SE529913C2 - Brazing articles of stainless steel, e.g. large heat exchanger involves applying an iron-based brazing filler material to parts of stainless steel, heating the parts, and providing brazed areas with specific average hardness - Google Patents

Abstract

Brazing articles of stainless steel involves applying an iron-based brazing filler material to parts of stainless steel; optionally assembling the parts; heating the parts to at least 1000[deg]C in a non-oxidizing atmosphere, a reducing atmosphere and/or vacuum, and heating the parts to at least 1000[deg]C for at least 15 minutes; providing articles having an average hardness of less than 600 HV1 of the obtained brazed areas; and optionally repeating one or more of applying step, assembling step and heating step. An independent claim is also included for a brazed article of stainless steel comprising at least one base material of stainless steel and an iron-based brazing filler material. The obtained brazed areas, pores, cracks, gaps, joints, or crevices have a tensile strength of at least 110 N/mm 2> and an average hardness of less than 600 HV1.

Description

529,913 on the obtained soldered areas; and step (v) optionally, repeating one or more of step (i), step (ii) and step (iii).

According to an alternative aspect of the present invention there is provided a method of soldering stainless steel heat exchangers having a heat exchanger plate surface greater than 0.20 m 2 and a gate holding area of at least 0.003 m 2, which comprises (i) applying iron-based solder to stainless steel heat exchanger plates steel, (ii) joining the heat exchanger plates, (iii) heating the joined heat exchanger plates from step (ii) to a temperature of at least 1000 ° C in an atmosphere which is non-oxidizing, reducing, vacuum or combinations thereof for at least 15 minutes, (iv) providing stainless steel heat exchangers having an average hardness of less than 600 HV1 on the obtained soldered joints.

The present invention further relates to a stainless steel article (article) obtained by the method, wherein the obtained soldered surfaces, joints, pores, cracks, gaps or gaps have an average hardness of less than 600 HV1. Other alternative embodiments of the invention are defined by the independent claims and in the dependent claims.

Although the thermal expansion coefficient is the same for a small object and a large object of the same material, the larger object will have a larger total expansion. If one of two objects, with the same length at the same temperature is heated, the difference in length will be proportional to the size of the object for the same temperature difference. Both of these factors give rise to large gaps, which the solder material must succeed in filling. Thus, size, i.e. the surface area, length, width, thickness, etc. of a metal object has an effect on the accuracy of soldered joints or soldered areas, since the thermal expansion of the parts will differ and may give rise to uneven fit and large gaps. . Other cases of uneven fit may be caused by the design of the parts to be joined, movements during soldering of the objects, or by the manufacture of parts to be joined.

Therefore, the ability to fill and seal is an important aspect when joints or areas etc. are to be soldered.

Copper (Cu) has a good ability to seal large gaps. One reason for not using Cu-soldered objects is the limiting properties of the Cu-solder, e.g. Cu can cause various types of corrosion problems. The most obvious problem is that copper is consumed due to corrosion. The consumption of copper can reduce the mechanical strength of the object and the object can start to leak. The release of Cu corrosion products and Cu ions to the environment of an object can cause galvanic corrosion on other parts of the same system where the object is installed. Silver solder may be an option, but is not normally used because the price of silver is high.

Nickel (Ni) solder contains chromium (Cr), which has better corrosion resistance than Cu solder, but Ni solder has some disadvantages. One of these is that nickel can be released from the nickel solder when used in e.g. water applications. The amount of nickel in e.g. tap water is limited by legislation. Ni ions can also cause galvanic corrosion in other parts of the same system where the object is installed.

An important factor for the strength is how large gaps or gaps the solder must succeed in filling.

The capacity of the nickel solder to fill gaps is limited and nickel solder material can also lose strength in large gaps, i.e. gaps which are larger than 0.076 mm, see e.g. ASM manual vol. 6, Welding, Brazing, and Soldering, first printing 1993 / Brazing of stainless steel, pages 911-913. Thus, large nickel soldered objects are therefore very difficult to produce.

