SE453577B - HARD WELDED PART, METHOD OF HARD WELDING AND USE OF THE HARD WELDED PART - Google Patents

Description

15 20 25 30 35 453 577 melting zone.

As those skilled in the art know, micro and macro defects in the melting zone between the molten layer and the part are unavoidable under all kinds of welding conditions. Tension stresses arise in the part under external load, which under most load conditions for the parts, such as shafts, reach their maximum on the surface, micro-defects occur in the melting zone in the form of micro-cracks. These micro-cracks also occur during stress annealing or under the influence of temperature variations during the work on the part that leads to the development of stress cracks.

Under the influence of dynamic load, these micro-cracks grow and cause fatigue fractures in the hard-welded, ie cemented carbide part. Under such loads, further necrosis cracking can: the molten layer cause flaking where the layer is bonded to the part. As a result of a delicate intermediate layer between the part and the welded layer, a stress jump occurs at the same time where the stresses pass from the part to the coating. This results in shear forces appearing in the coating where it is connected to the surface of the part. At the same time as this takes place and the intermediate layer between the part and the welded coating is soft, these forces have similar directions and are the reason why the coating is sheared off. The mentioned factors become even more pronounced due to considerable residual stresses that develop in detail after the hard welding. These stresses in the melting zone are the most frequent cause of tensile stresses.

Due to the known technology, a manufacturing method for hard-welded parts is also known, which includes a significant reduction of residual stresses. According to this method, after multilayer hard welding on a detail by arc welding and subsequent mechanical treatment thereof, a temperature treatment takes place (Frumin, I.I., "Automatic Hard-Facing by Arc Welding", Metallurgized Publishing House, 1961, page 374). In this known method, however, the application of the cemented carbide coating by arc welding takes place in the same way as in the previously mentioned methods, and thus there is a soft intermediate layer between the part and the welded coating as well as a melting zone with minimal thickness. As a result, the strength of such a detail is affected by all the above-mentioned factors which lead to a reduction in its durability.

The main object of the present invention is to provide a manufacturing method for hard-welded parts and parts manufactured according to this method, according to which a special melting zone between the part and the molten layer is created by welding a special zone when welding the first layer. arising in this zone does not affect the strength of the final product.

Based on this main object, a manufacturing method for hard-welded parts is proposed which comprises applying a multi-layer welded coating to a part by arc welding with a consumable electrode, mechanical treatment and heat treatment thereof, wherein according to the present invention the first layer is applied to provide regular, continuous in succession in at least one direction successively projecting from the base of the layer to the metal of the part, and the consumable electrode used for producing this layer is made of metal, the coefficient of thermal expansion of which is lower than that of the metal of the part.

The product finished according to the present process, which constitutes a hard-welded part according to the invention, has an intermediate layer in the melting zone between the part and the coating with such relief shape with depressions and projections which continuously change at least in the direction of action of the most dangerous forces arising in the part. in its use. In the same direction, residual compressive forces extend at least within the thickness range of the melting zone.

Residual compressive forces are transmitted to the melting zone between the part and the coating during the heat treatment of the product. Their origin is due to the fact that the coefficient of thermal expansion in the coating material in the melting zone is lower than for the metal of the part on which the welded coating is applied. Due to the relief structure of the intermediate layer between the part and the welded coating, a soft change in the coefficient of thermal expansion occurs in the melting zone. As a result, there is a sharp reduction in the thermal stresses obtained especially in the heat treatment. Due to the compressive forces in the melting zone, the present macro- and micro-defects can not lead to the appearance of micro-cracks during the compression stage. Furthermore, residual compressive forces significantly increase the strength of the finished product in the melting zone, since tensile stresses occurring under the influence of an external force are reduced by the sum of these residual compressive forces. Assuming the remaining compression forces higher values, this can lead to the metal in the end product not being exposed to tensile stresses in this zone at all during the work.

The relief structure in the intermediate layer between the part and the coating by penetrating the base of the first layer into the metal of the part eliminates the stress jump when the stresses pass from the metal of the part to the coating.

This causes a significant reduction in the shear forces in the coating where it is bonded to the surface of the part despite the fact that the coefficients of temperature expansion in the metal of the part and in the first weld layer are different. In particular, the pronounced relief structure in the intermediate layer between the part and the welded layer in the form of alternating depressions and protrusions causes a continuous change in the direction of action of the shear forces, which affect the coating layer in its connection to the part, which increases the bond. and the detail. Taken together, all of these factors favor the increase in strength - including fatigue resistance - of hard welded parts made in accordance with the present invention over parts made by known methods.

