Patent Publication Number: US-4147537-A

Title: Composition of material for a rust-resistant steel for use at high temperatures

Description:
This application is a continuation-in-part application of Ser. No. 699,559, filed June 24, 1976, entitled NEW COMPOSITION OF MATERIAL FOR A RUST-RESISTANT STEEL FOR USE AT HIGH TEMPERATURES and now abandoned. 
    
    
     BACKGROUND AND FIELD OF THE INVENTION 
     This invention relates to an alloy having utility in fabricating automotive vehicle mufflers and more particularly mufflers which are also catalytic converters. 
     Catalytic converters are employed to reduce detrimental automobile engine emissions. Such emissions are caused, among other reasons, by insufficient burning, by soft burning, or by poor carburation, i.e., any factor that causes incomplete combustion. In effect, gasoline is not always completely burned and, therefore, the exhaust gases contain carbon monoxide, unburned hydrogen and hydrocarbons, and nitrogen oxides and nitric oxides. 
     The new composition of matter of this invention is a new rust-resistant alloy used preferably for the manufacture of catalytic converters for transforming polluting gases into nonpolluting gases. 
     The new composition comprises manganese alloyed with 
     About 1.0%-about 2.0% silicon 
     About 0.9%-about 1.9% copper 
     About 0.5%-about 0.12% carbon 
     About 0.5%-about 0.9% iron 
     About 0.2%-about 2.3% titanium 
     About 15.0%-about 22.0% chromium 
     About 2.5%-about 4.0% molybdenum 
     About 5.0%-about 10.0% aluminum 
     About 0.1%-about 0.3% selenium 
     Said manganese being present in amount less than about 70.0%. 
    
    
     The alloy may be hardened by precipitation or cold rolling; generally has a tension resistance of about 8750 to 12,980 Kgs./cm 2  and a hardness of about 180 to about 240 Brinell with an elongation of about 24% to about 53%, with an upper limit of 46% preferred. 
     Preferably the composition comprises: 
     1.6% silicon 
     1.6% copper 
     0.11% carbon 
     0.7% iron 
     0.3% titanium 
     19.0% chromium 
     3.1% molybdenum 
     8.9% aluminum 
     0.25% selenium 
     The remainder being manganese. 
     The foregoing percentages are expressed on a weight percent basis. 
     The alloy generally with an elongation of 23% to 45% is preferably used in 1.37 mm and 1.21 mm gauges. 
     3.1% OF (Mo) Molybdenum is used to increase resistance to hot chemical products with a small quantity of (Se) Selenium to improve machining. Alloys with high content of (Cr) chrome are used for strong chemical resistance to high temperatures. These will permit working with mixed chemical compounds and hot gases. 
     In accordance with this invention a new rust-resistant alloy is obtained with a long service life at the high temperatures and operating conditions found in automobile mufflers. 
     In general manner, while there has been disclosed an effective and efficient embodiment of the invention, it should be well understood that the invention is not limited to such embodiment as there might be changes made in the arrangement, disposition, and form of the parts without departing from the principal of the present invention as comprehended within the scope of the accompanying claims.