The choice of special solder for specific applications depends on various factors.

Basic considerations are temperature and materials to be soldered. In any soldering process, the solder material must have a solidification temperature high enough to provide the required properties to solder the assembly. The process needs a melting temperature which is low enough to be compatible with the temperature capacity of the parts to be joined.

In accordance with one aspect of the present invention, there is provided a method of making stainless steel articles (articles) by soldering a stainless steel base material which provides a homogenized joint of the alloy between the base material or bases. The solder alloy comprises iron as the main component and the alloy may be an iron-based alloy or an iron-based solder material. The iron-based solder material can be produced by gas atomization or water atomization, by melt spinning, mechanical alloying or by crushing ingots.

When a joint is soldered, it is suitable that the solder material wets the parts of the object, which are to be soldered together, and that the solder material can flow into gaps, joints, pores, etc. during the soldering. The melting point of the solder is suitably below the melting point of the base material in the parts. A relevant property of the solder is the ability to fill gaps, joints, pores, etc. Nickel-based materials have a poorer ability to fill gaps, thus large objects such as large nickel-soldered heat exchangers are very difficult to produce.

The solder can be made as a sheet, a powder mixed with a binder to form a paste, or the solder can be dispersed in a mixture of binder and liquid, which can be painted or sprayed on a surface of base material.

The method according to the invention comprises the following steps: step (i) application of iron-based solder material to stainless steel parts; step (ii) optionally, joining the parts; step (iii) heating the parts from step (i) or step (ii) to a temperature of at least 1000 ° C in a non-oxidizing atmosphere, a reducing atmosphere, vacuum or combinations thereof; step (iv) providing articles having an average hardness of less than 600 HV1 on the obtained brazed areas; and step (v) optionally, repeating one or more of step (i), step (ii) and step (iii).

According to an alternative aspect of the invention, the method comprises the following steps: step (i) applying iron-based solder to stainless steel parts; step (ii) optionally, joining the parts; step (iii) heating the parts from step (i) or step (ii) to a temperature of at least 1000 ° C in a non-oxidizing atmosphere, a reducing atmosphere, vacuum or combinations thereof; step (iv) sealing or filling of joints. pores, gaps, cracks or gaps larger than 76 μm; and step (v) optionally, repeating one or more of step (i), step (ii) and step (iii).

The iron-based solder can be applied as a powder or as a paste, one way of applying iron-based solder can be in the form of strands or drops by pressing it through a nozzle. Another way is to apply uniform solder material may be to apply a binder in the form of drops or strands to the base material and then spread the solder powder over the surface.

Soldering flat surfaces and forming tight joints can be difficult to achieve with conventional methods. Therefore, the iron-based solder material can be applied to flat surfaces or large surfaces with the help of solder traps (capillary force switches). The solder traps can be in the form of grooves, grooves, passages, passages, v and u shaped paths or passages etc. or in the form of nets etc. The iron-based solder material can be applied in the solder traps or in the vicinity of them. During the heating of the parts which have iron-based solder material, the solder material will till surface to the surfaces where the capillary force can be broken and solder the parts together when the temperature of the objects reaches the solidus temperature (solidification temperature) of the iron-based solder material.

Thus, the soldered areas provide closed or sealed gaps, joints, etc. between flat surfaces where it is otherwise difficult to solder uniformly. The solder traps enable soldering of surfaces having large gaps, parts having an odd shape, etc. The method according to another alternative aspect may also comprise repeating step (i), and applying the iron-based solder material to one or more additional parts, or on articles provided in step (iv); and joining in step (ii) the parts or objects of the repeated step (i) with one or fl your parts or with objects provided in step (iv), and repeating steps (iii) and step (iv). This aspect enables the production of objects having a complex design, which must be soldered in a stepwise manner.

