CN1053702C - Method of quick scan fusing hardening for surface of cast iron - Google Patents

Abstract

The present invention relates to a rapid method for the solidification and the hardening of the surfaces of cast iron parts. The method is realized by spraying a transferred arc plasma beam current to the surfaces of cast iron parts. The method comprises the following specific steps: cooling water, working gas and a direct current power supply are released; short-time high voltage is exerted between a plasma torch cathode and a plasma torch anode for breaking the working gas for forming the plasma beam current; the plasma beam current is sprayed to the surfaces of the moving cast iron parts; then, a circuit of an anode nozzle is cut off, and the surfaces of the workpieces are orderly and quickly melted and solidified under the action of the plasma beam current; finally, chilled and quenched hardening layers covering on the surfaces of the cast iron parts are obtained.

Description

A kind of method of quick scan fusing hardening for surface of cast iron

The present invention relates to a kind of method of cast iron part quick scan fusing hardening for surface, belong to the metal heat treatmet field.

Cast iron is owing to have good casting and cutting technology and an antifriction quality and cheap, is used to make wear part in a large number industrial, as machine tool guideway, slide plate, internal combustion engine cylinder jacket, bent axle, bearing shell etc.For the ease of machining, it all is the ash mouthful tissue of soft that the cast iron part blank is organized, generally no longer carry out the hardening heat processing after being machined to precision prescribed, therefore friction durability is generally lower, its reason is very easily strain cracking of cast iron part integral quenching, be unallowed in thermal treatment process, and to need attrition resistant only be upper layer, inside there is no need hardening treatment.Some case-hardened technology is used for the cast iron part surface to some extent in the industry for this reason, for example: 1.. roller electrically contacts heating quenching: this method rolls across the cast iron part surface with the water-cooled copper roller of energising, the quick local heating of big electric current of being abutted against synapsis is self-quench hardening then, obtain laser quenching hardened layer as thin as a wafer, this technological effect is not obvious; 2.. the oxy-acetylene surface hardening by flame heating: should method is simple, but technology stability is poor, energy density and temperature are lower, and the general and tissue odds of effect spares, and part deformation is big, and the danger of blast is arranged when especially improper ventilation place such as endoporus implements this technology; 3.. the rapidly solidification sclerosis of laser beam flying surface: this method is used the high-temperature laser bundle rapid scanning cast iron part surface of high-energy-density, inswept zone is added quenching structure by the white structure that rapid consolidation becomes high rigidity, hardening effect is remarkable, part deformation is little, shortcoming is to need the oil removing melanism to handle before facility investment is big, difficult in maintenance, part hardens, and environment is had pollution; 4.. the rapidly solidification sclerosis of electron beam scanning surface: this method need be implemented in vacuum vessel, and efficient is low, cost is high, accessory size is restricted.The industrial application of beam-plasma at first from cutting and spraying, develops to the surface heat process field in recent years gradually.But the plasma arc of only using non-transfer type up to now is used for the hard surfacing of medium and high carbon steel or medium high carbon steel alloy part in limited scope, promptly the steel-iron components surface does not produce fusion.When this mode is used for the wear-resisting hardened cast iron part of a large amount of needs of industry, be the ferrite matrix that soft graphite adds low carbon content owing to structure of cast iron often, hardening effect is very poor.If will make the carbon in the graphite dissolve in ferrite, just must make the surface produce rapidly solidification.Yet the plasma arc of non-transfer only constitutes the loop of electricity between the negative electrode of plasmatorch and anode, most of heat that electric arc produces is absorbed then by anode to be taken away by water coolant, the energy density of the plasma beam of anode nozzle ejection is reduced greatly, the rapidly solidification efficient that this beam-plasma is used for the cast iron part surface is extremely low, can only scan with very slow speed, consequently the accumulation of heat of part own is too much, causes part deformation overproof and scrap.Carry out quick scan fusing hardening for surface if directly utilize plasma cutting machine with the transferred-arc plasma torch, owing to processing parameters such as and gases used flow different to the requirement of structure differ bigger, anode is ablated serious, not only can not long-term stable operation, and the ablation product can pollute processed piece surface.