Protrusions from the base of the first layer towards the metal part can be achieved by mechanical surface treatment of the part to be welded hard and by subsequent application of metal from a consumable electrode in the depressions formed in this mechanical treatment. In this respect, several different types of mechanical treatment are possible such as cutting or pressing. The depressions can also have different shapes such as grooves, round points and the like.

However, these depressions should continuously follow one another and not be too deep to produce protruding portions only from the base of the first welded layer, while its outside should be relatively smooth.

According to a suitable embodiment of the present invention in the manufacture of hard-welded parts, which have a special degree of formation of macro- and micro-defects and with temperature stresses during the course of the hard-weld coating, after mechanical treatment the first layer can be welded while penetrating its base under a electric arc operating conditions, which is not associated with any far-reaching heat generation.

The penetration of the base of the first layer into the metal part according to the present invention can be effected by welding this layer with a consumable electrode in the form of a wire and with welding strands extending in one direction. Their relative distances in the welding layer are selected in accordance with the utilization coefficient of their projecting surface parts. As is known to those skilled in the art, a relative strand distance in a welded layer represents a relationship between the distance between the strands and their width. A coefficient of utilization of their projecting surface portions with respect to these strands represents a ratio between the actual surface of their projecting parts and the surface of a rectangle, one side of which is equal to the width of the weld string while its other side is equal to the height of the projecting portion of the strands.

This embodiment of the present invention without any mechanical pretreatment provides a design of the first welding layer on the surface of the part with a relatively smooth outside, the portions projecting from its base in the metal of the part having a corrugated intermediate layer structure between the part and the welded coating. Such an embodiment of the invention is the most technologically simple and can be easily realized with known technology. However, such an embodiment is expedient only for parts in which the most risky forces during the work act in a single direction. According to this embodiment, in which the first welded layer is applied with structures projecting from its base into the metal of the part, the welding strands are arranged transversely to the direction of action of said forces.

The penetration of the first layer base into the metal of the part according to the present invention can be achieved by welding this layer with a wire electrode with crosswise arrangement of the welding strands and with a relative distance between welding strands with the same direction in the layer corresponding to the utilization coefficient of their projecting surface parts.

This embodiment of the invention, like the previously mentioned one without any mechanical pretreatment, provides a formation of the first welding layer on the surface of the part with a relatively smooth outside and with insertion of its base in the metal of the part which continuously follows one another. At the same time, the cross-arrangement of the welding strands provides a more developed intermediate layer surface between the part and the welded coating with continuously alternating depressions and protrusions in all directions. Therefore, such an embodiment is recommended for parts that are exposed to complex loads where hazardous forces act in different directions.

From the base of the first layer according to the present invention protruding structures in the metal of the part can be achieved by spot welding application on this layer with a center distance between adjacent welding points between 0.30 to 0.68 of the diameter of these points.

Such an embodiment of the invention makes it possible, like the previously mentioned ones, without any mechanical pretreatment to obtain a developed intermediate layer surface between the part and the layer applied thereon by the welding, whereby spot welding results in the most prominent surface of this intermediate layer.

Overlay spot welds can be achieved by feeding a wire-shaped consumable electrode to the surface of the part with periodically varying speed but constant relative speed of movement between the electrode and the surface of the part and with constant energy supply values. Such a method of spot welding involves step feeding of a wire electrode to the surface of the part, which can preferably be achieved by using an electric stepping motor or specially designed feed rollers for wire electrode feeding.

Overlay spot welding can be carried out with periodic variation of the energy supply with continuous feeding of a consumable wire electrode to the surface of the part, its movement along said surface taking place at a constant relative speed. Such an embodiment of spot welding can be suitable if an eye welding control system is used which can be combined with a system for periodic variation of the energy supply. With any method of application of the first welding layer to the surface of the part according to the present invention, it is suitable that the welding of the layer with a consumable wire electrode is performed in a few operations. When producing protrusions from the first layer base in the metal of the part, overlay welding allows in several rounds a reduction of undesirable effects due to greater heat generation under hard weld application conditions when forming the protrusions from the first layer base, temperature loads and the phase structure of the detail metal. In this case, the number of rounds is chosen so as to achieve an optimum with respect to the temperature conditions of the surface coating, taking into account economically advantageous hard weld coating productivity.

In addition, in each method of applying the first layer to the surface of the part according to the invention it is advisable to weld other metal layers after the first layer applied directly to the surface of the part under conditions which cause the least possible thermal effect of the melting zone between the part metal and the first layer. This makes it possible to obtain a relief structure on the intermediate layer between the part and the first welding layer applied thereto. 10 15 20 25 30 35 453 577 8 This can be achieved by reducing the relative distance between the welding strands in the layer, by reducing the welding current, by using a strip-like consumption electrode or powder wire or by other means.

