Carbon and Low Alloy Steels b

George Vander Voort

Director, Research and Technology

Buehler Ltd.

Lake Bluff, IL 60044 USA

Microstructure of wrought iron (Fe Microstructure of wrought iron (Fe 0.07% C 0.07% C 0.06% Mn 0.06% Mn 0.2% Si 0.2% Si -- 0.16% P 0.16% P 0.02% S) etched with 2% nital revealing slag stringers and ferrite (alpha) 0.02% S) etched with 2% nital revealing slag stringers and ferrite (alpha)

grains and grain boundaries. Original at 500X. grains and grain boundaries. Original at 500X.

Wrought IronWrought Iron

Electrical iron (

Surface of electrical steel specimen showing large subSurface of electrical steel specimen showing large sub--surface ferrite grains. Tint etched surface ferrite grains. Tint etched with Klemms I. The grain orientations are random (note the random distribution of with Klemms I. The grain orientations are random (note the random distribution of colored ferrite grains). Original at 100X. Viewed with crossed polars + sensitive tint.colored ferrite grains). Original at 100X. Viewed with crossed polars + sensitive tint.

Motor Lamination SteelMotor Lamination Steel

4% Picral4% Picral 2% Nital2% Nital

LowLow--carbon sheet steel (Fe carbon sheet steel (Fe 0.05% C 0.05% C 0.08% Mn 0.08% Mn 0.20% Si) etched with picral and nital. 0.20% Si) etched with picral and nital. Picral reveals the fine cementite particles and patches of pearlite. Nital reveals the ferrite Picral reveals the fine cementite particles and patches of pearlite. Nital reveals the ferrite grain boundaries and the pearlite patches, but the fine cementite particles are hard to see, grain boundaries and the pearlite patches, but the fine cementite particles are hard to see,

especially if the are at grain boundaries. Originals at 500X.especially if the are at grain boundaries. Originals at 500X.

1008 Carbon Steel 1008 Carbon Steel AsAs--RolledRolled


LowLow--carbon sheet steel etched with picral and nital. Picral reveals the fine cementite carbon sheet steel etched with picral and nital. Picral reveals the fine cementite particles and patches of pearlite. Nital reveals the ferrite grain boundaries and the pearlite particles and patches of pearlite. Nital reveals the ferrite grain boundaries and the pearlite

patches, but the fine cementite particles are hard to see, especially if the are at grain patches, but the fine cementite particles are hard to see, especially if the are at grain boundaries. Originals at 500X.boundaries. Originals at 500X.

1008 Carbon Steel 1008 Carbon Steel -- AnnealedAnnealed


Microstructure of hotMicrostructure of hot--rolled Fe rolled Fe 0.11% C 0.11% C 0.85% Mn 0.85% Mn 0.21% Si etched with picral 0.21% Si etched with picral and nital. Picral reveals the cementite and pearlite, but not the ferrite grain boundaries. and nital. Picral reveals the cementite and pearlite, but not the ferrite grain boundaries.

Nital reveals the ferrite grain boundaries and the pearlite, but the fine cementite Nital reveals the ferrite grain boundaries and the pearlite, but the fine cementite particles are difficult to see. Originals at 500X.particles are difficult to see. Originals at 500X.

1010 Carbon Steel 1010 Carbon Steel AsAs--RolledRolled

AsAs--rolled highrolled high--strength, lowstrength, low--alloy (HSLA) steel strengthened with Nb revealing a duplex alloy (HSLA) steel strengthened with Nb revealing a duplex ferrite grain size distribution. Microstructure is ferrite and pearlite. Specimen etched ferrite grain size distribution. Microstructure is ferrite and pearlite. Specimen etched sequentially with 4% picral and 2% nital. Originals at 200X (left) and 500X (right).sequentially with 4% picral and 2% nital. Originals at 200X (left) and 500X (right).

