Porcelain-enameled steel sheets and frits for enameling

Frits for enameling comprising P.sub.2 O.sub.5, Sb.sub.2 O.sub.3, Al.sub.2 O.sub.3 and B.sub.2 O.sub.3 ;

• at least one oxide of Group I element of Periodic Table selected from the group consisting of Na.sub.2 O, K.sub.2 O and Li.sub.2 O;
• at least one oxide of Group II metal of Periodic Table selected from the group consisting of ZnO, BaO, CaO and SrO;
• and at least one oxide of Group IV element of Periodic Table selected from the group consisting of TiO.sub.2, SiO.sub.2 and ZrO.sub.2 ;
• containing one of the following relations of (1), (2) or (3):
• (1) 45 wt %.ltoreq.P.sub.2 O.sub.5 .ltoreq.65 wt %, 5 wt %.ltoreq.Sb.sub.2 O.sub.3 .ltoreq.15 wt %, 2 wt %.ltoreq.Al.sub.2 O.sub.3 .ltoreq.10 wt %, 0.5 wt %.ltoreq.B.sub.2 O.sub.3 .ltoreq.5 wt %, 7 wt %.ltoreq.Na.sub.2 O+K.sub.2 O+Li.sub.2 O<15 wt %, 7 wt %.ltoreq.ZnO+BaO+CaO+SrO.ltoreq.20 wt %, 1 wt %.ltoreq.TiO.sub.2 +SiO.sub.2 +ZrO.sub.2 .ltoreq.10 wt %,
• (2) 50 wt %.ltoreq.P.sub.2 O.sub.5 .ltoreq.65 wt %, 7 wt %.ltoreq.Sb.sub.2 O.sub.3 .ltoreq.12 wt %, 3 wt %.ltoreq.Al.sub.2 O.sub.3 .ltoreq.8 wt %, 0.5 wt %.ltoreq.B.sub.2 O.sub.3 .ltoreq.4 wt %, 11.5 wt %.ltoreq.Na.sub.2 O+K.sub.2 O+Li.sub.2 O.ltoreq.13 wt %, 11 wt %.ltoreq.ZnO+BaO+CaO.ltoreq.14 wt %, 1 wt %.ltoreq.TiO.sub.2 +SiO.sub.2 +ZrO.sub.2 .ltoreq.8 wt %,
• (3) 50 wt %.ltoreq.P.sub.2 O.sub.5 .ltoreq.65 wt %, 0 wt %<Sb.sub.2 O.sub.3 <5 wt %, 3 wt %.ltoreq.Al.sub.2 O.sub.3 .ltoreq.8 wt %, 0.5 wt %.ltoreq.B.sub.2 O.sub.3 .ltoreq.4.6 wt %, 9 wt %.ltoreq.Na.sub.2 O.sub.3 +K.sub.2 O+Li.sub.2 O<15 wt %, 9 wt %.ltoreq.ZnO+BaO+CaO.ltoreq.18 wt %, 3 wt %.ltoreq.TiO.sub.2 +SiO.sub.2 +ZrO.sub.2 .ltoreq.4.5 wt %.

A porcelain enameled steel sheet which comprises an aluminum-zinc alloy-plated steel sheet and a porcelain enamel coating layer as an upper most layer of the steel sheet, wherein an interstitial layer between the plating layer and the enamel coating layer comprises at least one member selected from the group consisting of:

• (1) a coating layer comprising at least one member selected from the group consisting of Ni, Co, Mo, Mn, Al, Al--Zn, Al--Ni, Al--Ni--Zn, Ni--P, Ni--Co--P and Co--P;
• (2) a chromate layer;
• and
• (3) a coating layer comprising at least one member selected from the group consisting of zinc phosphate, manganese phosphate and aluminum phosphate.

Frits for enameling comprising P.sub.2 O.sub.5, Al.sub.2 O.sub.3 and B.sub.2 O.sub.3 ;

• at least one oxide of Group I element of Periodic Table selected from the group consisting of Na.sub.2 O, K.sub.2 O and Li.sub.2 O;
• at least one oxide of Group II metal of Periodic Table selected from the group consisting of ZnO, BaO and CaO;
• and at least one oxide of Group IV element of Periodic Table selected from the group consisting of TiO.sub.2, SiO.sub.2 and ZrO.sub.2 ;
• containing the following relations of:
• 50 wt %.ltoreq.P.sub.2 O.sub.5 .ltoreq.65 wt %, 3 wt %.ltoreq.Al.sub.2 O.sub.3 .ltoreq.8 wt %, 0.5 wt %.ltoreq.B.sub.2 O.sub.3 .ltoreq.4.6 wt %, 9 wt %.ltoreq.Na.sub.2 O+K.sub.2 O+Li.sub.2 O<15 wt %, 9 wt %.ltoreq.ZnO+BaO+CaO.ltoreq.18 wt %, 3 wt %.ltoreq.TiO.sub.2 +SiO.sub.2 +ZrO.sub.2 .ltoreq.4.5 wt %.