Wiredrawing大中拉培訓(xùn)教材.pptVIP

Wire drawing,Vermeulen Dirk,R#KLPAA/06/197,Basic principle,To reduce the diameter of the wire: ! the volume(mass) of the wire remains the length increases the diameter is reduced,V0 = V1,V0,V1,d0,d1,L0,L1,Flow of the material,how,The deformation is done in a die,Here there is the deformation but also friction,power,Force,power,All used power is converted into: 90 to 95% to the deformation of the wire = heat 10 to 5% in residual stresses A drawing machine is huge heat exchanger Cooling is the name of the game,Deformation,Inhomogeneous deformation, shear loss, redundant work 2,Friction loss contact length,Homogenous deformation reduction,Deformation,Inhomogeneous deformation, shear loss, redundant work 2,Drawing force graph,PDFboekje RV draadtrekken.pdfmore,power,To have sufficient force to draw the wire through the die we need POWER Power : comes from electric motor How much power? Depends on: Amount of deformation(= reduction or elongation) 5.5 to 4.75 versus 5.5 to 5.00mm Strength of the wire HICA (0.80%C) versus LOCA (0.05%C) Speed 1m/sec versus 20 m/sec Friction in the die ( lubricant, coating die angle),examples,wire rod 5.5mm drawn to 4.75mm 2 m/sec LOCA (0.10%C )needs : 8.5kW HICA (0.80%C) needs :22.5kW Wire 2.00mm drawn to 1.80 20m/sec LOCA (0.10%C) needs : 16.7kW HICA (0.50%C) needs : 31.9 kW,power,9kW ? =,power,32kW =,power,Drawing 2mm LOCA from 6.5mm 15m/sec (= 54km/h or 34Miles/hour needs : 175kW net or 235 Horse power,Mastering the drawing process,Is mastering the wire temperature since a too high wire temperature destroys the lubricant film and the wire properties,Wire temperature,2. Deformation temperature (homogeneous + redundant) - % reduction - die angle - % Carbon and tensile 3. friction temperature - Contact length ( die angle bearing length) - lubricant, coating - speed,Temperature of the wire before the die = cooling of the wire on the previous pass,The temperature of the wire after the die is the sum of,1. Cooling on the capstan,Temp top : 80C(176F),Temp bottom 160C(320F),die box,5% of the wire heat Goes to the die cooling,60 to 70% of the wire heat Goes the capstan cooling,10 to 15% of the wire heat Goes to the air,10% of the wire heat Goes with the wire to the next pass,1.Cooling on the capstan,Cooling capacity of the capstan,Depends on - water flow through the capstan : litres/sec - temperature difference water in / out : delta T is related to the heat transmission of the capstan (narrow gap, only sprayers.) - capstan size : more cooling-surface - temperature of the cooling water : 15C compared to 25C - the amount of wire on the capstan = time that the wire spends on the capstan - air cooling - air flow around the wire : open capstan forced air cooling - temperature of the air around the capstan ( closed covers ! ),Example,Capstan 620mm, waterflow 1.1l/sec water temperature in 25.4C temp out 29.3 Power to cooling water : formula : waterflow l/sec delta T x specific heat water 1.1(29.3-25.4) 4.19 = 18kW This is 60 to 70% of the power that can be used on this capstan : 18/60%(70%) x 100% = 25.7 - 30 kW max Example : intermediate pass 3.40 to 3mm(.65%C) 420m/min needs 26kW - same wire on small capstan : 0.7l/sec=only 19kW cooling possible problem : wire temp will be too high,Practical examples : total machine,Capstans 400mm,Capstans 550-450mm,Wire temperatures on Koch machine,Higher speed = more power ; cooling capacity remains the same ; hence higher temperatures,Results of power and cooling measurements,Results of measurements : comparison Frigerio - Beng - measured power - in average 5.9kW to cooling =results in % Remark : no difference was made for the capstan size here,Power not good distributed : too much power on the small capstans,Wire temperatures : influence of dust extraction,6.5 LOCA to 1.05mm 1650 m/min,Frigerio : 8 pass 560 others 460 Jupiter : 10 pass 550 others 450,Heat is accumulated in the wire,Wire temperatures : no dust extraction,Temperatures higher if dust extraction is switched of,Influence of forced air cooling,Influence of air cooling on mech. properties,Conclusions about capstan cooling,If used power is higher then cooling capacity the heat is accumulated into the wire Hence drawing problems + poor mechanical properties Therefore die series should be calculated taken into account the cooling capacity of the capstans. Smaller capstans have less cooling capacity Damaged water seals in the narrow gap system, incrustations etc. reduce the cooling capacity Its important to maintain the cooling in a good condition,Comments on cooling,Installed electrical motor power has to be in accordance to cooling capacity of the capstan : a 61kW motor on a 620mm capstan makes no sense. Motor will be used in the worst conditions = more losses. Cooling capacity can be increased by extra air cooling up to 15% Measuring the wire temperature on the capstans with an IR meter is a fast and cheap control, which should be done on a regular base and always in case of drawing problems.,2. Master the deformation temperature,Reductions : 30% for LOCA 15 to 25% for HICA Tapered reductions = equal power per pass Correct die angles , - 25% reduction with 6 - or 10% reduction with 20 gives excessive (waste) power (= heat),example,2.00mm from 6.5mm rod LOCA 0.10%C 15m/sec,3. Heat by friction,The wire is touching the die surface Hence friction=heat To reduce this friction : a lubricant is used Purpose is to separate the two surfaces,Master the friction = lubrication,For wire drawing min 1 g/kg lubricant film is needed to have a good separation, lubrication : this for widia dies e.g. 4.75mm needs min 9.3 g/m 1.00mm needs min 2 g/m As a rule of thumb : necessary g/m = 2 wire for diamond dies 0.5 g/kg is sufficient This lubricant film has to be composed of 50% FA and 50% of hard components Its also necessary to have a good adhesion to the wire surface,Composition of the lubricant film,Hard components Can be the coating : lime, borax, Zn-phosphate (= a good adherence) Can be present in the drawing soap Called : fillers Lubrication components Have to come 100% from the drawing soap This is called the Fatty Acids,Soaps,2 kind of soaps are used Na-soaps: often colored - rounded forms less dust Ca-soaps: rarely colored coarse forms dusty in handling,properties of drawing soaps,Where to use what soap,Na soap - high %FA , low% fillers = in combination with coating or after some passes Ca soap ! Cooling is important : if soap burns nothing remains Water soluble ( preferred for degreasing ) Ca soap - low % FA, high% fillers = no coating necessary but low amount of FA will result in higher wear and ruptures if cooling fails : still the fillers are present drawing is still possible but high wear - also advised for galvanised wires Not degreasable,Graphs not ok,Graph not ok,Graph Ok,Diamond die,Where to use what soap,Na soap - high %FA , low% fillers = in combination with coating or after some passes Ca soap ! Cooling is important : if soap burns nothing remains Water soluble ( preferred for degreasing ) Ca soap - low % FA, high% fillers = no coating necessary but low amount of FA will result in higher wear and ruptures if cooling fails : still the fillers are present drawing is still possible but high wear - also advised for galvanised wires Not degreasable,Maintaining a good lubrication film,Start from the first pass with 1g/kg master the cooling of the wire Avoid mechanical contacts which damage the lubricant film Use the right soaps Keep the dies in a good condition worn dies destroy the lubricant film + create defects on the wire surface whic