to 615 degrees Celsius depends on alloying elements in the base material as well as protective cladding as well as in solder. The elements which influence the time interval or promote solder wetting are, for example, silicon, copper, strontium, bismuth or bismuth, magnesium.

During the heating-up phase in the soldering oven in the temperature range from minus 30 to minus 50 K, particularly preferably, a minimum time of 2 minutes should not be undershot before the solidus temperature of the solder is reached. the. Optimally, for the temperature range of solidus solder minus 30 to minus 50 K, times of two to five minutes are set. Times above 6 minutes are also possible, but not useful for economic reasons.

The advantage of a certain residence time in the temperature interval solidus solder minus 30 to minus 50 K are diffusion processes of elements of the core material in the solder plating and the homogenization of the solder as well as the base material with respect to unwanted intermetallic phases, which can be wetting inhibiting in the near-surface region.

Furthermore, in connection with certain material combinations of core and brazing materials, solidus solder minus 30 to minus 50 K of at least 2 minutes was observed while maintaining the residence time; a partial melting of the braze was observed. This means that certain parts of the solder become liquid even before the known solidus temperatures of the solder, for example 577 degrees Celsius for AISiIO. This considerably facilitates a mechanical breaking up of the oxide layers on the solder. The time-temperature window in the temperature range solidus solder minus 30 to minus 50 K is therefore dependent on alloying elements in the base material as well as protective cladding as well as in the solder. The elements influencing the time interval or influencing the solder wetting are, for example, silicon, copper, strontium, bismuth or bismuth, magnesium and iron.

For the soldering process according to the invention, it is particularly preferable to use a CAB furnace system (continuous furnace or batch furnace), on or in which flux can be soldered without a complicated vacuum furnace system. The necessary Lötofenatmosphäre should contain to achieve good quality solder joints less than or equal to 50 ppm oxygen, more preferably less than 30 ppm oxygen.

FIG. 1 shows in a table the usable materials and solders which are comparable under the boundary conditions described above

Quality of the solder joints can be achieved as in vacuum soldering or CAB soldering, compiled. The letters GW stand for basic material. The letters WR stand for corrugated rib. The letter R stands for pipe. The letter LP stands for solder plating. The letter RW stands for pipe material.

The materials and material combinations shown in the table make it possible to use alloys with a property profile improved by addition of magnesium or adapted to the respective requirements. The improvements in strength and corrosion resistance enable either stronger and longer lasting components or lighter material heat exchangers through material reduction. Flux-free production eliminates additional expenses such as inflation and drying systems as well as expenses for environmental and employee protection. The flux-free production in a CAB furnace does not require the complex technical equipment of a single or multi-chamber vacuum furnace.

Claims

Patent claims

1. A method for particular flux-free soldering of components, in particular of heat exchangers, in particular Aluminiumwerk- materials, aluminum alloys or wrought alloys, in a soldering oven, in particular a continuous soldering oven or a batch-type solder oven, which comprises a muffle, which is purged with inert gas, In order to create a protective gas atmosphere, characterized in that the muffle during soldering of the components is supplied to one or more predetermined characteristic values excessive amount of gas, in particular inert gas or reaction gas, so that a low-oxygen inert gas atmosphere is created.

2. The method according to claim 1, characterized in that the gas comprises at least one noble gas of the eighth main group of the Periodic Table of the Elements, hydrogen, nitrogen, carbon dioxide, carbon monoxide, ammonia and / or fission gas products from natural gas.

3. The method according to any one of the preceding claims, character- ized in that the muffle during soldering of the components such a greatly increased amount of gas is supplied, that the oxygen content of the inert gas atmosphere, especially in an inlet region of the brazing furnace, significantly less than 500 ppm (parts per million).

4. The method according to any one of the preceding claims, characterized in that the muffle during soldering of the components such a greatly increased amount of gas is supplied that the oxygen content of the inert gas atmosphere, in particular in a soldering area of the soldering oven, less than 50 ppm (parts per million ), in particular significantly less than 40 ppm (parts per million).

5. The method according to any one of the preceding claims, characterized in that the protective gas atmosphere is heated during the soldering above room temperature.

6. The method according to any one of the preceding claims, characterized in that the object temperature in the brazing furnace is above 300 degrees Celsius.

7. The method according to any one of the preceding claims, characterized in that the dew point in the Lötofenatmosphäre below minus 45 degrees Celsius.

8. The method according to any one of the preceding claims, characterized in that during the heating phase in the soldering oven in a temperature range of 400 to 615 degrees Celsius, a minimum time of three minutes is not exceeded.

9. The method according to any one of the preceding claims, characterized in that a characteristic value SQ, which corresponds to the quotient of a division of the gas quantity, in particular the protective gas amount, by the cross section of the brazing furnace, is set greater than 250 meters per hour.

10. The method according to any one of the preceding claims, characterized in that a characteristic value SO, which is the quotient of a division of the amount of gas, in particular the protective gas amount, by the heated volume of the soldering oven, set greater than 25 per hour.

11. The method according to any one of the preceding claims, characterized in that a characteristic value SB, which corresponds to the quotient of a division of the amount of gas, in particular the protective gas, by the size of the component surface is set smaller than 6 meters per hour.

12. The method according to any one of the preceding claims, characterized in that a characteristic value SM, which corresponds to the quotient of a division of the amount of gas, in particular the protective gas, by the size of the heated muffle inner surface of the brazing furnace, is set greater than 3 meters per hour.

13. The method according to any one of the preceding claims, character- ized in that a characteristic MB, which corresponds to the quotient of a division of the heated muffle inner surface by the size of the component surface, is set smaller than 0.7.

14. The method according to any one of the preceding claims for soldering heat exchangers with flow devices, in particular pipes and / or disks, and / or guide devices, in particular corrugated fins, of one or more aluminum base materials.

15. The method according to claim 14, characterized in that the aluminum base material of the flow and / or guide devices contains up to 0.40 percent, preferably up to 0.25 percent, particularly preferably up to 0.20 percent iron.

16. The method according to claim 14 or 15, characterized in that the aluminum base material of the flow and / or guide devices contains 0.7 to 2 percent, preferably 1 to 1, 5 percent manganese.

17. The method according to any one of the preceding claims for soldering heat exchangers with flow devices, in particular pipes and / or disks, and / or guide devices, in particular Wellrip- which are provided with a solder cladding of one or more aluminum base materials.

18. The method according to claim 17, characterized in that the aluminum base material of the solder plating contains up to 0.40 percent, preferably up to 0.25 percent, particularly preferably up to 0.20 percent iron.

19. The method according to claim 17 or 18, characterized in that the aluminum base material of the Lotplattierung 0.7 to 2 percent, preferably 1 to 1, 5 percent manganese.

20. The method according to any one of the preceding claims, characterized in that the muffle is formed from a muffle material comprising stainless steel.

21. The method according to any one of the preceding claims, characterized in that during a heating phase in the soldering oven in a temperature range of minus 30 to minus 50 Kelvin before reaching the solidus temperature of the solder, a minimum time of two minutes is not exceeded.