A hard welded part according to the present invention may have different combinations of metals in the part and the welding layer arranged thereon. F When manufacturing parts of carbon steel or low-alloy perlite structural steel with a corrosion-resistant coating, it is appropriate that at least the layer directly welded to the surface of the part on a part is selected in high-chromium-grade steel. Details of carbon steel or low-alloy perlite structural steel are widely used in machines and mechanical devices such as power transmission elements and those under dynamic loading. In comparison with carbon steels or low-alloy perlite structural steels, steels with a high chromium content have a lower coefficient of thermal expansion which makes it possible to achieve high fatigue resistance against relatively high compressive forces both in the melting zone between the part and the overlay weld and in the overlay weld itself. At the same time, steels with a high chromium content are characterized by high strength and plasticity, and therefore a product treated according to the invention has a long service life. The welded layers that follow the high chromium steel layer can be made of any suitable metal including the same high chromium steel that the first layer consists of and that has good anticorrosive properties.

The overlay weld according to the present invention on the part may comprise layers of different metals. In this case, the intermediate layer in the melting zones between such layers shall be given such a structure that it forms an even transition between coefficients of thermal expansion through the thickness of the weld. In the manufacture of parts of carbon steel or low-alloy perlite structural steel with welds where the first layer consists of high chromium steel is recommended that additional layers of austenitic stainless steel are welded to this layer. In this case, the outer layer of austenitic stainless steel provides corrosion protection for such parts.

In the manufacture of such parts, after application of the stainless austenitic steel layer, it is suitable to roll the hard welded surface of the part to compress the austenitic stainless steel layers. In the case of parts according to the invention which have plain bearing elements, the latter should be arranged on the overlay welds arranged on the part in question. Sliding bearing elements can be crimped, welded or otherwise fixed to the overlay weld. In the manufacture of a part according to the invention, the need for a soft connection between the plain bearing support elements and the main body of the part is eliminated, since the stress concentration along the edges of the plain bearing elements has no effect on the strength of the product, considered as a unit.

At the same time, said embodiment enables the use of different metals for the overlay weld and the plain bearing support elements, which ensures optimal properties regarding the overlay weld and the bearing elements.

It is convenient to manufacture the plain bearing elements as a bearing weld of bearing metal which is welded to the weld applied to the part. Such an embodiment makes it possible to reduce the cost of bearing metal and to harmonize the technological manufacturing process for such products.

The present invention, which relates to hard-welded parts, can be used to great advantage for ship propeller shafts with a high metal content, the operating conditions of which are associated with the transmission of high dynamic forces and which are exposed to corrosive seawater.

The features and advantages of the present invention are explained in more detail in connection with a detailed description of their embodiments with reference to the accompanying drawings. In these: Fig. 1 shows a welding machine by means of which an overlay weld is applied to a shaft, according to the present invention; Fig. 2 (a-d) shows successive steps in the application of the first layer to the shaft in combination with mechanical processing, according to the invention; Fig. 3 shows the axis with the first layer applied to it after the operations shown in Figs. 2a - d have been performed, on a larger scale compared with Fig. 2; Fig. 4 is a diagram showing the distribution of residual stresses across the cross-section of the hard-welded shaft made in accordance with the present invention; Fig. 5 (a, b) shows the application of the first layer to the shaft in a helical working operation in which the welding strands in the layer have the same direction; Fig. 6 shows a shaft machined according to the invention with corrosion-resistant coating and layers of sliding metal on the bearing seats; Fig. 7 the application of the first layer to the shaft in a few helices with the same direction; Fig. 8 shows the application of the first layer to the shaft in accordance with the present invention with cross-arranged helices; Fig. 9 is a welding wire feed device for use in spot welding application of the first layer according to the invention; Fig. 10 shows the application of the first layer to the shaft by spot welding thereon according to the invention and Fig. 11 shows a hard-welded shaft whose welding pads according to the invention are built up of different metals.

The following describes the best ways of practicing the invention.

The present invention can be used to manufacture a wide variety of hard welded parts having different shapes and functions. However, since the present invention can be used with the greatest advantage in the manufacture of shafts, in particular ship propeller shafts and their bearing bushings, the following examples relate to parts of this kind.