The object of the present invention is to provide a kind of applicant's of utilization application number is the transferred-arc plasma line that 96228948.5 utility model patent " a kind of endoporus quenches or the fusing hardening plasmatorch " is produced, and cast iron part surface quick scan fusing acquisition high rigidity spoken parts in traditional operas is added the method for curing of quenching structure.

For ease of implementing the inventive method, existing structure with above-mentioned plasmatorch is described as follows:

The structure of this plasma torch mainly is made up of cathode insulation seat, cathode copper seat, adjustable cathode and negative electrode tungsten bar, whirlwind insulating trip, anode seat, striking copper anode and O-ring seal etc., above-mentioned part is pressed in the shell by rear pressing cover and pressure pad, and the conducting rod of water-cooled tube, inlet pipe, outsourcing insulation covering is all vertical with negative electrode tungsten rod axis.Structure below in conjunction with this plasma torch of description of drawings.

Fig. 1 is the principal section figure (upper part of only drawing) of plasmatorch, the right view of Fig. 2 for cutting open along B-B line among Fig. 1, the right view of Fig. 3 for cutting open along A-A line among Fig. 1.Marginal data among each figure is as follows: (1)-inlet pipe, (2)-negative electrode conducting rod, (3)-insulation covering, (4)-and rear pressing cover, (5)-pressure pad, (6)-cathode insulation seat, (7)-and the cathode copper seat, (8)-cathode, (9)-whirlwind insulating trip, (10)-and the anode seat, (11)-negative electrode tungsten bar, (12)-striking copper anode, (13)-and O-ring seal, (14)-shell, (15)-circulating cooling water pipe, (16)-and tangential sulculus, (17)-link stopper.

In Fig. 1, inlet pipe (1), circulating cooling water pipe (15) are rotatably connected in respectively on the shell (14), the negative electrode conducting rod (2) that is surrounded by insulation thimble (3) is rotatably connected on the cathode copper seat (7), parts (1), (2), (3), (15) are parallel to each other, mutual encapsulation is (not shown) in a rigidity overcoat, and perpendicular with the axis of negative electrode tungsten bar (11).Cathode insulation seat (6), cathode copper seat (7), adjustable cathode (8) are pressed in the shell (14) by rear pressing cover (4) and pressure pad (5) with negative electrode tungsten bar (11), whirlwind insulating trip (9), anode seat (10), striking copper anode (12) and O-ring seal (13), the external peripheral surface annular knurl of rear pressing cover (4), whirlwind insulating trip (9) holds air drain processing one near the periphery of inlet pipe (15) medullary ray one side, and cuts out at least one tangential sulculus (16) (as Fig. 2 institute) in this side end face and show.Cathode insulation seat (6) and whirlwind insulating trip (9) portion are made by temperature-resistant material (as pottery, heatproof plastics etc.).Negative electrode tungsten bar (11) is shrink-fit and packs in the centre hole of cathode (8), and the cylindrical of cathode (8) is a screw thread, and there is driver flutes at the rear portion, screws in the cathode copper seat (7).The central small hole diameter of striking anode (12) is 1mm～5mm, studs with a link stopper (17) (as shown in Figure 3) in the outer loop tank.

Fig. 4 is a plasmatorch principle of work synoptic diagram.Marginal data among Fig. 4 is as follows: (18) soft output external characteristic direct supply; (19) time delay switch; (20) etc. from the torch anode; (21) plasmatorch negative electrode; (22) cast iron part; (23) high-frequency and high-voltage generator and coupling mechanism.

The method steps Fig. 4 that utilizes above-mentioned plasmatorch that quick scan fusing hardening is carried out on the cast iron part surface describes.

