COST REDUCTION IN COST REDUCTION IN HEAT TREATMENT BY USING HEAT TREATMENT BY USING

PROTECTIVE COATINGSPROTECTIVE COATINGS by by

S.P. SHENOYS.P. SHENOY - - C.E.O. and SRIKAR SHENOYSRIKAR SHENOY – G.M.

211, RAIKAR CHAMBERS, GOVANDI EAST,

MUMBAI–400 088. INDIA.

Tel. : 6797 8060 Fax : 2555 2459

Email : info@steelplantspecialities.com

Website : www.steelplantspecialities.com

PART IIntroduction.

Losses due to Oxidation.

Methods of Preventing Oxidation.

Protective Coating to Reduce Costs in HT.

PART II

Successful Case Studies.

Summary

Importance of Heat Treatment

It can either add further value to the already

value - added component, or

generate scrap

due to oxidation / scaling.

OXIDATIONOXIDATION

General reactions:General reactions:

O2

 O2

 CO2

 CO2

+ + + +

2 Fe  4 FeO  Fe 3 FeO

⇌ ⇌ ⇌ ⇌

2 FeO 2 Fe2O3

 CO + FeO Fe3O4 + CO

LOSSES DUE TO OXIDATIONLOSSES DUE TO OXIDATION

1. Loss of dimension and material.2. Deterioration of surface quality, i.e., pitting.3. Non-uniform metallurgical transformation

during hardening. 4. Lowered surface hardness and strength.5. Reduced fatigue life of heat treated product.

General practice: Removal of oxidized or decarburized layer by

machining operations after heat treatment.

PREVENTING OXIDATIONPREVENTING OXIDATION

1. Copper plating prior to heat treatment.

3. Use of molten salt bath as heating media.

4. Use of protective atmospheres.

5. Use of vacuum furnace.

6. Switching over to grades not requiring HT.

or

7. Use of protective coatings.

METALAIR

Impact of the coating on scaling mechanism.

PREVENTING OXIDATIONPREVENTING OXIDATION

Oxidation is either prevented or delayed.

COATING

Characteristics of ESPON Characteristics of ESPON Anti Scale Protective CoatingAnti Scale Protective Coating

Does not react with metal.

Does not give any toxic fume during use or during heating the coated

job.

Non-hazardous.

Economical.

Method of application: Brushing, Dipping or Spraying

PART IIPART II

Successful Case StudiesSuccessful Case Studies

Coated Billets before Hot Forging

Coated Components

before Heat Treatment

Table-1 Efficacy of Protective Coating

Type of furnace used : Box type, electric.

Test Coupon dimensions : 300mm X 100mm X 10mm

Grade of steel : AISI – 1010

Heat treatment cycle : 1000C / 4 hrs / air cool

% scale loss when not coated : 5.52

% scale loss when coated : 0.70

COATEDNOT COATED

COATED NOT COATED

Benefits of using protective coatings:Benefits of using protective coatings:

1. Elimination or minimization of post heat treatment operations like grinding, shot blasting or acid pickling.

2. Reducing decarburization – uniform hardness and mechanical properties. Increased fatigue life.

3. Preventing rejections due to quench cracking.

4. Salvaging rejected components by re-heat treatment. Increasing yield during re-working of rejected forgings.

Use of Protective Coating Use of Protective Coating

To To EEliminate Or Minimize Post Heat Treatment

Operations Like

Shot Blasting, Grinding, Or Acid Pickling.

