Spot welding method and craft

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Normal > one, spot welding method classifies Normal > undertakes electric welding to weldment feed, should follow following principle: ① shortens 2 times as far as possible loop length and the dimensional area that reduce loop place to include, in order to save specific power consumption; ② reduces the ferromagnetic volume that extends return as far as possible, avoid to soldering especially bulk is extended to have bigger change when different solder is nodded, solder in order to reduce voltaic wave motion, make sure each nod quality judge calm (when using labour frequency to communicate) . Normal Align=center>normal >1.

All general welder all use double-faced odd spot welding this plan. From weldment two side feed, apply to what each solder nods small-sized spare parts and large part periphery to solder. Normal >2.

Bosseyed odd spot welding is become the accessibility of a side electrode of the spare parts very poor or when 2 bigger, loop grow the spare parts too, can adopt this plan. From feed of weldment odd side, need to consider another side to add cupreous mat to regard counterforce as in order to reduce billabong fulcrum (graph 1d) . Graph 1value="12" UnitName="C">c is a special case. Normal >3.

Bosseyed double spot welding from a side feed as far as possible at the same time solder at 2 o'clock in order to improve productivity. Bosseyed feed often is put in invalid billabong phenomenon (graph 1value="12" UnitName="F">f and G) , waste electric energy, had been apart from a hour to will not solder when the dot. In certain circumstance, if the design allows, going up board two rush one narrow long breach (graph 1value="12" UnitName="F">f) but shunt electric current drops considerably. Normal >4.

1b of graph of double-faced double spot welding and J are double-faced bit doubler plan signal. Although graph 2-12b plan can be carried out on general welder, but the electric current between 2 o'clock hard equal apportionment, make sure quality is consistent at 2 o'clock harder. And because graph 1j uses means of push-pull type feed, shunt is mixed fluctuation board is inhomogenous heat the phenomenon is improved greatly, and solder dot can be decorated in aleatoric position. The place that its are not worth exclusively is to must make 2 transformer, part park weldment two side, this kind of program also calls push-pull type spot welding. The electrify of two transformer needs to undertake by polarity. Normal >5.

Much spot welding is become check the number of the solder on the spare parts is more, when mass production, often adopt plan of much spot welding in order to improve productivity. Machine of much spot welding all is special device, use means of odd side feed to see graph 1h, I for the most part, with I means more agile, 2 times loop does not get weldment measure diversionary, in the requirement higher case falls, yi Ke adopts plan of push-pull type spot welding. Use a group of transformer commonly at present at the same time solder 2 or at 4 o'clock (latter has 2 groups of 2 second return) . Machine of a many spot welding can be comprised by many transformer. Can use at the same time pressurization at the same time electrify, at the same time pressurization in group electrify and in group pressurization in group electrify 3 kinds of plan. Can choose appropriate plan according to capacity of productivity, electrified wire netting. Normal > 2, Normal > spot welding by press beforehand, solder, maintain and silent composition of 4 basic courses solders circularly, can add add program when necessary, its are basic the rule that parameter does its utmost to change along with time for electric current and report. Normal >normal > 1.

Press beforehand (F > 0, i=0) the rise that this phase includes electrode pressure and constant two parts. It is to assure when electrify electrode pressure is constant, press time to must assure beforehand, when should needing stitch welding especially, need place of movement of orgnaization of mature welder motion to need time, cannot shorten indefinitely. Normal > approachs beforehand is the voltaic channel that establishs stability, with assuring to solder the process obtains the current density with good repeatability. Right thick board or the punch part with large stiffness, conditional when can increase first during this beforehand pressure, reply to do his utmost to the report when soldering again after that, make osculatory resistor constant and not quite small, in order to improve thermal efficiency. Normal >2.