HSLA HSLA Duplex Grain StructureDuplex Grain Structure

FerriteFerrite--pearlite microstructure of 1018 carbon steel furnace cooled from 900 pearlite microstructure of 1018 carbon steel furnace cooled from 900 C (C (1650 1650 F) F) and etched with 4% picral (which does not reveal the ferrite grain boundaries). The and etched with 4% picral (which does not reveal the ferrite grain boundaries). The

hardness was 117 HV. Compare the hardness and interlamellar spacing of the air cooled hardness was 117 HV. Compare the hardness and interlamellar spacing of the air cooled (next slide) and furnace cooled specimens. Some small cementite particles can be seen.(next slide) and furnace cooled specimens. Some small cementite particles can be seen.

P

F

1018 Carbon Steel, Full Anneal1018 Carbon Steel, Full Anneal

20 m 10 m

FerriteFerrite--pearlite microstructure of 1018 carbon steel air cooled from 900 pearlite microstructure of 1018 carbon steel air cooled from 900 C C ((1650 1650 F) and etched with 4% picral (which does not reveal the ferrite grain F) and etched with 4% picral (which does not reveal the ferrite grain

boundaries). The hardness was 135 HV. boundaries). The hardness was 135 HV.

1018 Carbon Steel, Normalized1018 Carbon Steel, Normalized

10 m20 m

AsAs--quenched lowquenched low--carbon (lath) martensite and ferrite in 1018 carbon steel water quenched carbon (lath) martensite and ferrite in 1018 carbon steel water quenched from 900 from 900 C (1650 C (1650 F). The hardness was 356 HV in the center and 465 HV at the edge of F). The hardness was 356 HV in the center and 465 HV at the edge of

the bar. These pictures were from near the outer surface, but grain boundary and the bar. These pictures were from near the outer surface, but grain boundary and Widmansttten ferrite (WF) can be seen even in the outer region due to the low Widmansttten ferrite (WF) can be seen even in the outer region due to the low

hardenability of 1018. The specimen was etched with 2% nital. A manganese sulfide (S) hardenability of 1018. The specimen was etched with 2% nital. A manganese sulfide (S) particle can be seen; note the black oxide at each end of the sulfide.particle can be seen; note the black oxide at each end of the sulfide.

WF

WF

S

WF

20 m 10 m

1018 Carbon Steel, Water Quenched, Surface1018 Carbon Steel, Water Quenched, Surface

Tempered lowTempered low--carbon (lath) martensite in 1018 carbon steel water quenched from carbon (lath) martensite in 1018 carbon steel water quenched from 900 900 C (1650 C (1650 F) and tempered at 204 F) and tempered at 204 C (400 C (400 F). The hardness was 350 HV in the F). The hardness was 350 HV in the center and 436 HV at the edge of the bar. These pictures were from near the outer center and 436 HV at the edge of the bar. These pictures were from near the outer surface in an area of almost 100% martensite. The specimen was etched with 2% surface in an area of almost 100% martensite. The specimen was etched with 2%

nital.nital.

1018 Carbon Steel, Q + T (204 1018 Carbon Steel, Q + T (204 C) C) -- SurfaceSurface

20 m 10 m

Tempered low-carbon (lath) martensite and ferrite in 1018 carbon steel water quenched from 900 C (1650 F) and tempered at 204 C (400 F). The hardness was

350 HV in the center and 436 HV at the edge of the bar. These pictures were from near the center in an where there is considerable grain boundary Widmansttten

ferrite. The specimen was etched with 2% nital. Compare these images to those in the previous slide.

WF

20 m 10 m

1018 Carbon Steel, Q+T (204 1018 Carbon Steel, Q+T (204 C) C) -- CenterCenter

Tempered lowTempered low--carbon (lath) martensite in 1018 carbon steel water quenched from 900 carbon (lath) martensite in 1018 carbon steel water quenched from 900 C C (1650 (1650 F) and tempered at 538 F) and tempered at 538 C (1000 C (1000 F). The hardness was 230 HV in the center and F). The hardness was 230 HV in the center and 256 HV at the edge of the bar. These pictures were from near the outer surface in an area 256 HV at the edge of the bar. These pictures were from near the outer surface in an area

of almost 100% martensite. The specimen was etched with 2% nital.of almost 100% martensite. The specimen was etched with 2% nital.

1018 Carbon Steel, Q+T (538 1018 Carbon Steel, Q+T (538 C) C) -- SurfaceSurface

20 m 10 m

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Carbon and Low Alloy Steels b