RU2110361C1 - Method of one-sided continuously successive induction-metallurgical building up - Google Patents

Abstract

FIELD: reconditioning and reinforcing by building up of large-size parts. SUBSTANCE: method includes positioning of passive branch of induction heater over article to be built up with gap corresponding to the volume of poured charge, and active branch is positioned with gap corresponding to the thickness of built-up layer; pouring of charge onto article; moving of article relative to induction heater whose passive branch executes preliminary heating of article, and main heating up is carried out up to melting of charge by active branch of induction heater. EFFECT: higher efficiency. 2 dwg

Description

 The invention relates to mechanical engineering, in particular, to induction-metallurgical methods for the restoration and hardening of large-sized parts in all sectors of the economy.

 Known metallurgical features of induction surfacing (Induction surfacing of hard alloys / V.N. Tkachev, B.M. Fishtein, N.V. Kazintsev.- M .: Mashinostroyenie, 1970, p. 31), consisting in the fact that high-frequency currents At high temperatures and significant different chemical compositions of the interacting components, they create favorable soil for the development of diffusion processes both in the starting materials and on the mutual interfaces between the hard alloy, base metal and slag.

 However, this technology relates to the heating of loop inductors for surfacing with an internal field and is used for small products, which narrows the technological capabilities of surfacing.

 There is a method of surfacing (A.S. USSR 1516279, class B 23 K 13/00, B 39, 1989), in which the product with the mixture deposited on it is additionally exposed to laser radiation, while combining the front fronts of exposure to high-frequency current and laser, the laser radiation power is maintained at a value of 0.01-0.1 HDTV power, and the area of the laser exposure zone is set within 0.1-0.8 of the area of the exposure zone by high-frequency current.

 The disadvantage of this method is that the use of a laser provides for the operation of a slit inductor, therefore, the productivity of the process will be much lower than with one-side continuous-sequential surfacing.

 In addition, the slotted inductor does not allow surfacing of large-sized products, since the dimensions of the inductor will limit them.

 The prototype selected the induction surfacing method described in the inductor for one-side continuous-sequential surfacing with an external field (RF patent 2026610, class H 05 B 6/00, B 22 D 19/00, N 1, 1995), which consists in that the deposited part moving under the inductor is preheated with a passive coil, and the main heating is carried out under the active coil until the charge is melted.

 The disadvantage of this method of surfacing is that its technology does not provide for the regulation of the gap between the branches to ensure maximum heating intensity and the flow of active movement of the liquid metal, which significantly affects the quality of the deposited layer.

 In addition, when using the method on large surfaces (large-sized products) without a well-organized kneading process, which involves regulating the inductor capacity by the gap between the branches and observing certain gaps between the branches of the inductor and the base metal, the molten metal roller will not be sufficiently mixed, which will reduce the deposition efficiency and will narrow its technological capabilities.

 The purpose of the invention is to improve the quality of induction-metallurgical surfacing and the expansion of its technological capabilities.

где
J_i - интенсивность нагрева металла под ветвью индуктора, град/с;
J₍₁₎ - интенсивность нагрева под ветвью индуктора при зазоре, равном 1 мм, град/c;
Δ^1,4-1,5 - зазор между ветвью индуктора и основным металлом изделия мм.The goal is achieved by the fact that in the known method of induction-metallurgical surfacing, including applying the charge to the product, moving it relative to the inductor, the passive branch of which pre-heats the product, and the main heating before deoxidation of the charge is carried out under an active turn, while the passive and active branches of the inductor set under the fused product to a different amount of clearance, the passive branch is positioned on the amount of bulk charge, and the active branch of the inductor is placed on the thickness of the fused layer, the heating rate at each branch of the inductor corresponds to the relationship:

Where
J _i - the intensity of the heating of the metal under the branch of the inductor, deg / s;
J ₍₁₎ is the heating intensity under the branch of the inductor with a gap of 1 mm, deg / s;
Δ ^1.4-1.5 - the gap between the branch of the inductor and the base metal of the product mm.

 In addition, the branches of the inductor, under the influence of the electromagnetic field of high-frequency currents, create inducing currents in the surface layer of the product, the directivity of which is the same as in the roll of the molten charge, and the currents contribute to the metallurgical process of mixing liquid metal in the weld-surfacing bath, while improving deoxidation and ensuring the stability of the composition of the metal throughout the volume.

 In FIG. 1 shows a general diagram of an induction-metallurgical method; in FIG. 2 is a graph of the dependence of the heating intensity on the gap between the branches of the inductor and the base metal.

 The proposed method is implemented as follows.

 An inductor for one-way continuous sequential surfacing (Fig. 1) is placed above the product 1 in such a way that the gap h between the passive coil 2 and the product metal is equal to the thickness of the charge layer 3. The gap Δ between the active (melting) coil 4 and the base metal of the product is equal to the thickness deposited layer (b). In this case, the shape of the coil 3 should be teardrop-shaped. The distance between the branches of the inductor depends on the thickness of the guided layer, the smaller the thickness of the surfacing Δ, the closer the coils of the inductor should be brought closer together.

 After installing the inductor, the welding process begins.

 The mixture is heated for 10-30 s until it melts (liquid metal is formed).

 At the time of the appearance of liquid metal, the gap between the inductor and the base metal decreases to 2/3 of the charge charge.

