HOT DIP HOT DIP GALVANIZING GALVANIZING

PRESENTED BYPRESENTED BY

MAHENDRA P. TATTEMAHENDRA P. TATTE

Asst.Manager Asst.Manager (operation)C.G.L.-4(operation)C.G.L.-4

CONTINUOUS / BATCH GALVANIZING

GALVANIZING: DISCOVERED BY GERMANS IN 1742

BATCH CONTINUOUS

FLUX PROCESS FLUX LESS FURNACE PROCESS

Galvalume 45 Zn+55 Al

GalfanZn-5% Al

Zn+<0.5% AlPURE ZINC

GPCC DUPLEX GA

ZINC SECTORIAL ZINC SECTORIAL CONSUMPTIONCONSUMPTION

(MARKET SHARE)(MARKET SHARE)

INDIA

Galvanising70%

Alloys, Die Casting

15%

Dry Cell10%

Chemicals5%

ZINC SECTORIAL ZINC SECTORIAL CONSUMPTIONCONSUMPTION

(MARKET SHARE)(MARKET SHARE)

WORLD

Galvanising50%

Alloys, Die Casting

30%

Dry Cell6%

Chemicals8%

Others6%

GALVANIZING INDUSTRY GALVANIZING INDUSTRY IN INDIA (ZINC USAGE)IN INDIA (ZINC USAGE)

STEEL50%

WIRE5%

GENERAL12%

TUBE33%

GALVANIZED STEEL GALVANIZED STEEL INTERNATIONAL INTERNATIONAL

SCENARIOSCENARIO

 

GALVANIZABLE STEEL

CONSUMPTION (Millions T)

GALVANIZED STEEL (Millions T)

% SHARE OF

GALVANIZING

WESTERN EUROPE 18 5.50 30.50

USA 19 2.00 10.50

AUSTRALIA 22 2.00 9.00

INDIA 11.34 0.38 3.40

HOT DIP GALVANISINGHOT DIP GALVANISING

• GALVANIZING IS THE PROCESS BY WHICH GALVANIZING IS THE PROCESS BY WHICH ZINC IS METALLURGICALLY BONDED TO ZINC IS METALLURGICALLY BONDED TO STEEL,GIVING STEEL THE MOST STEEL,GIVING STEEL THE MOST ADVANCED AND COST EFFECTIVE ANTI ADVANCED AND COST EFFECTIVE ANTI CORROSION COATING.CORROSION COATING.

• IT PROVIDES A TOUGH AND ADHERENT IT PROVIDES A TOUGH AND ADHERENT COATING WHICH SEALS THE UNDERLYING COATING WHICH SEALS THE UNDERLYING STEEL FROM CORROSION .STEEL FROM CORROSION .

• IT CORRODES SLOWLY THAN IRON (1/16IT CORRODES SLOWLY THAN IRON (1/16THTH ) )

HOT DIP GALVANISINGHOT DIP GALVANISING

GALVANIZED IRON CONTAINS GALVANIZED IRON CONTAINS ZINC ALONG WITH PRECISE QUANTITY ZINC ALONG WITH PRECISE QUANTITY OF ALUMINIUM AND OTHER ALLOYING OF ALUMINIUM AND OTHER ALLOYING ELEMENTS LIKE Pb, Sb, Sn FOR ELEMENTS LIKE Pb, Sb, Sn FOR FOLLOWING PURPOSESFOLLOWING PURPOSES

1) 1) ALUMINIUMALUMINIUM : IT IMPROVES THE : IT IMPROVES THE ADHERENCE BETWEEN THE STEEL ADHERENCE BETWEEN THE STEEL AND COATING.AND COATING.

2) 2) SnSn : FOR BETTER SHINING. : FOR BETTER SHINING.3) 3) Pb & SbPb & Sb : MAINLY ADDED TO : MAINLY ADDED TO

GENERATE FLOWERY PATTERNS GENERATE FLOWERY PATTERNS KNOWN AS SPANGLES.KNOWN AS SPANGLES.