The process according to a further alternative aspect may also comprise that the soldering in step (iii) takes place in the presence of inert gas or active shielding gas. According to an alternative aspect, the heating or soldering may be carried out in the presence of one or more of the gases selected from the group consisting of helium, argon, nitrogen, hydrogen, carbon dioxide, or one or more of the mentioned gases in combination with vacuum.

The process according to an alternative aspect of the process may also comprise heating in step (iii) to a temperature of at least 1100 ° C. According to another alternative aspect of the process, step (iii) comprises heating to a temperature of at least 1150 ° C. The heating can be performed in less than 15 minutes according to an alternative aspect, but longer soldering times are also relevant for many applications. The parts or objects can be heated to temperatures at which the solder material melts.

According to a further alternative aspect of the present method, soldering zones or soldering areas, such as for example soldered joints, pores, cracks, gaps, gaps, etc. can be provided which have an average hardness of less than 600 HV1.

According to a further alternative aspect of the present method, soldering zones or soldering areas may be provided which have an average hardness of less than 500 HV1. According to a further alternative aspect of the present method, soldering zones or soldering areas may be provided which have an average hardness of less than 400 HV1. According to a further alternative aspect of the present method, soldering zones or soldering areas may be provided which have an average hardness of less than 350 HV1. According to a further alternative aspect of the present method, soldering zones or soldering areas may be provided which have an average hardness of less than 300 HV1.

. Since the iron-based solder has flow properties and wetting properties to penetrate into gaps, the iron-based solder will create bonds to the base material, close gaps, and be able to join flat surfaces by soldering. According to an alternative aspect of the invention, the iron-based solder may seal or fill pores, cracks, gaps, joints or gaps larger than 1000 μm, and may seal or fill pores, cracks, gaps, joints or gaps larger than 3000 μm or more. According to another alternative aspect of the process, pores, cracks, gaps, joints or gaps larger than 250 μm may be sealed or filled by the iron-based solder material and provide soldering zones or soldering areas having an average hardness of less than 350 HV1. According to another alternative aspect of the process, pores, cracks, gaps, joints or gaps larger than 1000 μm may be sealed or filled by the iron-based solder material and provide soldering zones or soldering areas having an average hardness of less than 350 HV1.

According to another alternative aspect of the process, step (iv) may comprise sealing or filling pores, cracks, gaps, joints or gaps larger than 300 μm or combinations thereof, and providing soldering areas having an average hardness of less than 350 HV1 measured at a center line or near a center line of the soldered area of the filled gap which is greater than 250 μm.

In a further alternative aspect, step (iv) may comprise sealing or filling pores, cracks, gaps, joints or gaps larger than 350 μm or combinations thereof, and providing soldering areas having an average hardness of less than 350 HV1 measured at a center line or near a center line of the s soldered area of the filled gap greater than 300 μm. According to another alternative aspect, step (iv) may comprise sealing or filling pores, cracks, gaps, joints or gaps larger than 500 μm or combinations thereof, and providing soldering areas having an average hardness of less than 390 HV1 measured at a center line or near a center line of the soldered area of the filled gap greater than 400 μm.

The desired amount of solder material supplied to the contact points which are soldered together in any of the described ways or in a manner. any other way. The solder material can cover an area that is slightly larger than the contact joint point.

The contact joints can have a diameter of at least 0.5 mm.

According to the present process, any suitable iron-based solder can be used.

