30 slides from Teck Resources Limited Class A's technical presentation, October 2003
Slide 1: Steel Cracking During Galvanizing - a practical approach
Steel Cracking During Galvanizing - a practical approach - Graham Poag Research Engineer Teck Cominco Product Technology Centre AGA TechForum October 2003
Slide 2: Overview
Overview Project outline History/background to the problem Overview of results to date Concurrent/future work
Slide 3: Project Outline
Project Outline Literature Search Physical Approach – PTC Practical Approach – CANMET Scientific Approach
Slide 4: Literature Survey – Not A New Phenomenon
Literature Survey – Not A New Phenomenon ASTM A-143 – “Safeguarding Against Embrittlement of Hot Dip Galvanized Structural Steel Products …” – “Conditions of Fabrication may induce a susceptibility to embrittlement in certain steels which can be accelerated by galvanizing” – This does “not imply t
Slide 5: Factors Influencing Cracking – Literature Summary
Factors Influencing Cracking – Literature Summary Hydrogen Embrittlement Strain Aging Temper Embrittlement Liquid Metal Embrittlement (LME) Steel factors – Chemistry and Carbon Equivalent – Mechanical Properties (Hardness, heat treatments, welding etc.) – Residual Stressing – Stress Raiser
Slide 6: Factors Influencing Cracking – Literature Summary cont’d
Factors Influencing Cracking – Literature Summary cont’d Galvanizing-related factors – Pickling (Hydrogen embrittlement) – Thermal Stressing » Preheating » Bath Temperature » Immersion Rate/Double Dipping – Bath Chemistry
Slide 7: Definitions
Definitions???? Embrittlement – Work Hardening LME – Liquid Metal Embrittlement LMAC – Liquid Metal Assisted Cracking
Slide 8: Project Details
Project Details PTC Practical Approach – Galvanizing susceptible HSS tubing (3” x 5” x 3/8”) » 4 steel tube manufacturers chosen based on availability – Goal was to evaluate visible cracks developed – Varying bath chemistries – Varying galvanizing parameters (T, immersion speed, preheating, fluxin
Slide 9: Steel Properties
Steel Properties Element (Wt %) Steel A Steel B Steel C Steel D Classification ASTM A500C CSA G40-21-50W ASTM A500C ASTM A500 C 0.188 0.171 0.204 0.150 Mn 0.65 0.75 0.90 0.68 P 0.011 0.011 0.012 0.009 S 0.007 0.008 0.005 0.002 Si 0.18 0.02 0.03 0.03 Cu 0.05 0.01 0.02 0.13 Ni 0.03 <0.01 0.01 0.05 Cr
Slide 10: Steel Micrographs – Inside Corner Radius
Steel Micrographs – Inside Corner Radius Steel A Steel B Steel C Steel D
Slide 11: Typical Steel Hardness at Corners
Typical Steel Hardness at Corners Microhardness Values - Black Steel 350 300 250 Vicker's Hardness Number 200 150 100 Steel A Steel B Steel C Steel D Steel A - Heat Treated (600°C) 50 0 Around Folds Inner Radius Middle Radius Outer Radius Test Location
Slide 12: Project Matrix
Project Matrix Alloys Purpose SHG Baseline PW Baseline (and effects of Pb) PW+0.05Ni Effects of: Ni PW+Bi (from 0.1 to 0.5) Effects of: Bi (3 Bi levels) PW+0.1Bi+Sn (from 0.1 to Effects of: Sn (6 Sn levels, with Bi) 1.0%) PW+0.5Sn+0.1Bi+0.05Ni Effects of: preheating, bath temperature, immersion rate
Slide 13: Pilot Line Galvanizing
| teckcominco Pilot Line Galvanizing
Slide 14: HSS Tubing Results – Steel “A”
HSS Tubing Results – Steel “A”
Slide 15: HSS Tubing Results – Steel “A”
HSS Tubing Results – Steel “A”
Slide 16: Crack Probability - Influence of Bath Composition
Percentage 0.00 20.00 40.00 60.00 80.00 100.00 120.00 SHG PW (Steel A) PW (Steel C) PW (Steel D) 0.05Ni 0.1Bi brightener level Al and carried out using Steel A 0.2Bi 0.3Bi 0.5Bi N ote: U nless specified all baths contained PW grade Z inc, 0.3Sn 0.1Bi + 0.05Sn 0.1Bi + 0.1Sn 0.1Bi + 0.15Sn 0.1Bi + 0.2
Slide 17: Crack Distribution Under Normal Operating Conditions
Percentage 0.00 20.00 40.00 60.00 80.00 100.00 120.00 SHG PW (Steel A) PW (Steel C) PW (Steel D) 0.05Ni 0.1Bi 0.2Bi brightener level A l and carried out using S teel A 0.3Bi 0.5Bi P ercentage C racks > 1" N ote: U nless specified all baths contained P W grade Z inc, 0.3Sn P ercentage S urface C rack
Slide 18: Hidden Cracking
Hidden Cracking Bath 7: SHG + Al
Slide 19: Hidden Cracks – SHG Bath Composition
Hidden Cracks – SHG Bath Composition
Slide 20: Operating Parameters
Operating Parameters Based on initial observations and the literature study several operating parameters were identified that may have an effect on crack severity – Bath Temperature – Immersion Speed – Immersion Angle – Inner radius surface quality – grinding of corners – Preheating prior to galva
Slide 21: Bath 4 Extended Trials - Operating Parameter Comparison
Percentage Cracking 0.0 0 2 0.0 0 4 0.0 0 6 0.0 0 8 0.0 0 10 0.0 0 12 0.0 0 Baseline - Bath T = 450°C, normal procedures, Steel A Baseline - Bath T = 450°C, normal procedures, Steel C Baseline - Bath T = 450°C, normal procedures, Steel D Steel A, inner corners ground b rig hten er level A l an d ca
Slide 22: Bath 4 Extended Trials - Crack Distribution by Operating Parameter
Percentage 0.00 20.00 40.00 60.00 80.00 100.00 120.00 Baseline - Bath T = 450°C, normal procedures, Steel A Baseline - Bath T = 450°C, normal procedures, Steel C Baseline - Bath T = 450°C, normal procedures, Steel D Steel A, inner corners ground brightener level Al and carried out using Steel A Stee
Slide 23: Grinding of Corners
teckcominco Grinding of Corners
Slide 24: Polishing Corners
" OD = hen fe) U D = i AL J-) a. teckcominco
Slide 25: Polished Corner Effect
Polished Corner Effect Bath 4 – Polished Corners Bath 4 – As received (Steel A) (Steel A)
Slide 26: Stress Relieving Steel A
| teckcomincc | Stress Relieving Steel A
Slide 27: Conclusions
Conclusions Cracking is not a new phenomenon – Literature shows well documented cases and studies – Literature links C equivalent and Microhardness numbers to crack susceptibility – Steel forming techniques (cold forming, welding), stress raisers, residual stressing all important factors – Thermal
Slide 28: Conclusions – Experimental
Conclusions – Experimental Bath chemistry does not appear to have an effect on the number of cracks formed (or probability of cracking) – Increasing Sn above 0.2% may influence severity, or length, of cracks formed Most galvanizing parameters did not influence crack formation Grinding the insi
Slide 29: Future Efforts/Concurrent Work
Future Efforts/Concurrent Work CANMET study Additional dipping trials – Look into alternative steel configurations » Weldments » Fabrications
Slide 30: Thank You
| teckcominco Thank You