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Amir Hossein Kokabi (A. H. Kokabi) Sharif University of Technology – Department of Materials Science and Engineering Address: Department of Materials Science and Engineering, Sharif University of Technology, Azadi St., Tehran, Iran E-Mail: kokabi@sharif.edu Office: 0098 21 66165214 Mobile: 0098 912 1055698

Mohammadamin Mozaffar (M. A. Mozaffar) Sharif University of Technology – Department of Materials Science and Engineering Address: No. 31, 3rd Floor, Entrance 3, Block 3, Phase 2, Ekbatan Residential Complex, Tehran, Iran E-Mail: mozaffar@alum.sharif.edu Office: 0098 21 88341861 Mobile: 0098 912 6906388

Maryam Kokabi (M. Kokabi) Sharif University of Technology – Department of Materials Science and Engineering Address: Unit 2, No. 15, East Rose St., Salimi Jahromi St., Ferdows Blvd., 2nd Sadeqiyeh Sq., Tehran, Iran E-Mail: mkokabi1003@yahoo.com Office: 0098 21 44071350 Mobile: 0098 912 2096826

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Cored Wires with different Depositions, Compositions and Applications Abstract: Cored Wires (CW) are used in a wide range of applications such as joining and hard facing. These kinds of filler metals are generally categorised in “Flux C.W”, “Self Shielded Flux C.W” and “Metal C.W”. Researches on C.Ws used for hardfacing on plane carbon steels, showed that hypo eutectic and eutectic compositions can increase the abrasion resistance. On the other hand addition of “Mn” shows some reductions in abrasion resistance and increasing in impact energy. Special coated electrodes with metal C.Ws had developed for welding of Ductile Cast Iron. This C.W can deposit weld metal same as base metal and also reduce costs in compare with E-Ni. C.Ws produced with “Ti” strip as tube and “Carbon” or “TiC” as inside powder used for hardfacing of Ti can increase the hardness, wear resistance and reduce friction coefficient. Keywords: cored wire, hardfacing, joining, wear resistance, friction coefficient Introduction: Lots of mechanical and industrial equipment such as rolling rollers, continuous casting rolls which are servicing in aggressive working environment for long times which can easily cause damage and greatly shorten their service lives1,2. One of the most economical techniques for repairing such equipment is welding. Various processes such as Gas Metal Arc Welding (GMAW), Gas Tungsten Arc Welding (GTAW), Plasma Arc Welding (PAW), Submerged Arc Welding (SAW) and Shielded Metal Arc Welding (SMAW) have been applied to hardfacing the rolls3. Flux-Cored Wires become the most rapidly developed new consumables in developed countries recent years. Alloy ingredients in the flux-cored wires can efficiently enhance the mechanical properties and wear resistance of the weld deposit3, 4. Final Chemical Composition (CC) of Weld Metal (WM) will be designated from composition of Base Metal (BM), tube, inside powder, dilution and recovery rate which can be calculated approximately by following equation (Called Dilution): %M=0.01[D(%MB)+(100-D)%ME] Where “D” is dilution, “M” is W% of element in WM, “MB” is W% of BM and “ME” is W% of Electrode. ME consists of two parts which are the W% in tube and W% in powder which is being affected by thickness and width of strip which leads to different empty spaces for filling by powder. On the other hand the final CC and mechanical properties of weld metal can change by overlapping layers, preheat and post heat. Improving the abrasion resistance with hard surfacing is related to detachment ability of materials from surface so toughness and hardness are two important mechanical properties. The most important mechanisms are Micro-Machining, Micro-Cutting and Micro-Pitting. These mechanisms have a co-operation in hypo eutectic alloys.

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In view of the above, three kinds of C.W developed and the aim of the present study is to investigate the microstructure, wear resistance and mechanical properties of the deposited metal on Common Structural Steel, S.G.C.I and Industrial Pure Titanium. Also three different procedures (GTAW, SAW, SMAW) had been used for welding. Based on the results, the new types of C.Ws would be applied to repair welding of industrial cutters, guide blades, rollers, cast iron pipes and so on5. Experiments: In all three researches a unique procedure had been used for production of C.W. This procedure consists of cleaning the strap, swaging (using swage machine) and drawing using a wire draw machine to become in “U” shape via an 8mm diameter die. After that it will be drawn through in powder and then different dies to deliver “U” shape to “O” which is containing powder. The final diameter was 3.7mm. The only difference among three researches is the material used as tube according to the weldment and powder. Part I - Common structural steel (ASTM A36) For depositing a WM with high W% of “Cr” and “C” according to the limited space of inside of the C.W tube a strip of AISI 4340 has been used. Inside powder can contain different W% of “Fe”, “FeCr”, “C” and “FeMn”. Table 1 shows the welding parameters. Code Process Travelling Speed Current (A) Voltage (V) PA11 PA12 PA14 PA24 SAW P22 P24 P32 NE88 PC64 GTAW 15 cm min-1 200 30 PC642

32 – 34 cm min-1 450 – 500 30
Table 1. Welding conditions on common structural steel (ASTM A36)

Also the role of “Mn” studied with maintaining W% of “C” and “Cr”. Same method of production has been implemented but some small changes have been made to the test plate in order to prepare impact test specimens. Welding had been done with SAW process. The shape of prepared test plate is shown in Fig 1.

Fig 1. Shape of prepared test plate for preparing CVN specimens

Abrasion test has been performed according to ASTM G65 using quartz particles (212-300 pressure load of 130 N and slipping length of 1400 m.

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In addition to abrasion test, hardness test and calculation of V% of carbide phase some other tests such as impact test (@ Room Temperature according to ASTM E23-96 (Sub-Size)) and shielding wear resistance of metal-metal (Pin-On-Disk) with rotational speed of 20 RPM (320 cm min-1) and pressure load of 50KgF has been performed. Part II – Production of C.W for welding of S.G.C.I In this part a strap of ST12 has been used as tube. A part of manufactured cored wire was used in SAW process and the rest had been divided to 30cm parts and applied for basic coats (Modified E7018 class with adding some modifications) for using in SMAW process on S.G.C.I. Table 2, Table 3 and Table 4 show welding parameters, CC of base metal and CC of used flux respectively. Parameter Procedure SAW SMAW Element W% Composition W% Fe Balance Current (A) 400 120 - 140 C 3.7 Si 2.3-2.5 Voltage (V) 30 Travelling Speed (cm min-1) 45-53 10 Mg 0.038-0.045 S