Suitable iron-based solder materials may be selected from the materials described in WO 02/38327, WO 02/098600, US 3,736,128, US 4,402,742, US 4,410,604, US 4,516,716, US 6,656,292, or EP 0 418 606. According to an alternative aspect of the present method, the iron-based solder material is selected from the materials described in WO 02/38327 or in WO 02/098600. According to another alternative aspect of the present method, the iron-based solder material may comprise one or more of Si, B, P, Mn, C, or Hf. According to another alternative aspect of the present process, the iron-based solder material may comprise 9-30% by weight Cr, 5-25% by weight Ni, and at least one of 0-25% by weight Si, 0-6% by weight B, 0-15% by weight P, 0-8 wt%, Mn, 0-2 wt% C, 0-15 wt% Hf, and as an alternative balanced with other elements. According to another alternative aspect of the present process, the iron-based solder material may comprise at least 40% by weight Fe, 14-21% by weight Cr, 5-21% by weight Ni, 6-15% by weight Si, 0.2-1.5% by weight B, and as a options balanced with other elements. According to another alternative aspect of the present process, the iron-based solder material may comprise at least 40% by weight Fe, 14-21% by weight Cr, 5-21% by weight Ni, 4-9% by weight Si, 4-9% by weight P, and as a options balanced with other elements. According to another alternative aspect of the present method, the iron-based solder material may comprise at least 40% by weight Fe, 14-21% by weight Cr, 5-21% by weight Ni, 7-15% by weight P, and as an alternative balanced with other elements. The present invention also relates to a stainless steel article obtained by the present process. The present invention further relates to a soldered article of stainless steel which comprises at least one base material of stainless steel and a solder material where the obtained soldered surfaces, pores, cracks, gaps or gaps have a tensile strength of at least 110 N / mm 2. According to another alternative aspect, the resulting soldered areas, pores, cracks, gaps or gaps may have a tensile strength of at least 120 N / mm 2.

The present invention also relates to a stainless steel article comprising at least one stainless steel base material and a stainless solder material where the resulting brazed areas, pores, cracks, gaps or gaps have an average hardness of at least 600 HV1. In an alternative aspect, the brazed article may comprise at least one stainless steel base material and a stainless solder material where the resulting soldered surfaces, pores, cracks, gaps or gaps have an average hardness of at least 500 HV1. According to another alternative aspect, the soldered article may comprise at least one stainless steel base material and a stainless solder material where the obtained soldered surfaces, pores, cracks, gaps or gaps have an average hardness of at least 450 HV1. According to another further alternative aspect, the soldered article may comprise at least one stainless steel base material and a stainless steel solder material where the resulting soldered surfaces, pores, cracks, gaps or gaps have an average hardness of at least 350 HV1. The "at least one stainless steel base material" according to an alternative of the invention may be a stainless steel base material soldered together with the iron-based solder material. The “at least one base material of stainless steel” according to another alternative of the invention, the iron-based solder material can solder a base material of stainless steel with another base material of another metal alloy.

According to an alternative aspect, the objects or parts may be selected from reactors, separators, columns, heat exchangers, or equipment for chemical or food plants, or for the automotive industry. According to another alternative aspect, the objects may be heat exchangers, plate reactors, or combinations thereof. According to an alternative aspect, the objects may be soldered heat exchanger plates, soldered reactor plates or combinations thereof, which have an burst pressure of at least. 60 Bar. According to soldered heat exchanger plates, soldered reactor plates or combinations thereof, which have another alternative aspect, the objects can be burst pressures of at least 65 Bar. According to another alternative aspect, the objects may be soldered heat exchanger plates, soldered reactor plates or combinations thereof, which have a burst pressure of at least 80 Bar. According to a further. alternatively, the objects may be brazed heat exchanger plates having a heat exchanger plate surface greater than 0.20 m2, an burst pressure of atmirISIOrIG 65 Bar, and a gate hole area greater than 0.003 m2.

According to a further alternative aspect of the invention, the articles can be provided where the soldered areas, pores, cracks, joints or gaps have a silicon content of at least 2% by weight of Si. In the following, the present invention will be explained in more detail with the aid of the accompanying photographs.

Brief description of the figures Figure 1 is a photograph showing a cross section of a part of a heat exchanger.

Figure 2 is a schematic drawing of a cross section of a joint.

Figure 3 is a photograph showing a cross section of a joint on which hardness tests have been performed.