Protective Coating to Prevent Scaling

NOT COATED COATED

CONVENTIONAL METHOD USE OF COATING

HOT FORMING

ELBOW, TEE, REDUCER, CAP, STUB END, RETURN BEND

GRADES : AISI – 304, 304L,

316, 316L,

321, 321H,

347, 347H

HOT FORMING

ELBOW, TEE, REDUCER, CAP, STUB END, RETURN BEND

GRADES : AISI – 304, 304L,

316, 316L,

321, 321H,

347, 347H

SOLUTION ANNEALING SOLUTION ANNEALING

PICKLINGPICKLING TIME IS REDUCED BY 75%

PICKLING

BUFFING

INSPECTION

SHIPPING

BUFFING CAN BE ELIMINATED IN MANY CASES. HENCE QUICKER DELIVERIES

INSPECTION

SHIPPING

BENEFITS OF USING COATING IN PROCESSING OF STAINLESS STEEL PIPE FITTINGS

Minimizing scaling during hot rolling of AISI 416 grade stainless steel.

Problem: excessive scaling during re-heating of billets mainly due to higher sulfur content.

Solution: Protective coating minimizes scaling in re-heating furnace.

Protecting Critical Areas during Heat Treatment

Coated Split Rings before Heat Treatment.

Super Duplex Stainless Steel. Investment Castings.

After Heat Treatment & Shot Blasting.

(1200 Deg. C. / 4 hrs. / water quenched)

STEEL PLATES

ANNEAL

SHOT BLAST

DESPATCH

SHOT BLAST

SHOT BLAST

ANNEAL AFTER ESPON COATING

SHOT BLAST

STEEL PLATES

DESPATCH

PRODUCTIVITY IMPROVEMENT DUE TO COATING

Above Details as confirmed by M/s. SAIL, Rourkela Steel Plant, Rourkela.

CR Sheets 4300 mm X 1100 mm X 4.5 mm

ANNEALING

950ºC/30 mins./

air-cool to room temperature

HOT LEVELLING

820ºC/60 mins.

GRINDING

FINAL THICKNESS

3.7 mm

USE PROTECTIVE COATING

SCALE PREVENTION = MATERIAL SAVING + PRODUCTIVITY IMPROVEMENT

CR Sheets

4300 mm X 1100 mm X 4 mm

ANNEALING

950ºC/30 mins./

air-cool to room temperature

HOT LEVELLING

820ºC/60 mins.

GRINDING REDUCED BY 50%

FINAL THICKNESS

3.7 mm

Preventing scaling on the inner surface of Forged Spindles

Smooth inner surface after coating and heat treating.

Use of Protective Coating Use of Protective Coating

To To Reduce Decarburization, Reduce Decarburization,

Ensure Uniform Hardness and Ensure Uniform Hardness and Increased Fatigue Life of leaf Increased Fatigue Life of leaf

springs.springs.

NOT COATED AND

HEAT TREATED.

COATED AND

HEAT TREATED.

NOT COATED AND

HEAT TREATED.

COATED AND

HEAT TREATED.

Use of Protective Coating Use of Protective Coating

To To PreventPrevent Or Minimize

Rejections due to Quench Cracking

Minimising rejections due to quench cracking:

Product: Steering knuckle

Quench crack

3% reduced to

less than 0.5%

Gear-end of crank shafts prone to quench cracks

Use of Protective Coating Use of Protective Coating

To To

Salvage rejected components by re-heat treatment

Increase yield during re-working of rejected forgings.

REJECTED COMPONENTS(HEAT TREATED)

(METALLURGICAL REASONS)

SCRAPSALVAGE BY

RE-HEAT TREATMENT USING

PROTECTIVE COATING

Re-Heat Treatment of Finish Machined Forged Spindles

Image on left shows heat treated spindles. Image on Right shows a re-heat

treated spindle. Aesthetic appeal is intact. Zero Scaling.

Heavy scaling leads to pit-marks on forgings during re-working.

Scale-pits are prevented by use of anti-scale coating during re-work. Identification numbers are intact.

SUMMARYSUMMARY

Use of protective coating has established itself as an effective technique in the area of Heat Treatment with reference to preventing scaling and decarburisation.

Thank you !

Tel. : 91-22-6797 8060 Fax : 91-22-2555 2459

Email : info@steelplantspecialities.com

Website : www.steelplantspecialities.com