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Weldability of Metals

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Weldability of Metals

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    2. Weldability of Metals All metals can be welded. Weldability – the ease with which a metal can be welded properly. Good weldability: Almost any process will produce acceptable welds Poor weldability: Processes used are limited and joint preparation is difficult or tedious.

    3. Weldability Involves the metallurgy of base material and filler material, the welding process, joint design, weld prep, heat treatment, and many others.

    4. Steel Classification and Identification Two primary numbering systems SAE = Society of Automotive Engineers AISI = American Iron and Steel Institute Almost identical except AISI uses a letter to identify method of manufacturing.

    5. Steel Classification and Identification Both systems use a 4 or 5 digit series to identify a steels composition. The first digit usually refers to the basic type of steel. 1xxx – Carbon 2xxx – Nickel 3xxx – Nickel Chrome 4xxx – Molybdenum 5xxx – Chromium 6xxx – Chromium Vanadium 7xxx – Tungsten 8xxx – Nickel Chromium Vanadium 9xxx – Silicomanganese

    6. Steel Classification and Identification The first two digits together indicate the series within the basic alloy group The last two digits refer to the approximate permissible range of Carbon content. Example 1020 – 1xxx Carbon Steel Xx20 20% range of Carbon AISI letters C Basic open – hearth or electric furnace steel and basic oxygen E Electric furnace alloy steel

    7. Carbon and Alloy Steels Plain Carbon Steel Steels alloyed with carbon and low concentration of silicon and manganese. Classified by the percentage carbon Low carbon Medium carbon High carbon Alloy Steels Contain specific amounts of alloying elements

    8. Low Carbon and Mild Steel Low carbon Less than 0.15% carbon Mild steel 0.15% to 0.30% carbon Both are easily welded by OFW, SMAW, GMAW To increase GTAW weldability the metal must be degassed.

    9. Medium Carbon Steel 0.30% to 0.50% carbon content Weldability increase by the various fusion processes. If more than 0.40% carbon preheating and post weld treatments are necessary. Use low hydrogen electrodes when SMAW welding.

    10. High Carbon Steel 0.50% to 0.90% carbon content Difficult to weld The weld area easily becomes very hard and brittle. To avoid preheat

    11. Tool Steel 0.8% to 1.50% carbon content Very difficult to weld Low range can be OFW but filler rod should have equivalent carbon content.

    12. High Manganese Steel 12% or more manganese 1% to 4% carbon Very tough Used for wear resistant applications

    13. Low Alloy, High Tensile Steels Popularity is increasing due to high strength to weight ratio and declining costs. Weldability is high but vary greatly, refer to supplier for specifics.

    14. Stainless Steel Consist of four groups of Alloys Austenitic Ferritic Martensitic Precipitation hardening Easy to weld with a variety of electrode types. Carbon content should be as low as possible to Improve weldability Reduce carbine precipitation When heated the chromium and carbon combine to form chromium carbide this lowers corrosion resistance.

    15. Cast Iron Very brittle 2% to 4% carbon content All but white cast iron can be welded OFW and SMAW most effective welding processes

    16. Repair Welding Can be difficult Joint preparation Base material identification Dirt / Contamination

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