Detailed description of the figures Figure 1 shows that the iron-based solder material has succeeded in filling large gaps, and that it is possible to solder with large quantities of solder material. The soldered joints of the large heat exchangers are therefore characterized in that there are amounts of applied solder material and also large homogenized zones. A portion of the solder and a portion of the thickness of the original plate have been mixed in the homogenized ZOHBH.

Figure 2 schematically shows the relationship between different parameters in a soldered gap or joint, which is soldered with the solder material F. The letter A represents the plate thickness of the plate E which also represents base material E. B represents the minimum thickness of the soldered gap or joint between the base material E or the plates E, C represent the greatest thickness of a soldered gap or joint without any pores, cracks or passages, and the letter D represents the greatest thickness of a soldered gap or joint, where pores, cracks or passages G open but are still closed. If there are no traces of pores, cracks or passages then C = D. For nickel-based solder materials, C = D is less than C = D for iron-based solder materials. The presence of pores, cracks or passages makes the soldered zone less strong.

Figure 3 is a photograph showing a cross section of a joint on which hardness tests have been performed. The average hardness is calculated as a numerical mean and depends on the number of tests.

The invention will be further illustrated in the Examples for the purpose of clarifying the invention and not limiting its scope of protection. Unless otherwise indicated, percent is given as weight percent (wt%) in the examples and tables.

Example 1 Experimental samples having a geometry similar to the plate pattern inside soldered thin-walled pressed heat exchanger plates were used for the experiment. The amount of solder applied was about 16 to 20 g per 4 solder points. A nickel-based solder Bni-5 according to AWS A5.8 AMS specification for solder was compared with iron-based solder comprising 56 wt% Fe, 17 wt% Cr, 12 wt% Ni, 12 wt% Si, and 1 wt% B.

The solder was applied to samples having gaps of 0.3-0.4 mm and the samples were heated in an oven in a non-oxidizing atmosphere to a temperature of approx. 1200 ° C. The test results are summarized in Table 1. 10 15 20 529 913 12 Table 1 Sample Ni-based Iron BNi-52 baserazt [g] [N / mm] [N / mm] 16 109 123 1 8 1 10 1 26 20 106 1 51 The experimental results show that the Fe-based solder can both fill large gaps see Figure 1, and can at the same time provide very good strength compared with Ni-based solder. Even with the sample quantities, it is shown that the Fe solder has the best mechanical strength of the tested weights. Figure 1 shows a cross section of a heat exchanger soldered with Fe-based solder. The visas clock shows that 0.4-0.6 mm gaps have been sealed.

Example 2 It has now been found that iron-based solder not only has the ability to fill large gaps but also that large gaps have a high mechanical strength, which makes it suitable for soldering, for example, large heat exchangers or flat surfaces for, for example, reactor plates. Experiments were performed by comparing the amount of solder with tensile strength, the results are summarized in Table 2.

Table 2 Sample Iron-based solder (recovery) [g] [N / mm] 25 162 55 227 Example 3 A series of experiments were performed where the heat treatment cycle of the soldering process was changed to obtain as good a filling as possible. A significant difference was detected, even with very short heat treatment cycles (5 min), very good filling was obtained for iron-based solder. The solder tests for the ability to fill gaps were performed at 1100 ° C where nickel-based solder (Bni-5) solder was compared to an iron-based solder comprising 56 wt% Fe, 17 wt% Cr, 12 wt% Ni, 12 wt% Si, and 1% by weight B. The test results are summarized in Table 3. 5 in Table 3 Time C Figure 2 C Figure 2 [minutes] BNi-5 iron-based solder [μm] [Hm] 5 1 30 800-1200 15 1 80 800-1200 30 220 800-1200 150 300 800-1200 Example 4 Hardness tests were performed on a joint with equal sealing gaps between two plates of base material (type 316). The experiments were carried out at equal distances from the base material in the center of the joint. The hardness measurements HV1 were performed according to ASTM E92-82 (Standard test method for Vickers Hardness of Metallic Materials) and EN ISO 6507-1 (Metallic materials - Vickers hardness test- Part 1: Test method (ISO 6507-1: 1997) and a comparison was made between a joint of Bni-5 and a joint of Fe-based material comprising 56 wt% Fe, 17 wt% Cr, 12 wt% Ni, 12 wt% Si, 15 and 1 wt% B. The test results are summarized in Table 4.