 The part is moved relative to the inductor at a speed that ensures stable melting of the deposited charge.

где
J_i - интенсивность нагрева, ^oC/с;
J₍₁₎ - интенсивность нагрева при зазоре между плавящим витком индуктора и поверхностью ванны, равном 1 мм;
Δ^1,4-1,5 - зазор, обеспечивающий интенсивность нагрева.The intensity of heating the inductor in the case of heating by an external field is set due to the gap between the active coil and the base metal, and in this case it obeys the dependence:

Where
J _i - heating intensity, ^o C / s;
J ₍₁₎ —heating intensity with a gap between the melting coil of the inductor and the surface of the bath equal to 1 mm;
Δ ^1.4-1.5 - the gap providing the intensity of heating.

 Considering the graph (Fig. 2) of the dependence of the heating intensity, ceteris paribus, on the gap between the base metal and the active coil, it can be seen that the smaller the gap, the greater the heating intensity, and therefore higher heating performance.

Thus, considering the phased processes of the induction-metallurgical method, three stages can be distinguished:
I - at the time of the filing of the HDTV to the inductor under coil 2 (Fig. 1a), the flux melts and the heat transfer from the base metal to the charge layer sharply improves;
II - under the influence of the active coil (Fig. 1b), the charge layer melts and the liquid alloy is intensively mixed, which ensures the stability of the deposited alloy and good deoxidation and removal of gas and non-metallic inclusions;
III - under the influence of an electromagnetic field under an active turn 4, a liquid metal is pressed down to a value of 0.4-0.5 b, where b is the thickness of the deposited metal after crystallization (Fig. 1c).

 With the passage of alternating electric current through the active branch 4 (shaped conductor), high-frequency currents appear in the surface layer in it, where the magnetic component H is directed tangentially to the conductor. Guiding currents of the same direction appear in the part as in the roll of the molten mixture, creating conditions for the metallurgical mixing process. Magnetic components evenly distribute the particles of grains of carbide compounds in the matrix of molten metal throughout the volume of the deposited layer.

Example. Initial data for surfacing a small tooth of an automatic coupler case weighing 160 kg: surface to be hardened 420 x 50 mm; the thickness of the deposited layer is 1.5-2.0 mm; bulk density of the charge of 2.15 g / cm ³ ; specific gravity of the alloy 7.9 g / cm ³ ; the thickness of the applied layer of the mixture (theoretical) 5.7 mm; the thickness of the applied layer of the charge (specified) 5.5 mm; the gap between the base metal and the melting coil of the inductor during the process of 2.2 mm; the gap between the base metal and the heating coil of the inductor during the process of 6.0 mm; the intensity of heating is 40-60 ^o C / s.

Technological operations during surfacing of a small tooth of an automatic coupler:
The template measures the dimensions of the surface of the tooth of the automatic coupler with its subsequent cleaning and installation of the body of the automatic coupler in the clamp of the manipulator. Then check the location of the hardened surface relative to the floating branch of the inductor and the hardened surface is removed from under the inductor and the mixture is applied to it with a layer of 5.5 mm. After that, the beginning of the hardened surface under the inductor is introduced and the heating is switched on in the set mode.

After formation on the surface of the liquid bath, the gap between the inductor and the surface of said bath is reduced to 1 mm, and the heating intensity increases to 80-100 ^o C / s. Further, the hardened surface is uniformly moved under the inductor at a speed of 1.7-2.5 mm / s, providing sequential melting of the charge on the entire hardened surface.

 Then, the automatic coupling body is removed from the manipulator, abrasive cleaning of the hardened surface is performed with a grinder and the hardened tooth of the automatic coupling housing is measured with a template.

 The use of the induction-metallurgical method of surfacing allows, by adjusting the gap between the base metal and the inductor, as well as the specified intensity of heating of the latter, it is possible to intensively knead the metal under the influence of EMF. This circumstance improves the quality of surfacing, since a well-organized process (metallurgical melt) of melting complex alloyed powders improves the crystallization process, removing slags and gas inclusions on the surface of the molten bath. In this regard, the deposited metal layers have a fine grain structure and the lowest stresses in the transition zone of surfacing to the base metal due to small heat input per unit time.

 In addition, the proposed method allows to expand the technological capabilities of induction surfacing, since it has become possible to surfacing large-sized large-mass products (buffer plates, automatic couplings, rolls and screws of brick factories, working bodies of tamper machines, etc.) due to the fact that heat is removed in depth happens pretty fast.

Claims (1)

The method of one-way continuous-sequential induction-metallurgical surfacing, including applying a charge to the product, moving it relative to the inductor, the passive branch of which pre-heats the product, and the main heating until the charge is melted is carried out under an active coil, characterized in that the passive and active branches of the inductor are installed over the deposited product for different clearance sizes, the passive branch is positioned on the amount of bulk charge, and the active branch is positioned on the thickness of the weld layer, the heating rate at each branch of the inductor corresponds to the dependence

where J _i is the intensity of metal heating under the branch of the inductor, deg / s;
J ₍₁₎ - heating intensity under the branch of the inductor with a gap of 1 mm, deg / s;
Δ ^1.4-1.5 - the gap between the branch of the inductor and the base metal of the product, mm

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