Low-temperature covering enamels for steel and aluminum

Abstract

The possibility of obtaining for steel white covering enamel with melting temperature 1000 -1100°C and firing temperature 750 -780°C and for aluminum white enamel with melting temperature 900 -950°C and firing temperature 530 -560°C is investigated. The physical and technological characteristics of the frits melted are measured and the temperature -time firing regimes with the enamel deposited in the form of slip are determined. It is established that introducing modifier oxides and glass-forming oxides makes it possible to lower the melting temperature by 15 -20% and the enamel firing temperature by 20 -30°C without introducing new components into the enamel composition.Coating enamels with melting temperature 1200 -1300°C and firing temperature interval 840 -869°C are currently used for enameling steel articles. Enamels with lower melting and firing temperatures can lower costs substantially.A literature search led to ways to lower the temperature characteristics of enamels. The following enamel compositions were chosen for investigation:alkali-earth oxides (Na 2 O : K 2 O : Li 2 O) were introduced in the ratio 3 : 2 : 1, which corresponds to a combined polyalkali effect, were introduced into enamels Nos. 1 and 4 to facilitate melting; aside from alkali-earth oxides, glass-forming oxides (SiO 2 : B 2 O 3 ) were introduced into enamels Nos. 2 and 5 in the ratio 2 : 1 to obtain a chemically more stable enamel; the ratio B 2 O 3 : P 2 O 3 in the enamels Nos. 2 and 6 is 3 : 1, which will make it possible to make the glass network even stronger and to improve the operating properties of the enamel without raising its melting temperature [1].In the present work we study the problem of obtaining white titanium enamel with melting temperature 1000 -1100°C and firing temperature 680 -700°C for steel and white enamel with melting temperature 900 -950°C and firing temperature 560 -600°C for aluminum.The enamel frits were melted in a periodic-operation Silit furnace at temperature (1000 -1100) ± 10°C. The total melting time was 3.5 -4 h. The meltings performed showed that borosilicate titanium enamels with compositions Nos. 4 and 6 were completely melted at 900 -1000°C. Gas release was moderate. The fusion process for these compositions was identical to the fusion of ordinary frit.The CLTE was investigated with a quartz dilatometer.The average values of the CLTE of enamels at temperatures 200 -500°C were (

Development and analysis of frits for enamelling AA2024, AA6082 and AA7075 aluminium alloys

“…The addition of B 2 O 3 , CaO, and BaO reduced the melting point of the frit, while B 2 O 3 and CaO additionally increased the elasticity. [ 20,27,31 ] Frits G1–G3 had the same multicomponent oxide system as frits F1–F3, but did not contain BaO and K 2 O. As expected, [ 20 ] the replacement of K 2 O with MgO (as magnesium carbonate) to obtain frit H made the enamels harder to melt and reduced their elasticity.…”

“…The first three frits developed, that is, frits A1–A3, contained a different weight percentage of the multicomponent oxide systems SiO 2 –Na 2 O–ZnO–Li 2 O–Sb 2 O 3 –Bi 2 O 3 , as suggested by the available data in the literature. [ 20,26–28 ] To soften the frits, different amounts of potassium carbonate were added to the previously obtained frits (i.e., frits A1–A3) and thus, frits B–D2 were obtained. [ 20,27 ] The addition of boric acid, barium carbonate, and calcium carbonate was introduced to frits E and F1–F3, which were composed of multicomponent oxide systems SiO 2 –Na 2 O–K 2 O–B 2 O 3 –CaO–ZnO–BaO–Sb 2 O 3 –Bi 2 O 3 .…”

“…[ 20,26–28 ] To soften the frits, different amounts of potassium carbonate were added to the previously obtained frits (i.e., frits A1–A3) and thus, frits B–D2 were obtained. [ 20,27 ] The addition of boric acid, barium carbonate, and calcium carbonate was introduced to frits E and F1–F3, which were composed of multicomponent oxide systems SiO 2 –Na 2 O–K 2 O–B 2 O 3 –CaO–ZnO–BaO–Sb 2 O 3 –Bi 2 O 3 . The addition of B 2 O 3 , CaO, and BaO reduced the melting point of the frit, while B 2 O 3 and CaO additionally increased the elasticity.…”

“…These frits also contained additions of Al 2 O 3 , which increased the hardness, strength and chemical resistance of the frits. [ 20,27,31 ] Finally, ZrO 2 , which improves heat resistance, [ 20,27,31 ] was also added to frits V1‒V3 (Al 2 O 3 –SiO 2 –Na 2 O–B 2 O 3 –ZrO 2 –CaO–K 2 O–TiO 2 –Li 2 O–V 2 O 5 ).…”

“…Excessive P 2 O 5 content decreased the chemical resistance of the enamel, while the restriction of the Al 2 O 3 content led to a low firing temperature of the enamel. Lazutkina et al [ 27 ] reported on the influence of the type and ratio of the oxides used on the melting and firing temperature of frits. A 15%–20% decrease in the melting temperature and a 20–30°C lowering of the firing temperature was observed when Na 2 O, K 2 O, and Li 2 O at a ratio of 3:2:1 were used in combination with the vitrifying oxides B 2 O 3 and P 2 O 5 at a ratio of 3:1 or SiO 2 and B 2 O 3 at a ratio of 2:1.…”