MMET 207 Exam II mia carrola

The first two digits of the SAE numbering system indicate _____

alloying element if present

The last two digits of four, or last three of five indicate ____

nominal carbon content in points

10

plain carbon steel

11

resulfurized steel

41 Chemistry

Carbon, Manganese, Chromium, Molybdenum

43 Chemistry

Carbon, Manganese, Nickel, Chromium, Molybdenum

Prefix E

made in electric arc furnace

Prefix X

composition varies from normal (also referred to as modified)

Suffix H

indicates steel will meet certain hardenability requirements

If a steel meets certain hardenability requirements, that means ____

carbon and alloy contents are at the high end of the acceptable range

B

Indicated steel with boron as an alloying element

L

indicates steel with lead added-improves machinability-should never be welded

What is hot finished steel?

it is worked at elevated temperature until its final form

What is cold finished steel?

it is worked at room temperature in the last stages of finishing

Is cold or hot finished more expensive?

Cold finished

What are the characteristics of hot finished steel?

-poor surface finish

-looser dimensional control

What are the characteristics of cold finished steel?

-higher cost

-less stable-warps when welding

Hardenability

the ability to form martensite

What limits the hardness of martensite?

carbon content

What helps to facilitate the formation of martensite?

alloying elements

Aluminum

-typically less than 2%

-restricts grain growth

-removes oxygen in steel making

-aids nitriding

Sulfur

-typically less than 0.5%

-adds machinability

-significantly reduces weldability, ductility, and toughness

Phosphorous

-typically less than 0.5%

-adds machinability

-significantly reduces weldability, ductility, toughness

Chromium

-typically ranges 0.3-4%

-increases resistance to corrosion and oxidation

-significantly increases hardenability

-increases high temperature strength

-can combine to form chromium carbides

Nickel

-typically 0.3-5%

-promotes an autenitic structure

-increases hardenability

-increases toughness

Copper

-typically 0.2-0.5%

-is not removed well during steel recycling

-too much will lower impact strength

-promotes tencaious oxide film to aid atmospheric corrosion resistance

Manganese

-typical range is 0.3-2%

-increases hardenability

-combines with sulfur to reduce its adverse effects-manganese sulfides

-promotes austenitic structure

Silicon

-typical range is 0.2-2.5%

-removes oxygen in steelmaking

-improves toughness

-increases hardenability

-improves fluidity of molten metal

Molybdenum

-typically 0.1-0.5%

-promotes grain refinement

-increases hardenability

-improves high-temperature strength

Vanadium

-typically 0.1-0.3%

-promotes grain refinement

-increase hardenability

-forms vanadium carbides

Boron

-typically small amounts:0.0005-0.003%

-increases hardenability

Lead

-less than 0,3%

-added only to aid machinability

-health risks from dust

Nitrogen

-typically less than 0,1%

-acts like carbon in strengthening