tailieunhanh - FUNDAMENTALS OF METAL CASTING

Casting (process) – melt the metal, pour into a mold by gravity or other force and solidify. | 0. Alloys and Phase Diagram FUNDAMENTALS OF • Pure Metals • Alloys Substitutional – Solid solutions Solid Solution METAL CASTING • Substitutional Solid Solution (Zn/Cn and Cu/Ni) – Atomic radii is similar – Lattice type is the same 0. Phase Diagram • Interstitial Solid Solution – Smaller atoms are interstitially located among 1. Overview bigger atoms 2. Heating & Pouring – Lattice type usually does not change 3. Solidification and Cooling – Intermediate Phases – The solubility of one Interstitial element in another element is limited. Solid Solution • Metallic compounds (Fe3C) • Intermetallic compounds(Mg2Pb) 1 2 Cu-Ni Phase Diagram Pb-Sn Phase Diagram (°C) T T 1600 T 600 Liquid Eutectic Composition Temperature, °F Temperature, and Temperature 1400 500 L L+S α+L 400 α β+L 1260 362 °F β Sn 1200 300 Solid 200 α+β Substitutional Solid Alloys α 1000 100 Time Time Time Cu26% 36% 50% 62% Ni Pure Metals Pure Metals 0 Time L S Pb (lead) Sn (Tin) 3 4 Fe-C Phase Diagram Introduction • Dated back 6000 years 1800 δ • Ingot vs. Shape casting L • Polymers and ceramics are cast as well. 1400 L+θ • Issues in casting γ+L γ 1130 – Flow 1000 γ+θ – Heat Transfer – Selection of Mold Materials α 723 – Solidification- Nucleation and Growth 600 • Depending on how we control solidification, these α+θ events influence the size, shape, uniformity and 200 chemical composition of the grains. Fe1 23456 C 5 6 1 Introduction Classification • Casting (process) – melt the metal, pour into a Sand Casting mold by gravity or other force and solidify. Shell Molding Vacuum Molding • Casting (Part) Metal casting Expandable-mold Casting Expanded Polystyrene • Advantages Investment Casting – Complex geometries – external and internal Plaster-Mold Casting – Can be net-shaped or near net-shaped Solidification – Can produce very large parts Process Ceramic-Mold Casting permanent-mold Permanent-Mold Casting – Any metals Glassworking Casting – Can be mass-produced Variations of Permanent-Mold Casting – .