High strength and sagging resistant fin material

摘要

The present invention provides a method for producing AlMn strip or sheet for making components by brazing, as well as the products obtained by said method. In particular this method is related to fin materials used in heat exchangers. The fins can be delivered with or without a cladding depending on application.;Rolling slabs are produced from a melt which contains 0.3-1.5% Si, ≦0.5% Fe, ≦0.3% Cu, 1.0-2.0% Mn, ≦0.5% Mg, ≦4.0% Zn, ≦0.3% each of elements from group IVb, Vb, or VIb elements, and unavoidable impurity elements, as well as aluminum as the remainder in which the rolling slabs prior to hot rolling are preheated at a preheating temperature of less than 550° C., preferably between 400 and 520° C., more preferably between 450 and 520° C. to control the number and size of dispersoid particles, and the preheated rolling slab is hot rolled into a hot strip. The strip is thereafter cold rolled into a strip with a total reduction of at least 90%, and the cold rolled strip is heat treated to obtain a 0.2% proof stress value that is 50-90% of its proof stress value in the as cold rolled condition to a proof stress value in the range between 100 and 200 MPa. The strip may alternatively be produced by twin-roll strip casting.;The composition of the melt tailors the microstructure development during the complete processing to give the desired post braze properties and performance during brazing in combination with adequate delivery properties of the strip. In particular the high post braze strength combined with a good sagging resistance and low susceptibility to liquid core penetration during brazing, as well as a relatively good formability in the delivery condition prior to fin forming.

主权项

1. A sagging resistant strip produced by
a) casting a melt comprising:
0.3-1.5 wt % Si,≦0.5 wt % Fe,≦0.3 wt % Cu,1.0-2.0 wt % Mn,≦0.5 wt % Mg,≦4.0 wt % Zn,≦0.3 wt % each of dispersoid forming elements from group IVb, Vb, or VIb, andunavoidable impurity elements, each at most 0.05 wt %, in a total amount of at most 0.15 wt %, the rest aluminium, to obtain an ingot; b) preheating the resulting ingot at a temperature of less than 550° C. to form dispersoid particles; c) hot rolling to obtain a strip, d) cold rolling the strip obtained in step c) with a total reduction of at least 90%, resulting in a strip having a first proof stress value; e) followed by a heat treatment to the delivery temper to soften the material by a tempering without any recrystallisation of the strip alloy, in such a way that a strip is obtained having a second proof stress value which is 10-50% lower than the first proof stress value (obtained directly after cold rolling in step d), and lying in the 0.2% proof stress range of 100-200 MPa; wherein the sagging resistant strip has a 0.2% proof stress value after brazing of at least 60 MPa and a sagging resistance of ≦35 mm when measured on a 0.10 mm thick strip using a cantilever beam length of 60 mm.