1. before the work negative electrode (21) of plasmatorch is received the negative pole of soft output external characteristic direct supply (18), anode nozzle (20) and cast iron part (22) connect the positive pole of power supply (18), between plasmatorch anode (20) and power supply (18), be connected in series a time delay switch (19), high-frequency and high-voltage generator of serial connection and coupling mechanism (23) are connected recirculated cooling water and working gas again between the outer circuit of anode (20) and negative electrode (21).Working gas is the organic gas of nitrogen or hydrogen or carbon containing, nitrogen boron, or the mixed gas of above-mentioned gas.

2. open water coolant and working gas when working earlier, the adjustments of gas flow is in 0.3～1 cubic metre of/hour scope, gaseous tension is in 0.005～0.5MPa scope, connect direct supply (18) again, start high-frequency and high-voltage generator (23), make the negative electrode (21) of plasmatorch and the gas ionization under the high pressure of 1000～5000V between the anode (20) become thermal plasma, after anode nozzle (20) compression, become the high-temperature plasma line of conduction, vertically be ejected into apart from anode nozzle (20) end 1mm～100mm distance, do the surface of the cast iron part (22) of relative scanning motion with plasmatorch, sweep velocity is 4mm～400mm/ second.

Because in the method, be connected in series time delay switch (19) between plasmatorch anode (20) and the power supply (18), so treat negative electrode (21) and as after conducting by beam-plasma between the workpiece (22) of second anode, time delay switch (19) cuts off the circuit between negative electrode (21) and the anode nozzle (20), discharge continually and steadily under the operating voltage state of the working current of 20A～200A and 20V～200V between negative electrode of plasmatorch (21) and the workpiece anode (22), workpiece surface is rapid successively melting and solidification under the plasma beam effect, and the final spoken parts in traditional operas that obtains covering cast iron part desired area surface adds laser quenching hardened layer.

The cast iron part of handling with the inventive method is 0.01mm～5mm through the degree of depth of this hardened layer of tentative experiment, and hardness is Hv500～Hv1500, improves 0.5～2 times before the wear resistance ratio is untreated.The sclerosis scanning strip can closely be arranged, also can be alternately or cross arrangement, and stipulate according to the service requirements of concrete cast iron part at orientation and position.

Claims (2)

1. the method for a cast iron part quick scan fusing hardening for surface, be to realize with plasmatorch with a kind of endoporus quenching or fusing hardening, the structure of this plasma torch mainly is made up of cathode insulation seat, cathode copper seat, adjustable cathode and negative electrode tungsten bar, whirlwind insulating trip, anode seat, striking copper anode and O-ring seal etc., tightly in shell, the conducting rod of water-cooled tube, inlet pipe, outsourcing insulation covering is all vertical with negative electrode tungsten rod axis by rear pressing cover and pressure pad for above-mentioned part; The feature of this method is: 1. the negative pole of before the work negative electrode (21) of plasmatorch being received soft output external characteristic direct supply (18), anode nozzle (20) and cast iron part (22) connect the positive pole of power supply (18), between plasmatorch anode (20) and power supply (18), be connected in series a time delay switch (19), high-frequency and high-voltage generator of serial connection and coupling mechanism (23) are connected recirculated cooling water and working gas again between the outer circuit of anode (20) and negative electrode (21); 2. open water coolant and working gas when working earlier, regulate airshed in 0.3-1 cubic meter/hour scope, gaseous tension is in the 0.005-0.5MPa scope, connect direct supply (18) again, start high-frequency and high-voltage generator (23), make the negative electrode (21) of plasmatorch and the gas ionization under the high pressure of 1000-5000V between the anode (20) become thermal plasma, after anode nozzle (20) compression, become the high-temperature plasma line of conduction, vertically be ejected into apart from anode nozzle (20) end 1mm-10mm distance do the surface of the cast iron part (22) of relative scanning motion with plasmatorch, sweep velocity is 4mm-400mm second.

2. the method for claim 1 is characterized in that working gas that plasmatorch is used is the organic gas of nitrogen or hydrogen or carbon containing, nitrogen, boron, or the mixed gas of above-mentioned gas.

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