This 7 x 5-ft., 3,500-lb. frame component for a large off-road mining truck is cast in low-alloy steel (nickel-chrome- molybdenum type) and quench and tempered for greater hardenability.


to influence the properties of steel are divided into two groups: desirable elements and undesirable elements.


Following are the desirable elements. • Carbon (C) has the largest influ- ence on determining steel alloy properties, including the hard- ness and strength levels that can


Table 1. AISI/SAE Classification System


Series Designation Type 10xx 11xx 12xx 13xx 15xx 23xx 25xx 31xx 33xx 40xx 41xx 43xx 44xx 46xx 47xx 48xx 50xx 51xx


5xxxx 61xx 81xx 86xx 87xx 88xx 92xx 93xx B


BV L


Nonresulphurized Carbon Steel Grades Resulphurized Carbon Steel Grades


Rephosphorized and Resulphurized Carbon Steel Grades Manganese 1.75%


Manganese Over 1.00 to 1.65% Nickel 3.50% Nickel 5.00%


Nickel 1.25% - Chromium 0.65% Nickel 3.50% - Chromium 1.55% Molybdenum 0.25%


Chromium 0.50 or 0.95% - Molybdenum 0.12 or 0.20% Nickel 1.80% - Chromium 0.50 to 0.80% - Molybdenum 0.25% Molybdenum 0.40 or 0.53%


Nickel 1.55 or 1.80% - Molybdenum 0.20 or 0.25% Nickel 1.05% - Chromium 0.45% - Molybdenum 0.20% Nickel 3.50% - Molybdenum 0.25% Chromium 0.28 or 0.40%


Chromium 0.80, 0.90, 0.95, 1.00 or 1.05% Carbon 1.00% - Chromium 0.50, 1.00 or 1.45%


Chromium 0.80 or 0.95% - Vanadium 0.10% or 0.15% min. Nickel 0.30 – Chromium 0.40 - Molybdenum 0.12


Nickel 0.55% - Chromium 0.50 or 0.65% - Molybdenum 0.20% Nickel 0.55% - Chromium 0.50% - Molybdenum 0.25% Nickel 0.55% - Chromium 0.50% - Molybdenum 0.35% Manganese 0.85% - Silicon 2.00%


Nickel 3.25% - Chromium 1.20% - Molybdenum 0.12% Denotes Boron Steel (e.g. 51B60)


Denotes Boron-Vanadium Steel (e.g. TS 43BV12 or TS 43BV14) Denotes Leaded Steel (e.g. 10L18)


30 | METAL CASTING DESIGN & PURCHASING | Jul/Aug 2012


be achieved. A higher carbon content increases the tensile strength and hardness levels that can be achieved while decreasing ductility and weldability. When considering alloys, it is important to remember that carbon content determines the strength of the


• Manganese (Mn) is a signifi- cant contributor to hardness, strength and hardenability (but to a lesser degree than carbon). Increasing manganese content somewhat reduces steel’s duc- tility and weldability. Man- ganese contents greater than 1.5% can increase susceptibil- ity to cracking. To avoid this problem, molybdenum (Mo) is often added in conjunction with manganese to produce manganese-molybdenum steels.


steel, but higher carbon content also makes heat treatment more difficult. Medium- to high-carbon steels (more than 0.3% by weight) can develop cracks during the heat treating or welding processes. Because of this, most non-wear resistant applications use steel with carbon levels less than 0.3%.


• Silicon (Si) increases harden- ability and strength but decreases ductility and toughness. Silicon has less influence than carbon or manganese. Silicon is often required for steel castability.


• Nickel (Ni) is used primarily to enhance the toughness of steels, especially in low-temperature uses. It increases hardenability slightly and yields small boosts in strength and hardness without decreasing ductility or toughness.


• Chromium (Cr) is added to increase hardenability and im- prove high-temperature strength, abrasion resistance, corrosion resistance and creep resistance (when a material deforms at high temperature over a long time). Ductility and toughness usually are reduced when chromium is added to the alloy, in conjunction with increases in strength. Im- proved toughness can be gained by using nickel with chromium. Chromium also makes steel more susceptible to temper embrittle- ment (brittleness that occurs when cooling after tempering). Molybdenum can be added to reduce this effect.


• Molybdenum has a marked effect on the heat treatment response of steels and is a powerful element


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