Machining methods for other parts are in principle of the same kind as described in the examples, and the present differences mainly relate to the location of the part being treated and the kind of relative movement between a part and a machining tool. At the same time, the examples described below make it possible to explain the invention clearly and completely and to show the best embodiments of the invention.

Example 1 This example relates to the manufacture of a shaft with 250 10 15 20 25 30 35 453 577 ll m diameter and 4,000 m length to be coated with a 5 mm thick corrosion-resistant layer. The shaft is made of perlite structural carbon steel with a carbon content of about 0.3% which is industrially manufactured in the Soviet Union under the trade name Steel 30. This steel has a coefficient of thermal expansion of 14 x 10-6 l / ° C. More detailed data for this steel as well as for other steels are mentioned in the description of the embodiments represented in Table 1 later in the description.

To be coated with cemented carbide, the shaft 1 is positioned in a welding machine (Fig. 1) whose support 2 is provided with a welding head 3 for feeding a welding wire 4, an induction heating element 5 and a tool holder 6.

When the shaft 1 has been forged and set up in the lathe, its surface is roughly turned to a diameter for hard welding.

Then a parallel triangular thread cutter 7 is fixed in the tool holder 6. Then 5 mm deep grooves are cut with a 600 point angle (Fig. 2a) by rotating the shaft 1 and displacing the support 2 in the longitudinal direction of the shaft 1. These grooves are applied in two helical inserts in the same direction with a distance of 13 mm between the helices, while the distance between adjacent edges of the helical grooves is about 1.5 mm.

When the grooves have been cut, the end of the shaft 1, where the hard welding is to begin, is heated with the induction heating element 5 to 160 ° C along a zone approximately 250 mm long. Thereafter, the induction heating element is removed or pushed aside laterally and preparations are made for welding the first layer.

Using a consumable electrode in the form of a 2 mm thick round welding wire of high chromium steel with about 0.2% carbon and 1.3% chromium, which is industrially manufactured in the Soviet Union under the trade name CB-12x13. The coefficient of thermal expansion of this welding wire material is 10 x 10-6 1 / OC. More detailed data on this welding wire and the like are given in the description of embodiments of the invention which are represented in Table 2 later in the description. A flux containing 32% silica, 3% manganese oxide, 20% alumina, 45% 575 12 3% calcium oxide, 17% magnesium oxide, up to 1% iron oxide and 24% calcium fluoride was used as flux. This flux is manufactured industrially in the Soviet Union under the trade name AH-260.

The welding conditions have been chosen as follows: the welding speed is about 25 m / h, the arc voltage is 30 V and the welding current is 200 A.

The welding head 3 is moved to the starting point for the hard welding and the welding wire is positioned exactly in the center of one of the arranged grooves. The hard welding is then performed.

The metal of the consumable electrode is applied in two rounds along the helices (Fig. Zb) with the same distance as in the previous groove cutting and the ratio between the rotational speed of the shaft and the movement of the support 2 parallel to the longitudinal direction of the shaft 1 is the same as in the groove cutting. Under the given welding conditions, the grooves will be completely filled with the metal of the electrode in one and the same working operation.

After this, grooves similar to the first grooves, (Fig. 2a) but with opposite helix pitch (Fig. 2c) are cut, whereupon the consumable electrode metal is applied in these grooves on the same (Fig. 2b) 1 but also here with opposite helical direction under hard mode as in the first hard welding operation is the welding (Fig. 2d) corresponding to the grooves just cut.

In this case, the gaps between the two grooves of 1.5 mm were melted away and the metal of the shaft 1 was fused with the metal of the melting wire 4. In this way, the entire surface of the shaft 1 is covered with the metal of the consumable electrode and a first welding layer 8 is formed (Fig. 3).

Fig. 3 shows a cross section through the shaft 1 with the first layer 8 and this clearly shows the shape of a boundary layer S located therebetween. As can be seen from the drawing, the intermediate layer S has a relief structure consisting of depressions and projecting zones which alternate at least in the length 1 of the shaft 1 direction, ie in the same direction as the most risky forces acting during the work of the shaft.

Once the first layer has been applied, the following weld layers are then applied to the shaft until a required thickness of the coating has been obtained with a plus for mechanical machining.

The following weld layers are applied without any mechanical pretreatment, using the same welding wire and flux as for the first layer. The welding conditions are basically the same as with the application of the first layer, but the welding current is reduced by 20% and thus amounts to 160 A. g Each subsequent layer is normally applied in a single working operation along a helix with a relative distance between the metal strands in the layer of 0, 35.

When a layer of the desired thickness is welded to the shaft, the latter is cooled without stopping its rotation and a mechanical finishing of the overlay welding layer is performed until the desired dimensions are reached with 1 to 1.5 mm plus dimensions for final machining.