Solder (F=F ω , i=I ω ) this phase is weldment heats fused the phase that forms frit nucleus. Solder electric current but basic and changeless (point to virtual value) , yi Ke is rise gradually or rank jump rise. During this the incline to after the variation with distributinging complex experience stabilizes the temperature of weldment weld zone. At first input quantity of heat is more than be lost quantity of heat, temperature rises, form the link division of condition of high temperature plasticity, make center and air completely cut off, make sure subsequently fused metal does not oxidize, appear above all in central place after that fused area. Undertake fusing the area expands as what heat, and the plasticity carapace of its periphery (cricoid reason is shown to call plasticity annulus on metallographic test piece) also expand outwards, steady state is reached when should inputting quantity of heat and balance of be lost quantity of heat finally. Should solder when parameter is proper, can obtain dimension wave motion to be less than the fused core of 15% . Following phenomenon can produce during this: Normal > ⑴ liquid state suffers electromagnetism strength effect to produce eddy shape to flow when electrify, should inspect frit nucleus earthly record and electric extreme place is 2 extremely, its movement way is -- equatorial part by all round flow after that to ball heart flow classics is polar along outside Xiang Chi again show close shape flows. To akin metal spot welding, agitate needs to mash the oxidation film of weldment surface only can, but when heterogeneous metal spot welding, must sufficient agitate fuses with obtaining homogeneous core. If weld time is too short, agitate will produce circinate blame to all pledge inadequately frit nucleus. Normal > ⑵ splatters splatter to be able to be divided by generation period for early days and later period two kinds; By generation place can be divided for inside splatter (be in two weldment) outside mixing, splatter (weldment and electrode contact side) two kinds. Normal > early days splatters the reason of generation is roughly: Weldment surface clears not the intensity of pressure on beautiful or interface distributings serious not divide evenly, cause local current density exorbitant cause inchoate and fused, because do not have plasticity annulus,right now protection happens surely splatter. Normal > prevents the measure that early days splatters to have: Strengthen weldment to clear quality, before the attention is pressed beforehand in be opposite. Conditional when can use rise electric current gradually or increase warm-up electric current to decelerate heat speed, avoid inchoate and fused and cause splatter. Normal > later period splatters the reason of generation is: Fused core is grown and excessive, exceed electrode pressure significant action limits, break through plasticity annulus to be caused in radial thereby inside splatter, break through in axial board the surface is caused outside splatter. This kind of circumstance produces the situation that in electric current bigger, weld time grows too commonly. Usable shorten weld time and the method that reduce electric current will prevent. Normal > splatters to affect the exterior above all in outside face, the scar effect that produces next is anti-corrosive reach fatigue function. The vestiges that interior splatters falls off when move likely, if enter pipeline (like vitta) will cause jam wait for casualty. Normal > ⑶ beard is heating to fuse partly the frit nucleus brim of temperature, when certain material (be like high temperature alloy) in field trash of low melting point is more when gathering in crystal boundary to be in, this part impurity fuses above all and be squeezed to go out below the action of electrode pressure show gap. In subsequently process, the space can be filled up by liquid state metal sometimes full, dan Yike can not fill cram, appearance of body of this kind of organization calls beard on metallographic sample, and filling up full beard is just as crackle is a kind of dangerous blemish. Normal >3.

Maintain (F > 0, i=0) this phase inputs quantity of heat no longer, frit nucleus comes loose quickly hot, cooling crystallization. Crystallization process abides by caky theory. Because frit nucleus volume is minor, and clip is held between water-cooling electrode, cooling rate is very high, end in a few Zhou Neining solid commonly. Inside the plasticity carapace that because liquid state metal is in,closes, if do not have outside force, will arise when cooling systole three-dimensional pull stress, produce the limitation such as shrinkage cavity, crackle extremely easily, reason must maintain enough electrode pressure to reduce frit nucleus volume when refrigeration, compensation is contractive. Right thick board, the spare parts such as aluminium alloy and high temperature alloy hopes to increase upset force to achieve avoid shrinkage cavity, flaw. Must command the hour that increases upset power accurately at this moment. Premature will lift suddenly because of intensity of pressure because of liquid state metal make plasticity annulus is broken through, generation splatters; Already was formed too late because of caky blemish and disable. Cold electric current of this adscititious postheat delay, lower caky rate, also be helpful for preventing the generation of shrinkage cavity and crackle. Normal >4.

Silent (F > 0, i=0) this phase is soldering only use when hard steel of temper by dipping in water, insert inside hold time commonly, should solder electric current ends, frit nucleus is completely caky and after refrigeration transforms to the martensite that finish, insert again, its purpose is to improve metallographic organization. Normal > 3, spot welding solders parameter Normal > should use labour frequency when alternating current source, spot welding parameter basically has solder electric current, solder (electrify) pressure of time, electrode and electrode dimension. Normal >1.

