University of Cebu-LM A.C. Cortez Avenue, Looc, Mandaue City College of Allied Engineering (Electronics Engineering) Report in Materials Engineering (ECE 121) Instructor Mr. Joseph Manbert Mendez
Is an alloy of iron and carbon with the carbon being restricted within certain concentration limit. It is the most prevalent metal used in engineering application due to the abundance of iron ore.
Steel is made by reducing oxide ores of iron by thermochemical reactions in a blast furnace or direct reduction vessel
Steel Refining- means making of steel from pig iron, scrap, or ore.
Two Primary Processes of steel making
Basic Oxygen Furnace
- a refractory-lined vessel that can tip too pour.
2. Electric Arc Furnace
are simply alloys of iron and carbon being the major strengthening agent.
CLASSIFICATION OF CARBON STEELS
1. Plain Carbon Steel- are the non-sulfurized carbon steel.
a. Low Carbon steel- is the steel having less than 0.30% carbon. This type of steel is used for structural shapes, wires, screw machine parts, etc .
b. Medium-carbon steel- is the steel having 0.30 to 0.70% carbon. This type of steel is used for gears, axles, etc.
c. High-carbon steel- is the steel having 0.70 to 1.40% carbon. This type of steel is used for cutting tools, knives, drills, etc.
2. Free machining steel
- resulfurized carbon steel.
Are steel that have significant addition of any element other than carbon. A steel that exceeds one or more of the following limits:
Manganese, 1.65%, silicon 0.60%, copper 0.60% is also considered as alloy steel according to the definition of the Steel Product Manual
Classification of alloy steels
- are those with less than 8.0% total alloying ingredients.
- are those with more than 8.0% total alloying ingredients .
As carbon or alloy steels capable of being hardened and tempered.
Three Main Performances criteria of tool steels are:
- refers to the ability of steel to resist softening at high performance. Another term for hot hardness is red hardness.
Tool Steel : Water-hardened W Tungsten high-speed T Shock-resisting S Mold P Oil-hardened, cold work O Molybdenum high speed M Special purpose L Hot-work H High-carbon, high-chromium D Air-hardened, medium alloy, cold-work A Description PREFIX / Group
Slightly deoxidized steels that solidify with an outer shell on the ingot that is low in impurities and very sound. These steels can be retain a good finish even after severe forming because of the surface cleanliness.
Strongly deoxidized, usually by chemical additions to melt.
Zinc coated steel products. The zinc is applied by hot dipping.
Rolled steel in the thickness range of sheet or strip.
Rolled steel primarily in the thickness range of 0.010 to 0.250 in. ( 0.25 to 6.4 mm) and with a width o 24 in. ( 610 mm) or more.
Steels with additions of sulfur, lead, selenium, or other elements in sufficient quantity that they machine more easily than untreated grades.
Steels produced from standard rimmed, capped, concast, or semikilled steel. These steels may have significant segregation and variation in composition, and they are not made to guaranteed mechanical property requirements.
Zinc-coated and heat-treated steel. There are usually paint-adhesion problems with galvanized steels. The heat treatment given to galvannealed steels creates an oxide layer that allows better paint adhesion.
Are alloy of iron, chromium and other elements that resist corrosion from many environment. For steel to qualify the stainless prefix, it must have at least 10% chromium.
Classes of stainless steel
Ferritic stainless steels
- contain chromium in the range of 16% to 20%. It has low carbon content which is less than 0.2%.
b. Martensitic stainless
- contain chromium in the range of 12% to 18%. It has a carbon as high as 1.2%.
c. Austenitic stainless
- steels have at least four major alloying elements, namely iron, chromium, carbon and nickel. The chromium content ranges 16% to 26%.
Properties of STEEL
Safety in Hardening
- This property rates tool steels on the probability or relative risk of cracking during hardening operation.
- This property is a rank of hardenability.
Size Change in Hardening
- This property refers to the net size of change that will occur in a part after hardening and tempering.
Resistance to Decarburization
- This property rates steel on their ability to resist loss of carbon at the surface during hardening.
Physical Properties of Stainless Steel
- Since these alloys are iron based, the density is about the same as carbon or low-alloy steels.
- Stainless steel are fairly poor conductors of both heat and electricity compared with carbon.