FACTORS INFLUENCING FACTORS INFLUENCING GALVANIZINGGALVANIZING

• STEEL COMPOSITIONSTEEL COMPOSITION• ZINC CHEMISTRYZINC CHEMISTRY• BATH TEMPRATUREBATH TEMPRATURE• IMMERSION TIMEIMMERSION TIME• EXTRACTION SPEEDEXTRACTION SPEED• ANGLE OF EXTRACTIONANGLE OF EXTRACTION

ZINC COATING ZINC COATING STRUCTURESTRUCTURE

ADVANTAGES OF ADVANTAGES OF GALVANIZINGGALVANIZING

• COMPETATIVE COSTCOMPETATIVE COST• LOW LIFE TIME COSTLOW LIFE TIME COST• LONG LIFE TO FIRST MAINTAINCELONG LIFE TO FIRST MAINTAINCE• RELIABILITYRELIABILITY• SPEED OF APPLICATIONSPEED OF APPLICATION• DUAL PROTECTIONDUAL PROTECTION• FORMABILITYFORMABILITY• PAINTABILITYPAINTABILITY• WELDABILITY.WELDABILITY.

LIFE VS ZINC COATINGLIFE VS ZINC COATING

PRODUCTS IN HOT DIP PRODUCTS IN HOT DIP GALVANIZINGGALVANIZING

• GALVALUMEGALVALUME : :

IT IS A HOT DIP COATED STEEL IT IS A HOT DIP COATED STEEL WITH 55% Al, 1.5% Si , AND THE REST IS WITH 55% Al, 1.5% Si , AND THE REST IS ZINC.IT HAS A HIGH RESISTANCE TO ZINC.IT HAS A HIGH RESISTANCE TO ATMOSPHERIC CORROSION.ATMOSPHERIC CORROSION.

IT IS MAINLY PREFERRED FOR IT IS MAINLY PREFERRED FOR CONSTRUCTION INDUSTRY , IN CONSTRUCTION INDUSTRY , IN AUTOMOBILES, IN THE EXHAUST AUTOMOBILES, IN THE EXHAUST SYSTEM AND AS A STRUCTURAL SYSTEM AND AS A STRUCTURAL MEMBER.MEMBER.

PRODUCTS IN HOT DIP PRODUCTS IN HOT DIP GALVANIZINGGALVANIZING

• GALFANGALFAN:: IT IS A HOT DIP COATED STEEL IT IS A HOT DIP COATED STEEL

WITH 95% ZINC AND 5% Al HAS A GOOD WITH 95% ZINC AND 5% Al HAS A GOOD FORMABILITY AND CORROSION FORMABILITY AND CORROSION RESISTANCE.RESISTANCE.

GALVANNEALED(GA)GALVANNEALED(GA) : :IT IS A IMPROVED VERSION OF IT IS A IMPROVED VERSION OF

GALVANISED COATING,PRODUCED BY HOT GALVANISED COATING,PRODUCED BY HOT DIPPING IN ZINC BATH, FOLLOWED BY DIPPING IN ZINC BATH, FOLLOWED BY DIFFUSION ANNEALING.IT HAS A HIGHER DIFFUSION ANNEALING.IT HAS A HIGHER CORROSION RESISTANCE,BETTER CORROSION RESISTANCE,BETTER WELDABILITY AND PAINTABILITY (THAN WELDABILITY AND PAINTABILITY (THAN GI) FOR AUTOMOBILE INDUSTRY.GI) FOR AUTOMOBILE INDUSTRY.

DEVELOPMENT OF GADEVELOPMENT OF GA

IT AS AN ONLINE DIFFUSION IT AS AN ONLINE DIFFUSION PROCESS IN WHICH THE DESIRED STEEL PROCESS IN WHICH THE DESIRED STEEL GRADE COATED WITH ZINC ON BOTH THE GRADE COATED WITH ZINC ON BOTH THE SIDES BY CONTINUOUS HOT DIP PROCESS IS SIDES BY CONTINUOUS HOT DIP PROCESS IS SUBJECTED TO AN ONLINE HEAT SUBJECTED TO AN ONLINE HEAT TREATMENT(500 TO 550 DEG C).TREATMENT(500 TO 550 DEG C).

DUE TO THE DIFFUSION PROCESS DUE TO THE DIFFUSION PROCESS ZINC LAYER TRANSFORMS INTO DULL GREY ZINC LAYER TRANSFORMS INTO DULL GREY COATING.COATING.

