Steel sheet with hot dip galvanized zinc alloy coating and process to produce it
Steel strip provided with a hot dip galvanized zinc alloy coating layer, in which the coating of the steel strip is carried out in a bath of molten zinc alloy, the zinc alloy in the coating of: 0.3-2.3 weight % magnesium; 0.6-2.3 weight % aluminum; optional <0.2 weight % of one or more additional elements; unavoidable impurities; the remainder being zinc in which the zinc alloy coating layer has a thickness of 3-12 μm.
1. Steel strip provided with a hot dip galvanized zinc alloy coating layer, wherein the zinc alloy consists of:
1.6-1.9 weight % aluminium,
wherein magnesium is present such that the amount of aluminium in weight % is the same as the amount of magnesium in weight % plus or minus a maximum of 0.3 weight %;
optional <0.2 weight % of one or more additional elements selected from the group consisting of Pb, Sb, Ti, Ca, Mn, Sn, La, Ce, Cr, Ni, Zr and Bi;
unavoidable impurities;
the remainder being zinc;
wherein the zinc alloy coating layer has a thickness of 3-12 μm,
wherein the silicon content in the zinc alloy layer is below 0.0010 weight %.
2. Steel strip provided with a hot dip galvanized zinc alloy coating layer according to claim 1 , wherein the zinc alloy coating layer has a thickness of 3-10 μm.
3. Steel strip provided with a hot dip galvanized zinc alloy coating layer according to claim 1 , wherein the zinc alloy coating layer has a thickness of 3-8 μm.
4. Steel strip provided with a hot dip galvanized zinc alloy coating layer according to claim 1 , wherein the zinc alloy coating layer has a thickness of 3-7 μm.
5. Steel strip provided with a hot dip galvanized zinc alloy coating layer according to claim 1 , wherein the one or more additional elements are present in the zinc alloy coating, each <0.02 weight.
6. Steel strip provided with a hot dip galvanized zinc alloy coating layer according to claim 1 , wherein the one or more additional elements are present in the zinc alloy coating, each <0.01 weight %.
7. Automotive part manufactured from a steel strip according to claim 1 .
8. Steel strip provided with a hot dip galvanized zinc alloy coating layer according to claim 1 , wherein the level of Mg is 1.3-1.7%.
9. Process for producing a steel strip provided with a hot dip galvanized zinc alloy coating of claim 1 , comprising:
hot dip galvanising the steel strip with the zinc alloy coating layer, in which the coating of the steel strip is carried out in a bath of molten zinc alloy, wherein the zinc alloy consists of:
1.6-1.9 weight % aluminium,
wherein magnesium is present such that the amount of aluminium in weight % is the same as the amount of magnesium in weight % plus or minus a maximum of 0.3 weight %;
optional <0.2 weight % of one or more additional elements selected from the group consisting of Pb, Sb, Ti, Ca, Mn, Sn, La, Ce, Cr, Ni, Zr and Bi;
unavoidable impurities;
the remainder being zinc;
wherein the zinc alloy coating layer has a thickness of 3-12 μm,
wherein the silicon content in the zinc alloy layer is below 0.0010 weight %.
10. Process according to claim 7 , wherein the temperature of the bath of molten zinc is kept between 380° C. and 550° C.
11. Process according to claim 7 , wherein the temperature of the steel strip before entering the bath of molten zinc alloy is between 380° C. and 850° C.
12. Process according to claim 7 , wherein the temperature of the steel strip before entering the bath of molten zinc alloy is between the temperature of the bath of molten zinc alloy and 25° C. above the bath temperature.