Then the hard-welded shaft is tempered 1. To do this, it is positioned in the vertical direction in a hearth shaft furnace. The shaft 1 provided with the hard welding layer.9 is then heat treated under the following conditions: heating: at 63o ° c at a rate of eo ° c per hour, maintaining this temperature for 4 hours and cooling together with the hearth shaft furnace.

Fig. 4 shows a diagram of the distribution of the remaining stresses over a cross section through the shaft 1 with a coating 9 applied according to the present invention. This diagram has been obtained with the well-known Zax method by drilling and turning off a test specimen. with continued voltage measurements according to which residual voltages were calculated.

As shown in Fig. 4, according to the above procedure, the shaft 1 provided with a welded layer 9 in the melting zone between the shaft 1 and the coating 9 has residual stresses which consist of compressive stresses of about 10 kgf / mm 2.

These compressive stresses near the layer 9 amount to about 25 kgf / mm 2.

Example 2 This example relates to the manufacture of a ship propeller shaft with a diameter of 400 mm and a cylindrical zone of 6,000 mm to be coated with cemented carbide. The shaft must have a corrosion-resistant coating over its entire length on the cylindrical zone and at the same time a_bearing metal layer in two zones where bearings are arranged. This shaft is made of perlite structural carbon steel with a carbon content of about 0.4%. This steel is manufactured industrially in the Soviet Union under the trade name Steel 40. This steel has a coefficient of thermal expansion of 14 x 10-6 l / ° C. In the manufacture of such a hard welded shaft, the same welding machine as described in Example 1 was used.

Before the first layer is applied, the cylindrical surface of the shaft is turned to a diameter for hard welding. 1 Then the preparations for welding the first layer take place. As the consumable electrode, a welding wire Cb-12x13 with a diameter of 2 mm 2 is used, i.e. the same as in Example 1.

Furthermore, the same flux AH-26c as in Example 1 was used as the flux. The welding conditions have been chosen as follows: the welding speed is 28 m / h, the arc voltage is 34 V and the welding current is 250 A. An induction heating element is then connected and one shaft end is heated to 250 ° C.

Then the first welding layer is applied. This operation was performed in a helical chord (Fig. 2a) so that welding strands 10 of the material of the consumable electrode have one and the same direction. A relative strand distance d for welding the first layer 8 is selected corresponding to the filling coefficient W of the projecting surface parts of the welding strand 1p. The coefficient W is defined as follows: _ __§â__ W _ BX h, (l) where Fd = actual cross-sectional area of the projecting part of the welding string 10, consisting of the metal of the consumable electrode, B = the width of the melting string 10 and h = the height of the welding string 10 projecting part (Fig. 5b) - 4 Under the said welding conditions of the first layer, the width B of the welding strands 10 becomes 14 mm and the filling coefficient W of their projecting surface parts = 0.55. It is well known to those skilled in the art that the relative string spacing a is the ratio of the center spacing m between the strings and their width B, ie _ m “- -§- (2). It follows that x B (3) becomes the center spacing m 'm = U. and taking into account that a = W, between the welding strands in the welding layer 7.7 mn. The center distance H in a simple helix is defined according to the following expression: H = HD m - (4) H D - m where D is = the diameter of the shaft.

Since the value m is considerably smaller than the shaft diameter D, in the case of helical welding in a single operation, the center distance H can be considered with sufficient practical accuracy to be equal to the center distance m between the melt strings, ie in this case H = 7.7 mm.

When the first layer has been applied, additional hard weld layers are gradually applied to the desired thickness achieved with a plus for mechanical processing. These layers are applied using the same welding wire and flux and under the same conditions as applied when applying the first hard weld layer. However, the relative strand distance α between the weld strands in the layer is equal to 0.35.

Thereafter, the mechanical processing of the hard-welded shaft and its heat treatment takes place. These operations are performed in the same manner as described in connection with Example 1.

Then bearings 11 (Fig. 6) are placed under the respective bearing seats. The bearings II are made of copper bearing alloy, for example an alloy containing 10% tin, 2% zinc and the rest copper. This alloy is industrially produced in the Soviet Union under the trade name ßpßq 10-2. After this, the bearings are machined to specified dimensions with the desired surface finish.

As shown in Fig. Sb, the intermediate layer S between the shaft 1 and the first layer 8 applied to the shaft has a relief structure with projections and depressions which alternately follow one another in the longitudinal direction of the shaft. The diagram with residual stresses in the shaft 1 with the overlay weld 9 and the bearings 11 thereon, manufactured according to the proposed method, has the same shape as the diagram described in connection with Example 1.