Table 4 Joint of BNi-5 Joint of iron-based [HV1] material [HV1] 490 _ 260 600 210 520 280 480 270 The hardness test results show that the BNi-5 joint is harder than the joint of iron-based material. Thus the BNi-5 joint shows less extensibility and therefore lower strength than the joint according to the invention of iron-based solder, which is illustrated by lower hardness values for the joint of iron-based iodine. Therefore, the BNi-5 joint is brittle compared to the iron-based solder joint.

Example 5 Hardness tests were performed on large joints closed with Fe-based iodine comprising 56 wt% Fe, 17 wt% Cr, 12 wt% Ni, 12 wt% Si, and 1 wt% B.

The experiments were performed where the soldered joint has filled a gap larger than 1000 μm and the positions where the test was performed are as in Figure 3, but the photo in Figure 3 is not a photo of the joint in this example. The result was 349 HV1, 336 HV1, 210 HV1, 197 HV1, 250 HV1, 300 HV1, and 287 HV1, giving an average hardness of 275 HV1.

Claims (31)

10 15 20 25 30 (iV) 1. (V) A method of soldering stainless steel articles, comprising: applying ferrous solder to stainless steel parts; optional, joining the parts; heating the parts of step (i) or step (ii) to a temperature of at least 1000 ° C in an atmosphere which is non-oxidizing, reducing, vacuum or combinations thereof, for at least 15 minutes; sealing or filling of joints, pores, gaps, cracks or gaps larger than 76 μm and providing objects having an average hardness of less than 600 HV1 on the obtained brazed areas; and optionally, repeating one or more of step (i), step (ii) and step (m). The method of claim 1, wherein step (v) comprises repeating step (i), and applying iron-based solder to one or more additional parts, or to objects; and joining in step (ii) the parts or objects of the repeated step (i) with one or more parts or with objects, and repeating step (iii) and step (iv). A method of soldering stainless steel heat exchangers having a heat exchanger plate surface greater than 0,20 m2 and a gate holding area of at least 0,003 m2, comprising: (i) (ii) (iii) (iV) application of iron-based solder stainless steel ; joining the heat exchanger plates; on heat exchanger plates by heating the joined heat exchanger plates from step (ii) to a temperature of at least 1000 ° C in an atmosphere which is non-oxidizing, reducing, vacuum or combinations thereof for at least 15 minutes; providing stainless steel average hardness of less than 600 HV1 on the resulting soldered joints. heat exchangers having a 10 15 20 25 30 529 913 16 A method according to any one of the preceding claims, wherein the iron-based solder material in step (i) is obtained by means of gas atomization, water atomization, crushing of ingots, mechanical alloy or by means of melt spinning. A method according to any one of the preceding claims, wherein step (i) also comprises applying the iron-based solder material as a powder or a paste or combinations thereof. A method according to claim 5, wherein step (i) also comprises applying the iron-based solder material in strands, or drops, or applying the iron-based solder material by means of solder traps. A method according to claim 6, wherein plumb traps are in the form of grooves, passages, scratches, passages, v- or u-shaped paths, paths, nets, or combinations thereof, on parts or objects. A process according to any one of the preceding claims, wherein the atmosphere in step (iii) is an inert gas, a shielding gas, or combinations thereof. A process according to any one of the preceding claims, wherein the atmosphere in step (iii) is one or more of the gases selected from the group consisting of helium, argon, nitrogen, hydrogen, carbon dioxide. A process according to any one of the preceding claims, wherein step (iii) comprises heating to a temperature of at least 1100 ° C. A process according to any one of the preceding claims, wherein step (iii) comprises heating to a temperature of at least 1150 ° C. A method according to any one of the preceding claims, wherein step (iv) comprises sealing or filling pores, cracks, joints, gaps