Process for producing an iron-tin layer on a packaging steel substrate

Patent metadata

Field	Value
Publication number	US-9382636-B2
Application number	US-201113876961-A
Country	US
Kind code	B2
Filing date	Oct 5, 2011
Priority date	Oct 6, 2010
Publication date	Jul 5, 2016
Grant date	Jul 5, 2016

Abstract

A production process for producing an iron-tin alloy layer on a packaging steel substrate and to a substrate provided with said layer wherein one or both sides of a SR- or DR-blackplate substrate is coated with an iron-tin alloy layer which contains at least 80 weight percent (wt. %) of FeSn (50 at. % tin and 50 at. % iron).

First claim

The invention claimed is:

1. A process for producing a coated substrate for packaging applications by producing an iron-tin alloy layer on a SR- or DR-blackplate steel substrate, the process comprising the steps of:
providing a black plate steel substrate selected from the group consisting of
a recrystallisation annealed SR blackplate composed of single reduced steel substrate, or
a DR blackplate composed of double reduced steel substrate which was subjected to recrystallisation annealing between the first and second cold rolling treatment;

providing a first tin coating layer onto one or both sides of the blackplate steel substrate in a first electroplating step;
diffusion annealing the blackplate substrate provided with said first tin coating layer in a reducing gas atmosphere to an annealing temperature T a of at least 513° C. for a time t a sufficient to convert the at least the first tin coating layer into an iron-tin alloy layer to obtain an iron-tin alloy layer which contains at least 80 weight percent (wt. %) of FeSn which consists of 50 at. % tin and 50 at. % iron;
rapidly cooling the substrate with the iron-tin alloy layer in an inert, non-oxidising cooling medium, while keeping the coated substrate in a reducing or inert gas atmosphere prior to cooling, so as to obtain a robust, stable surface oxide.

2. The process for producing a coated substrate for packaging applications according to claim 1 , wherein the FeSn coating of the coated substrate is further provided with a thermoplastic polymer coating, wherein the thermoplastic polymer coating is a polymer coating system comprising one or more layers of polymer selected from the group consisting of
a) a polyester selected from the group consisting of polyethylene terephthalate polyester and polybutylene terephthalate polyester;
b) a polyolefin selected from the group consisting of polyethylene and polypropylene;
c) a copolymer of at least any two members selected from the group consisting of ethylene terephthalate, butylene terephthalate, ethylene, and propylene; and
d) blends of at least two members selected from the group consisting of polyethylene terephthalate polyester, polybutylene terephthalate polyester, polyethylene, polypropylene, and copolymers of item c).

3. The process for producing a coated substrate for packaging applications according to claim 1 , wherein the iron-tin alloy layer contains at least 85 wt. % of FeSn.

4. The process for producing a coated substrate for packaging applications according to claim 1 , wherein the rapid cooling is achieved by means of water quenching, wherein the water for quenching has a temperature between room temperature and its boiling temperature.

5. The process for producing a coated substrate for packaging applications according to claim 1 , wherein
the diffusion annealing process is performed immediately upon finishing the first tin plating step, and/or
the diffusion annealing is directly followed by rapid cooling at a cooling rate of at least 100° C./s.

6. The process for producing a coated substrate for packaging applications according to claim 1 , wherein the time at T a is at most 4 seconds.

7. The process for producing a coated substrate for packaging applications according to claim 1 , wherein the iron-tin alloy layer on at least one side of the substrate is coated with a second tin layer in a second tin plating step prior to forming the oxide, optionally followed by a flow melting step and/or a passivation treatment.

8. The process for producing a coated substrate for packaging applications according to claim 1 , wherein the iron-tin alloy layer on at least one side of the substrate is coated with at least one of a conversion layer, an organic coating and combinations thereof, wherein the organic coating comprises at least one selected from the group consisting of a thermoset lacquer, a thermoplastic single layer polymer coating, and a thermoplastic multi-layer polymer coating.

9. The process for producing a coated substrate for packaging applications according to claim 1 , wherein the annealing treatment for forming the iron-tin alloy layer is adapted to promote ageing in the SR substrate or DR substrate and/or recovery of the DR substrate.

10. The process for producing a coated substrate for packaging applications according to claim 1 , wherein
the diffusion annealing process is performed immediately upon finishing the first tin plating step, and/or
the diffusion annealing process utilises a heating rate exceeding 300° C./s in a hydrogen containing atmosphere, to a temperature between 513 and 625° C., and/or
the diffusion annealing is directly followed by rapid cooling at a cooling rate of at least 100° C./s, and
wherein the cooling is at least one selected from the group consisting of
a) performed in a reducing atmosphere comprising nitrogen atmosphere, and
b) performed by applying a hot water quench, with a minimal dissolved oxygen content, and with a water temperature of 85° C., while keeping the substrate with the iron-tin alloy layer(s) shielded from oxygen by maintaining an inert or reducing gas atmosphere, prior to quenching.

11. An apparatus for producing the strip of coated substrate for packaging applications by producing the iron-tin alloy layer on the packaging steel substrate according to the process of claim 1 , comprising:
at least one tin plating cell for providing the strip with the first tin layer onto one or both sides, optionally followed by one or more rinsing tanks for removing excess electrolyte;
followed by a heating section for diffusion annealing the first tin layer at a temperature T a of at least 513° C. for a annealing time t a sufficient to convert the first tin layer into the iron-tin alloy layer followed by a fast cooling section comprising a non-oxidising cooling medium, and wherein the heating rate of the heating section is at least 300° C./s wherein the atmosphere in the heating section optionally is a hydrogen containing atmosphere;
optionally followed by at least one further tin plating cell, the further tin plating cell optionally being preceded by a pretreatment section to activate the iron-tin alloy surface, for providing the strip with a second tin layer onto at least one side, optionally followed by one or more rinsing tanks for removing excess electrolyte;
optionally followed by a melting section for fluxing and flow melting the second tin layer;
followed by a second fast cooling section wherein the cooling rate after heating is at least 100° C./s;
optionally followed by a passivation section to apply a hexavalent-chromium-free passivation layer.

Assignees

• Portegies Zwart Ilja
• Wijenberg Jacques Hubert Olga Joseph
• Tata Steel Ijmuiden Bv

Inventors

• Portegies Zwart Ilja
• Wijenberg Jacques Hubert Olga Joseph

Classifications

• C21D8/04

  to produce plates or strips for drawing, e.g. for deep-drawing · CPC title

• C21D1/68

  Temporary coatings or embedding materials applied before or during heat treatment · CPC title

• C25D5/505 Primary

  of electroplated tin coatings, e.g. by melting · CPC title

• Y10T428/12569

  Synthetic resin · CPC title

• C25D5/48

  After-treatment of electroplated surfaces · CPC title