Example 3 This example relates to the manufacture of corrosion-resistant protective layers on a ship propeller shaft with a diameter of 300 mm and a length of l.200 mm. In order to save corrosion-resistant material, the bearing liner is made with welding overlay of this material which is applied to the base material of carbon steel in accordance with the present invention.

The bearing lining is made of perlite structural carbon steel sheet with a carbon content of about 0.35% which is manufactured industrially in the Soviet Union under the trade name Steel 35. This steel has a coefficient of thermal expansion of 14 x 10-61 / OC.

The thickness of the plate, from which the bearing lining is made, is equal to 16 mm. Sheet metal with the required dimensions is bent with bending rollers and its joint edges are welded longitudinally to form a hollow cylinder in this way.

Thereafter, the bearing liner is placed in a welding machine as shown in Fig. 1.

Then the bearing liner is clamped in the welding machine's dock, its inner diameter is turned out with 3 to 4 mm turning man left over the required dimension and its outside is turned off until the roller skin has been removed.

Then the preparations are made to apply the first hard weld layer under the same welding conditions as in Example 2. The consumable electrode and flux are also the same as in Example 2. The bearing liner is heated to 200 ° C. Then the first hard weld layer is applied but unlike Example 2 this operation is performed in three rounds along the helices in the same direction (Fig. 7). A relative center distance of the hard weld strands in the layer is selected by 0.55 i.e. the filling coefficient W of the projecting surface portions of the hard weld strands under specified conditions. With such a relative distance a, the distance HM for each applied helix becomes equal to H = W x (5) G xn MI where n is the number of working operations, ie 14 x 0.53 x 3 = 23.1 mm, and the displacement "a" in between becomes equal to: H a = -nl-. (e) d v s a - -ååšë-Ä = 7.7 mm.

After this first layer has been applied, the following layers are applied to the layer liner until the desired coating thickness has been reached plus the working time for mechanical processing. These layers are applied in the same way as the first layer along helices with the same direction in three rounds, but the relative distance G of the hard weld strands in the layers is chosen equal to 0.3.

The hard-welded bearing shell is then heat-treated. It is placed vertically in a hearth shaft oven under the following conditions: heating to 630 ° C at a rate of 100 ° C per hour, temperature treatment at this temperature for 3 hours and cooling together with the oven.

This is followed by mechanical processing of the inside of the hard-welded, ie carbide-coated bearing shells to the desired dimensions and an outer diameter base is applied at its ends.

The bearing shell is attached to a ship's propeller shaft in a known manner, for example shrinkage. The diameter of the bearing lining is then turned to the final dimension.

In the bearing liner made according to the described method, the intermediate layer S between the liner and the applied hard weld layer and the shape of the diagram of residual stresses are the same as for a shaft 1 with hard welded layer 9 according to Example 2. Example 4 This example relates to the manufacture of a shaft with a diameter of 70 mm and a length of 2,000 mm with a welded-on corrosion-resistant layer of 6 mm. The shaft to be coated with cemented carbide is made of perlite structural carbon steel with a carbon content of about 0.2%. This steel is manufactured industrially in This steel has a coefficient of thermal expansion of 14 x 10-6 l / OC.

In the manufacture of such a cemented carbide-coated or hard-welded shaft under the trade name Steel 20. welded shaft, the same welding machine and, in principle, co-welding conditions were used as in the previous examples. However, in view of the relatively small diameter of this shaft and its considerable length, the first metal layer has been welded in five cross-extending helices in the manner proposed according to the invention.

A 2 mm diameter welding wire with about 0.06% carbon and 1.4% chromium, which is industrially manufactured in the Soviet Union under the trade name Cb-06x14, was used as the consumable electrode.

The thermal expansion coefficient of this welding wire is 10 x 10-6 l / OC. A flux with the trade name AH-26c was used as flux.

After the shaft has been clamped in a welding machine, the following welding conditions are determined: the welding speed is 25.5 m / h, the welding voltage is 32 V and the welding current 220 A.

Under these conditions, the welding string of the metal of the consumable electrode has a width B of 14 mm and the filling coefficient w of the protruding part is equal to 0.6.

To reduce the thermal effect on the shaft when the first welding layer is applied, the number of work operations has been set equal to 8 for helices in both directions.

Based on the condition that the relative center distance d of the core welding strands in the same direction in the layer is equal to the filling coefficient W, it can be easily achieved that the distance HM for each helix in both directions is equal to: _ 2 Ux Dn x BWM 1112132 -4 (na M2 H (7) 10 15 20 25 30 35 453 577 19 where n is the number of helical work operations in the same direction.