THE IRON CONTENT IN THE THE IRON CONTENT IN THE COATING IMPROVE THE COATING IMPROVE THE GALLING,CORROSION RESISTANE AND GALLING,CORROSION RESISTANE AND WELDABILITY.WELDABILITY.

ADVANCES AND FUTURE ADVANCES AND FUTURE CHALLENGES FOR HOT CHALLENGES FOR HOT DIP GALVANIZED STEELDIP GALVANIZED STEEL

THE NOTABLE CHALLENGES IN THE FIELD OF THE NOTABLE CHALLENGES IN THE FIELD OF HOT DIP GALVANIZED STEEL AREHOT DIP GALVANIZED STEEL ARE

1.HIGH STRENGTH GI & GA (UPTO 1000 MPa YS) WITH 1.HIGH STRENGTH GI & GA (UPTO 1000 MPa YS) WITH EXCELLENT FORMABILITY.EXCELLENT FORMABILITY.

2.GI WITH HIGHER CORROSION RESISTANCE AND HENCE 2.GI WITH HIGHER CORROSION RESISTANCE AND HENCE LOWER MAINTAINCE.LOWER MAINTAINCE.

3.CHROMATE FREE PASSIVATION FOR ELECTRONIC 3.CHROMATE FREE PASSIVATION FOR ELECTRONIC APPLINCES.APPLINCES.

4.MORE STRINGENT SURFACE QUALITY FOR EXPOSED 4.MORE STRINGENT SURFACE QUALITY FOR EXPOSED AUTOMOTIVE APPLICATIONS.AUTOMOTIVE APPLICATIONS.

5.IMPROVED ROOFING MATERIAL WITH ADDED PROPERTIES 5.IMPROVED ROOFING MATERIAL WITH ADDED PROPERTIES OF HEAT & NOISE INSULATION.OF HEAT & NOISE INSULATION.

6.RECOVERY OF ZINC FROM SCRAPPED GALVANISED 6.RECOVERY OF ZINC FROM SCRAPPED GALVANISED PRODUCTS.PRODUCTS.

7.COATING WITH LESS ZINC OR ZINC ALLOYS WITH SAME OR 7.COATING WITH LESS ZINC OR ZINC ALLOYS WITH SAME OR BETTER PROPERTIES IN ORDER TO FIGHT THE BETTER PROPERTIES IN ORDER TO FIGHT THE FLACTUATING ZINC PRICE.FLACTUATING ZINC PRICE.

REASONS FOR ZINC REASONS FOR ZINC LOSSLOSS

• EXCESS ZINC COATINGEXCESS ZINC COATING• DROSS GENERATIONDROSS GENERATION• ASH FORMATIONASH FORMATION

REASONS FOR EXCESS REASONS FOR EXCESS ZINC COATINGZINC COATING

• IMPROPER CR SHAPEIMPROPER CR SHAPE• IMPROPER TENSIONIMPROPER TENSION• IMPROPER NOZZLE SETTINGIMPROPER NOZZLE SETTING

1.HEIGHT OF NOZZLE1.HEIGHT OF NOZZLE2.NOZZLE GAP2.NOZZLE GAP3.NOZZLE DISTANCE3.NOZZLE DISTANCE

• LOW AIR PRESSURE OF NOZZLE.LOW AIR PRESSURE OF NOZZLE.• HIGHER SPEEDHIGHER SPEED• LOW BATH TEMRATURELOW BATH TEMRATURE• LOW Al % IN BATHLOW Al % IN BATH

REASONS FOR EXCESS REASONS FOR EXCESS DROSS GENERATIONDROSS GENERATION

• IMPROPER CLEANING OF STRIPIMPROPER CLEANING OF STRIP• HIGH IRON FINES ON A STRIPS HIGH IRON FINES ON A STRIPS • TEMPRATURE FLACTUATIONTEMPRATURE FLACTUATION• IMPROPER Al% IN BATH.IMPROPER Al% IN BATH.• TURBULANCE CREATED IN THE BATHTURBULANCE CREATED IN THE BATH• OXIDATION OF UPPER LAYER IN OXIDATION OF UPPER LAYER IN

BATH DUE TO FREQUENT CLEANING.BATH DUE TO FREQUENT CLEANING.