Method of brazing articles of stainless steel

Abstract

The present invention relates to a method of brazing articles of stainless steel, which method comprises the following steps: step (i) applying an iron-based brazing filler material to parts of stainless steel; step (ii) optionally assembling the parts; step (iii) heating the parts from step (i) or step (ii) to a temperature of at least about 1000° C. in a non-oxidizing atmosphere, a reducing atmosphere, vacuum or combinations thereof, and heating the parts at the temperature of at least about 1000° C. for at least about 15 minutes; step (iv) providing articles having an average hardness of less than about 600 HV1 of the obtained brazed areas. The present invention relates also to brazed articles of stainless steel.

What is claimed is: 
     
         1 . A brazed article of stainless steel comprising at least about one base material of stainless steel and an iron-based brazing filler material wherein the obtained brazed areas, pores, cracks, gaps, joints, or crevices having a tensile strength of at least about 110 N/mm 2 . 
     
     
         2 . A brazed article of stainless steel comprising at least about one base material of stainless steel and an iron-based brazing filler material wherein the obtained brazed areas, pores, cracks, gaps, joints, or crevices having an average hardness less than about 600 HV1. 
     
     
         3 . The article of stainless steel according to  claim 1 , wherein the parts or the articles obtained in step (iv), are selected from reactors, separators, columns, heat exchangers, or equipments for chemical plants or food plants, or for car industry. 
     
     
         4 . The article of stainless steel according to  claim 2 , wherein the parts or the articles obtained in step (iv), are selected from reactors, separators, columns, heat exchangers, or equipments for chemical plants or food plants, or for car industry. 
     
     
         5 . The article of stainless steel according to  claim 1 , wherein the article is being brazed heat exchanger plates, brazed reactor plates, or combinations thereof. 
     
     
         6 . The article of stainless steel according to  claim 2 , wherein the article being brazed heat exchanger plates, brazed reactor plates, or combinations thereof. 
     
     
         7 . The article of stainless steel according to  claim 5 , wherein the article having a burst pressure of at least about 60 Bar. 
     
     
         8 . The article of stainless steel according to  claim 6 , wherein the article having a burst pressure of at least about 60 Bar. 
     
     
         9 . The article of stainless steel according to  claim 7 , wherein the article having a burst pressure of at least about 80 Bar. 
     
     
         10 . The article of stainless steel according to  claim 8 , wherein the article having a burst pressure of at least about 80 Bar. 
     
     
         11 . The article according to  claim 1 , wherein the article is a heat exchanger having a heat exchanger plate area larger than about 0.20 m 2 , a burst pressure of at least about 65 Bar, and a porthole area of at least about 0.003 m 2 . 
     
     
         12 . The article according to  claim 2 , wherein the article is a heat exchanger having a heat exchanger plate area larger than about 0.20 m 2 , a burst pressure of at least about 65 Bar, and a porthole area of at least about 0.003 m 2 . 
     
     
         13 . The article of stainless steel according to  claim 1 , wherein the brazed areas, pores, cracks, gaps, joints, or crevices having a silicone content of at least about 2 wt % Si. 
     
     
         14 . The article of stainless steel according to  claim 2 , wherein the brazed areas, pores, cracks, gaps, joints, or crevices having a silicone content of at least about 2 wt % Si. 
     
     
         15 . The article of stainless steel according to  claim 1 , wherein the brazed areas, pores, cracks, gaps, joints, or crevices having a tensile strength of at least about 120 N/mm 2 . 
     
     
         16 . The article of stainless steel according to  claim 2 , wherein the brazed areas, pores, cracks, gaps, joints, or crevices having a tensile strength of at least about 120 N/mm 2 . 
     
     
         17 . The article of stainless steel according to  claim 1 , wherein the article is a heat exchanger having a plate pack of at least about three heat exchanger plates brazed together in one brazing cycle having the following steps:
 (i) applying an iron-based brazing filler material to heat exchanger plates of stainless steel;   (ii) assembling the heat exchanger plates to a plate pack;   (iii) heating the plate pack to a temperature of at least about 500° C. to equalise the temperature in the plate pack and then raising the temperature to at least about 1000° C. in a non-oxidizing atmosphere, a reducing atmosphere, vacuum or combinations thereof, and let the plate pack be brazed together at the temperature of at least about 1000° C. for at least about 15 minutes; and   (iv) providing articles having an average hardness of less than about 600 HV1 of the obtained brazed areas.   
     
     
         18 . The article of stainless steel according to  claim 2 , wherein the article is a heat exchanger having a plate pack of at least about three heat exchanger plates brazed together in one brazing cycle having the following steps:
 (i) applying an iron-based brazing filler material to heat exchanger plates of stainless steel;   (ii) assembling the heat exchanger plates to a plate pack;   (iii) heating the plate pack to a temperature of at least about 500° C. to equalise the temperature in the plate pack and then raising the temperature to at least about 1000° C. in a non-oxidizing atmosphere, a reducing atmosphere, vacuum or combinations thereof, and let the plate pack be brazed together at the temperature of at least about 1000° C. for at least about 15 minutes; and   (iv) providing articles having an average hardness of less than about 600 HV1 of the obtained brazed areas.   
     
     
         19 . The article of stainless steel according to  claim 17 , wherein the article is a heat exchanger having a plate pack up having more than nine heat exchanger plates brazed together in one brazing cycle having the following steps:
 (i) applying an iron-based brazing filler material to heat exchanger plates of stainless steel;   (ii) assembling the heat exchanger plates to a plate pack;   (iii) heating the plate pack to a temperature of at least about 1000° C. to equalise the temperature in the plate pack and then raising the temperature to at least about 1150° C. in a non-oxidizing atmosphere, a reducing atmosphere, vacuum or combinations thereof, and let the plate pack be brazed together at the temperature of at least about 1150° C. for at least about 15 minutes;   (iv) providing articles having an average hardness of less than about 600 HV1 of the obtained brazed areas.   
     
     
         20 . The article of stainless steel according to  claim 18 , wherein the article is a heat exchanger having a plate pack up having more than nine heat exchanger plates brazed together in one brazing cycle having the following steps:
 (i) applying an iron-based brazing filler material to heat exchanger plates of stainless steel;   (ii) assembling the heat exchanger plates to a plate pack;   (iii) heating the plate pack to a temperature of at least about 1000° C. to equalise the temperature in the plate pack and then raising the temperature to at least about 1150° C. in a non-oxidizing atmosphere, a reducing atmosphere, vacuum or combinations thereof, and let the plate pack be brazed together at the temperature of at least about 1150° C. for at least about 15 minutes;   (iv) providing articles having an average hardness of less than about 600 HV1 of the obtained brazed areas.