Due to the large number of work operations, the distance for a helix, intended for several work operations, should be calculated using this equation. Calculations according to this show that the helical distance in the case in question shall be equal to 135.4 mm. After the shaft end has been heated to 200 ° C in the same way as in the previous example, helical lines are welded, for example, clockwise one by one with the helical distance HM equal to 135.4 mm. After the welding strand of the hard metal of the consumable electrode has been applied along this helix, a second helix is applied in the opposite direction, i.e. counterclockwise by welding (Fig. 8). This second helix is started opposite the starting point of the first helix, i.e. 1800 offset about the longitudinal axis of the shaft 1.

When the hard welding along the second helix is completed, the third helix is hard welded in the same direction as the first but offset relatively the same in the longitudinal direction of the shaft a distance H a = -f-'l, in the present case reaching "= 16.6 mm .

In the future, the following helical lines are hard-welded in a similar manner and in said order, whereby the first hard-welded layer is formed.

The boundary layer between the shaft 1 and the first applied hard weld layer has a relief structure with alternating successive depressions and projections both along the longitudinal direction of the shaft 1 and around this shaft. Such a relief surface is more pronounced in comparison with the boundary layer S obtained in accordance with the procedures described in Examples 2 and 3 (Fig. Eb).

When the first layer is applied, the following hard weld layer follows on the shaft, etc. until the required coating thickness has been reached with the working time for mechanical processing.

All subsequent welding layers are applied along helices with the same direction in eight working operations for each individual layer. In this way, the welding conditions are maintained in principle in the same way as for the welding of the first layer, and the welding wire used together with the flux is the same as before. However, the welding current is reduced by 20%, i.e. in the present case it becomes 180A.

This is followed by the mechanical machining and stress-annealing annealing of the hard-welded shaft in the same way as in the previously described examples. The shape of the diagram of residual stresses in the shaft manufactured according to this method is similar to that of the above-described embodiments with hard welding.

Example 5 This example shows a manufacturing method for hard welded shafts where the first welding layer is applied by spot welding with a metal consumable electrode in accordance with the invention.

This example relates to the manufacture of a shaft with a diameter of 100 mm and a length of 2,500 mm which is coated with a 6 mm thick corrosion-resistant layer. The shaft in question is made of steel 35.

For the application of the overlay welding layer, 2 mm welding wire was used which contains 0.12% carbon and 1.3% chromium and which is industrially manufactured in the Soviet Union under the trade designation Cb-12x13. The thermal expansion effect of this welding wire is 10 x 10-6 1 / OC. Flux AH-26c was used as flux.

In principle, the same welding machine was used for the application of the coating as in the previously described examples. However, in order to apply the spot welds of the first welding layer with a stable external characteristic regarding the power supply of the arc, stepwise feeding of the welding wire is applied. For this purpose, a drive roller 12 in the form of a specially designed roller provided with flattening 13 is used in the wire feed device (Fig. 9). Furthermore, there is a stopping device 14 which restricts the movement of a driven roller 15 which is pressed against the driving roller 12. In this way the feed of the welding wire 4 is stopped when the flat places 13 10 15 20 25 30 35 453 577 21 lie in the middle of the driven roller 15. These flattened points 13 have such dimensions that the ratio between the feed time of the welding wire and its rest time is in the order of 0.55 - 0.75.

The welding conditions for application of the first layer are as follows: the welding speed is 26 m / h, the welding voltage amounts to 30 - 32 V while the welding current is 200 - 220 A. To obtain a stable welding under said conditions, the feed speed of the welding wire to the shaft 1 is equal to 156 m / h.

Before the first layer is applied, at least the part of the shaft where the welding is to begin is heated over a distance of about 300 mm in length to about 300 ° C by means of an induction heating furnace in the same manner as described in previous examples.

Then the first welding layer is applied. For this purpose, the shaft is rotated and the support 2 is displaced with the welding head 3, whereby the helical weld on the shaft is produced in a similar manner as in the previously mentioned examples (Fig. 10). layer of 0.85. operation with a relative distance conventional According to experimental results, such a relative distance a under the said conditions gives an overlap of the melting zones of the spot welders in the adjacent turns of the helix.