Solder the square of quantity of heat of separate out of voltaic I ω and electric current becomes direct ratio, solder so electric current is the most sensitive to influence of solder dot function. When other parameter is changeless, be less than some to be worth frit nucleus to cannot be formed when electric current, after exceeding this value, increase frit nucleus to increase quickly along with electric current, solder dot intensity rises (graph 3 in AB paragraph) , after that because come loose,frit nucleus grows speed slow down, solder dot intensity increases slow (graph 3 in BC paragraph) , if raise electric current to bring about generation to splatter further, solder nods intensity to drop instead. So general proposal chooses not sensitive to change of frit nucleus diameter moderate electric current (BC paragraph) will solder. Normal > is in actual production, solder voltaic wave motion sometimes very big, its reason has: Normal > ① electrified wire netting or much stage welder at the same time electrify; ② ferromagnetic weldment is extended solder the change of loop; The billabong of the dot after the place before ③ is right. To soldering except the choice electric current changes relatively outside not sensitive parameter, the method that solves afore-mentioned problems is feedback control. At present the most commonly used the net controls law of compensation method, constant current and group control standard. Net pressing compensation method can be used at all all sorts of circumstances, constant current law basically is used at ② to plant circumstance, cannot use at ③ to plant circumstance, group control law is used at ① to plant only circumstance. Normal >2.

The accident of weld time affects ω of weld time T directly input caloric size, in at present wide control spot welding machine to go up for adoption the same term, weld time is (our country a week is 20ms) whole multiple. In other parameter fixed circumstance falls, the ability when only weld time exceeds some the least value begins occurrence frit nucleus, follow the growth of weld time after that, frit nucleus increases quickly first, pull cut force to also rise. When chosen voltaic moderate, increase growth of nucleus of weld time frit to slow further, gradually hasten is constant. But because heat,time grows too, the organization becomes poor, pulling force drops, can make plasticity index (σ of ductility comparing F / F τ ) drop (graph 4) . When the electric current that should choose is bigger, criterion frit nucleus is grown to the meeting after certain limit generation splatters. Normal Align=center>normal >3.

The size of pressure of electrode of electrode pressure F affects the numerical value of resistor on one hand, affect analyse caloric thereby how many, affect weldment on the other hand to electrode medicinal powder hot circumstance. Too little electrode pressure will bring about resistor to increase, analyse quantity of heat is overmuch and medicinal powder heat is poorer, cause early days to splatter; Too great electrode pressure will bring about resistor to reduce, analyse quantity of heat is little, medicinal powder heat up dimension of nucleus of good, frit to narrow, especially penetration rate drops significantly. Because this considers from energy-saving angle, should choose those who splatter not to arise pressure of the smallest electrode. This value and voltaic value are concerned, can consult in document wide for what recommend critical splatter the curve sees a picture 5. All suggest to choose at present critical splatter do not have near the curve splatter the working place inside the area. Normal >4.

Dimension of its working face refers to dimension of electrode working face next watches. Awl stage form and spherical form basically are used when spot welding at present two kinds of electrode. The size of the R of radius of the circular arc that carry a department of the D of end panel diameter of awl stage form or spherical form, how many what decided electrode and weldment interface are accumulated, when coequal electric current, it decided distributinging limits of current density size and electrode intensity of pressure. Should choose commonly bigger than expecting to obtain frit nucleus diameter the measure carrying a department that 20% working surface diameters of the left and right sides require. Next because electrode is inside water is cooling, the quantity of heat of the be lost on electrode often is as high as the input total quantity of heat of 50% , the distance change that because this carries the wave motion of ministry working face or water-cooling aperture,carries electrode surface all will be affected badly medicinal powder caloric how many, cause the wave motion of frit nucleus dimension thereby. During because this asks,diameter of working face of electrode of awl stage form is working, every increase 15% the left and right sides must repair. And water-cooling aperture end is in to exterior distance new electrode should change namely when consume comes to put 3 ~ Value="4" UnitName="mm">4mm only. Normal > spot welding, to great majority the circumstance all can choose the combination of a variety of each parameter. Normal > pursue with form or computation in the data the form is found, but before using, should make according to specific requirement adjust try solder. Normal > is reached as a result of material surface condition clear circumstance every batches are endless and identical, manufacturing workshop net is pressed state of fluctuant, equipment has change, solder to assure quality, avoid batch defective goods, often hope to take solder parameter to allow fluctuant interval beforehand. The situation that so large quantities of quantities produce, the test that interval of parameter wave motion allows when to every every batches of material, firm overhaul the equipment after must make spot welding, its trial move is as follows: Normal >1) certain quality index, for example frit nucleus diameter or only place pull the fluctuation that cuts force to be restricted. Normal >2) fixed other parameter, make some parameter (for example electric current) the relation curve with quality index, in changing fixed parameter after that one of (for example weld time) , make again solder the relation curve of electric current and quality, obtain relation curve so a group of things with common features. Normal >normal >3) use plan law as to form this 2 parameter the qualification in quality index partly again (for example electric current and time) the foliaceous curve that allows fluctuant interval. Normal > can be obtained likewise solder for example electric current and electrode pressure the foliaceous curve that wait. On the working place that aborning controls parameter inside foliaceous curve can. CNC Milling