or gaps larger than 250 μm. or combinations thereof, and providing soldered areas having an average hardness of less than 350 HV1 measured at one or near a center line of the soldered area. A method according to any one of claims 1 to 11, wherein step (iv) comprises sealing or filling pores, cracks, joints, gaps or gaps larger than 300 μm, or combinations thereof, and providing soldered areas having an average hardness less than 350 HV1 measured at one or near a center line of the soldered area of a filled gap greater than 250pm. A method according to any one of claims 1 to 11, wherein step (iv) comprises closing or filling pores, cracks, joints, gaps or gaps larger than 350 μm, or combinations thereof, and providing soldered areas having an average hardness less than 350 HV1 measured at one or near a center line of the soldered area of a filled gap greater than 300pm. A method according to any one of claims 1 to 11, wherein step (iv) comprises closing or filling pores, cracks, joints, gaps or gaps larger than 500 μm, or combinations thereof, and providing soldered areas having an average hardness less than 390 HV1 measured at or near a center line of the brazed area of a filled gap greater than 400pm. A method according to any one of the preceding claims, wherein the iron-based solder comprises one or fl era of Si, B, P, Mn, C, or Hf. The method of claim 16, wherein the iron-based solder material comprises 9-30 wt% Cr, 5-25 wt% Ni, and at least one of 0-25 wt% Si, 0-6 wt% B, 0-15 wt% P , 0-8 wt% Mn, 0-2 wt% C and 0-15 wt% Hf. The method of claim 17, wherein the iron-based solder material comprises at least 40% by weight Fe, 14-21% by weight Cr, 5-21% by weight Ni, 6-15% by weight Si, 0.2-1.5% by weight B. 10 15 20 25 30 529 913 18 The method of claim 17, wherein the iron-based solder comprises at least 40% by weight Fe, 14-21% by weight Cr, 5-21% by weight Ni, 4-9% by weight Si, 4-9% by weight P. The method of claim 17, wherein the iron-based solder material comprises at least 40% by weight Fe, 14-21% by weight Cr, 5-21% by weight Ni, 7-15% by weight P. A stainless steel article obtained by the method of any one of claims 1, 2, and 4 to 20. A soldered stainless steel article according to claim 21, comprising at least one stainless steel base material and an iron-based solder material having the obtained soldered surfaces, pores, cracks, gaps, joints or tensile strength of at least 110 N / mm? the columns have one A stainless steel solder article according to claim 21 or 22, comprising at least one stainless steel base material and an iron-based solder material wherein the resulting soldered surfaces, pores, cracks, gaps, joints or gaps have an average hardness of at least 600 HV1. Stainless steel articles according to claims 21, 22 or 23, wherein the parts or articles obtained in step (iv) are selected from reactors, separators, columns, heat exchangers, or equipment for chemical or food or automotive plants. A stainless steel article according to any one of claims 21 to 24, wherein the article is soldered heat exchangers, soldered heat exchangers and soldered reactors. reactors or combinations of soldered An article of stainless steel obtained by the method according to any one of claims 1 to 20, the object being soldered heat exchangers. 10 15 529 913 19 An article according to claim 25 or claim 26, wherein the article has an burst pressure of at least 60 Bar. An article according to claim 27, wherein the article has an burst pressure of at least 80 Bar. An article according to any one of claims 25 to 28, wherein the article is a heat exchanger having a heat exchanger plate surface greater than 0.20 m2, an burst pressure of at least 65 Bar, and a gate holding area of at least 0.003 m2. A stainless steel article according to any one of claims 21 to 29, wherein the brazed areas, pores, cracks, gap joints or gaps have a silicon content of at least 2% by weight of Si. A stainless steel article according to any one of claims 21 to 30, wherein the brazed areas, pores, cracks, gap joints or gaps have a tensile strength of at least 120 N / mm?