Steel cord with a brass coating enriched with iron particles

Patent metadata

Field	Value
Publication number	US-2022112656-A1
Application number	US-202017423673-A
Country	US
Kind code	A1
Filing date	Jan 27, 2020
Priority date	Jan 31, 2019
Publication date	Apr 14, 2022
Grant date	—

Abstract

A steel cord that is suitable for reinforcing rubber articles such as tires. The inventive steel cord enables to completely eliminate the presence of cobalt in a tire when combined with the proper cobalt free compound. Advantageously the steel cord adheres equally well to rubbers containing organic cobalt salts. The inventive wire is different from prior art steel cords in that the brass coating now comprises iron particles. The iron particles have a size between 10 nm and 10 000 nm. The presence of iron mitigates the adhesion retention loss of the rubber to steel cord bond in a hot and humid environment. It is a further advantage that the inventive steel cord does not contain any intentionally added cobalt thereby contributing to the elimination of harmful substances in the production area as well as the environment.

First claim

1 . A steel cord comprising one or more filaments,
said filaments comprising a steel filamentary substrate and a coating partly or totally covering said steel filamentary substrate, said coating comprising brass consisting of copper and zinc, said coating being enriched with iron, wherein said iron is present as particles in said brass, said particles having a size between 10 and 10 000 nanometer.

2 . The steel cord according to claim 1 wherein said particles have a size between 20 and 5000 nanometer.

3 . The steel cord according to claim 1 wherein said brass comprises at least 63% of copper by mass, the remainder being zinc.

4 . The steel cord according to claim 1 wherein the amount of iron in said coating is greater than or equal to 1% in mass and is smaller than 10% in mass compared to the total mass of brass and iron.

5 . The steel cord according to claim 4 wherein the amount of iron in said coating is greater than or equal to 3% in mass and is smaller than 9% in mass compared to the total mass of brass and iron.

6 . The steel cord according to claim 1 wherein said coating is substantially free of zinc iron alloy.

7 . The steel cord according to claim 1 wherein the amount of phosphorous present at the surface of said filament is P s and wherein the amount of iron present at the surface of said filament is Fe s , said P s and Fe s being determined by the P s and Fe s Procedure 3 as defined in the description and expressed in milligram per square meter, said P s being smaller than or equal to 4 mg/m 2 and larger than zero.

8 . The steel cord according to claim 7 wherein the amount of iron present at the surface Fe s is larger than or equal to 30 mg/m 2 .

9 . The steel cord according to claim 7 wherein the ratio of Fe s over P s is larger than 27.

10 . The steel cord according to claim 7 wherein the surface coating weight SCW is the sum of the mass of brass and iron present in said coating per unit of surface area, said coating weight being expressed in grams per square meter wherein the ratio of Fe s over the product of P s and coating weight SCW is larger than 13.

11 . The steel cord according to claim 1 wherein said steel cord consists of a single filament.

12 . A rubber product comprising vulcanized rubber reinforced with a steel cord according to claim 1 wherein said rubber product is one out of the group consisting of tire, passenger car tire, truck tire, van tire, off-the-road tire, hose, hydraulic hose, belt, synchronous belt, conveyor belt, elevator belt.

13 . The rubber product according to claim 12 wherein said vulcanized rubber is substantially free of cobalt.

14 . The use of the steel cord according to claim 1 for the reinforcement of a rubber product.

15 . A method to produce a filament of a steel cord according to claim 1 comprising the following steps:
a. Providing an intermediate steel wire having an intermediate diameter;
b. Electrolytically coating said intermediate steel wire with copper, iron and zinc;
c. Subjecting said copper-iron-zinc coated intermediate steel wire to a heat treatment to diffuse the zinc into the copper at a temperature of at least 420° C. and below 530° C. resulting in an intermediate steel wire with a brass coating enriched with iron particles;
d. Optionally removing the zinc oxide and iron oxide from the surface of said intermediate steel wire with a brass coating enriched with iron particles by immersion in an acid bath;
e. Subjecting the intermediate steel wire with a brass coating enriched with iron particles to a wet wire drawing operation thereby obtaining said filament;

wherein by the wet wire drawing operation the iron particles as present on the intermediate steel wire with a brass coating enriched with iron particles are diminished to a size of below 10 000 nm and larger than 10 nm.

16 . The method according to claim 15 wherein the step:
b. Electrolytically coating said intermediate steel wire with copper, iron and zinc;
is performed by the following substeps of:
b1. Electrolytically coating said intermediate wire with copper;
b2. Electrolytically coating the copper coated intermediate wire with iron;
b3. Electrolytically coating the copper-iron coated intermediate wire with zinc;

17 . The method according to claim 16 wherein the step:
b2. Electrolytic coating said copper coated intermediate steel wire with iron;
is performed in any one out of the group consisting of following electrolytic plating solutions:
Ferrous chloride solutions;
Ferrous sulfate solutions;
Ferrous ammonium sulfate solutions;
Ferrous fluoroborate solutions;
Ferrous sulfamate solutions;
Mixed sulfate-chloride baths

18 . The method according to claim 15 where in the step of:
e. Subjecting the intermediate steel wire with a brass coating enriched with iron particles to a wet wire drawing operation;

wet wire drawing is performed to a true elongation of at least 3.5.

19 . The method according to claim 15 wherein the step of:
e. Subjecting the intermediates steel wire with a brass coating enriched with iron particles to a wet wire drawing operation;

wet wire drawing is performed by means of one or more dies comprising diamond.

Assignees

• Bekaert Sa Nv

Inventors

• Wang Baoxing
• Tang Yunfang
• Hamon Yohann

Classifications

• C25D3/20

  of iron · CPC title

• C25D7/0607 Primary

  Wires · CPC title

• C25D5/10

  Electroplating with more than one layer of the same or of different metals (for bearings C25D7/10) · CPC title

• D07B2205/3089

  Brass, i.e. copper (Cu) and zinc (Zn) alloys · CPC title

• C22C9/04

  with zinc as the next major constituent · CPC title