Modulus of Elasticity
- Stainless steel have tensile moduli slightly lower than those of carbon and alloy steels, 28 to 29 compared with 30(x 10 psi ) .
Steel Alloying Ingredients and its effect
1. Aluminum- aids nitriding, deoxidation, restrict grain growth, removes oxygen in steel melting. (range < 2%)
2. Boron- increase hardness (range 0.0005-0.003%)
3. Carbon- increase hardness and strength (range 0.1 to 4.0%)
4. Chromium- increase hardness and strength (range 4-18%)
5. Copper- increase atmospheric corrosion resistance, promotes tenacious oxide film (range 0.2 to 0.5%)
6. Iron Sulfide- increase brittleness.
7. Lead- added only to aid machinability (range < 0.3%)
8. Manganese- reduce brittleness, combined with sulfur (range 0.23 to 0.4%)
9. Manganese sulfide- increase machinability (range 0.08 to 0.155)
10. Molybdenum- increase dynamic and high- temperature strength and hardness, promotes grain refinement (range 0.1 to 0.55)
11. Nickel- increase toughness and hardness (range 2 to 5%)
12. Nitrogen- acts like carbon strengthening (range <0.1%)
13. Phosphorous- increase hardness and corrosion resistance (range 0.04-0.15%)
14. Silicon- increase strength (range 0.2 to 0.7%)
improves magnetic properties (range 1 to 5%)
15. Sulfur- adds machinability (range < 0.5%)
16. Titanium- fix carbon in inert particles, reduce martensitic hardness.
Steel Identification Letters prefixes and suffixes in steel identification Steel with lead additions to aid machinability xxLxx Steel with boron as an alloying element xxBxx Meaning OTHER LETTERS Steel will meet certain hardenability requirements H Meaning Suffix Composition varies from normal limits X Made in an electric furnace E Meaning Prefix
AISI- SAE Steel Designation AISI-SAE stands for ( American Iron and Steel Institute – Society of Automotive Engineers)
Resulfurized and rephosphorized carbon steel 12xx Resulfurized carbon steel 11xx Nonsulfurized carbon steel 10xx Major Constituents Series
2. Alloy steel a. Manganese b. Nickel Manganese 1.00% 15xx Manganese 1.75% 13xx Major Constituents Series Nickel 5.00% 25xx Nickel 3.50% 23xx Major Constituents Series
c. Nickel-chromium d. Molybdenum Major Constituents Series Nickel 3.50%, Chromium 1.55% 33xx Nickel 1.25%, Chromium 0.65% or 0.8% 31xx Major Constituents Series Nickel 3.50%, molybdenum 0.25% 48xx Nickel 1.80%, molybdenum 0.25% 46xx Nickel 1.80%, Chromium 0.5 to 0.8%, molybdenum 0.25% 43xx Chromium 0.5 to 0.95%, molybdenum 0.12 to 0.20% 41xx Molybdenum 0.25% 40xx
e. Chromium f. Chromium - Vanadium Major Constituents Series Chromium 1.45% 52xxx Chromium 0.80, 0.88, 0.93, 0.95 or 1.00% 51xx Chromium 0.38 or 0.40% 50xx Major Constituents Series Chromium 0.80 or 0.95 %, vanadium 0.10 or 0.15 min. 61xx
g. Multiple Alloy Major Constituents Series Nickel 0.45%, chromium 0.40%, molybdenum 0.12% 94Bxx Manganese 1.00%, nickel 0.45%, chromium .40%, molybdenum 0.12% 93xx Silicon 2.00% or 1.40% and chromium 0.7% 92xx Nickel 0.55%, chromium 0.50%, molybdenum 0.25% 87xx Nickel 0.55%, chromium 0.50%, molybdenum 0.20% 86xx
3. Heat and Corrosion- Resistant Steels Major Constituents Series Chromium (low chromium, heat-resistance) 5xx Chromium (generally not hardenable, ferritic, magnetic 4xx Chromium (hardenable, martenistic, magnetic) 4xx Chromium-nickel (nonhardenable, austenitic, nonmagnetic) 3xx Chromium-nickel-manganese (nonhardenable, austenitic, nonmagnetic) 2xx