During the feed of the welding wire 4 which takes place when the wire is in contact with the round surface parts of the drive roller 12, an electric arc is lit and a small click of the material of the consumable electrode is placed on the shaft. Under the said welding conditions, the welding wire feed time to the surface of the shaft is about 0.5 - 0.6 sec and the diameter of a spot-welded metal click from the consumable electrode is 15 - 16 mm. Upon further rotation of the drive roller 12, one of the flattening 13 ends up in the middle of the wire. Although the specially designed drive roller 12 continues its rotation, the feed of the melting wire then ceases.

When this takes place, a short burning period first arises, under the said conditions of 0.20 - 0.25 sec, caused by the span of the arc growing, and when this reaches its critical value, the arc goes out. When the specially designed drive roller 12 rotates further so that the round surface of the roller 12 comes back into contact with the melt wire, the feed of the melt wire is resumed. Since under said welding conditions for the first layer the arc burn timeout is less than 0.8 sec before the melting wire feed is resumed, the end of the melting trees is still in the middle of an area of molten and ionized slag formed during the application of the previous spot weld. Under these conditions, a stable arc ignition is obtained, and the welding process for the next spot weld with the consumable electrode metal is started again.

In the following, the melting process is repeated. The periods between the different working steps for applying spot welds with the consumable electrode amount to 1.4 sec. The center distance between successive spot welds on the shaft amounts to 10 mm, ie 0.63 - 0.66 of the diameter that these spot welds have on the shaft surface.

When the first layer is welded, a conventional welding wire feeding device is installed which provides a constant wire feeding speed to the surface to be coated.

The following weld layers are applied under the same welding conditions and at the same welding speed as when applying the following layers in Example 4.

When the required number of weld layers has been applied, the hard-welded shaft and strain relief annealing gas are processed in the same manner as described in the previous example.

The intermediate layer S between the shaft 1 and the first layer 9 in the welded coating 9 represents a strongly pronounced relief surface with a honeycomb structure. The diagram of residual stress in the case of the proposed method according to the invention has hard-welded shafts similar in shape to the diagram of hard-welded shafts manufactured in accordance with Examples 1-4.

Example 5 shows one of the possibilities for spot welding application using a profiled drive roller in a welding wire feeding device. Since the spot welding methods are not directly related to the present invention, no further examples are described here. However, it is clear to those skilled in the art that spot welding can be applied in other ways and by other means, for example by using a cam drive roller whose surface provides different feed speeds for the welding wire within an area. for stable arcs or by using electric stepper motors or periodically variable speed drives for the welding wire supply device, or by using an arc welding energy source with periodically varying characteristics, or by combined use of said possibilities. The welding conditions for the first layer and the ratio between the arc burn time and the time when it is extinguished are in principle the same as mentioned in Example 5 and give an application of the first layer with a center distance between the overlay spot welds of 0.30 - 0.68 of the diameter of these spot welds. on the shoulder surface.

Embodiments of the present invention described in Examples 1-5 relate to the manufacture of hard-welded shafts, the applied layer consisting of one and the same metal. The following examples relate to the manufacture of shafts with coatings constructed of different metals.

Example 6 This example relates to the manufacture of a hard-welded shaft with a coating whose outer layers are made of austenitic stainless steel.

The shaft to be hard welded is the same as in Example 4. As mentioned above in Example 4, the shaft is applied to the first layer of chrome steel in the form of intersecting helices.

After the first layer has been applied and the shaft has cooled, it is surface-treated in a third way.

Preparations are then made for the application of austenitic stainless steel. A consumable electrode is used in the form of a 2 mm diameter fusing wire containing about 0.04% carbon, 1.9% chromium, 1.1% nickel, 3% manganese and manufactured industrially in the Soviet Union under the trade name Cb- 04Xl9HllM3. The electrode material has a heat dissipation coefficient of 16 x 10 '61 / ° c.

The welding conditions for the first and subsequent layers 10 l5 20 25 30 35 453 577 24 are selected as follows: the welding speed is 25 m / h, the welding voltage is 32 V and the welding current is 40 A. All layers with austenitic stainless steel are welded together with screw lines with the same direction in eight steps, as described in Example 4 and with constant arc welding characteristics.

When all layers have been applied, mechanical finishing and stress-annealing annealing are carried out in the same way as in Example 5.

The shaft 1 manufactured in accordance with this method has a coating in which the outer layers 16 (Fig. 11) are made of austenitic stainless steel and between the layer 16 and the shaft 1 there is an intermediate layer 8 of chrome steel.

To convert residual tensile stresses developed in the austenitic steel layers into compressive forces, the hard welded surface can be rolled. In this case, the distribution diagram for residual stresses may be similar to that of shafts manufactured according to examples 1-5.

Example 7 This example relates to the manufacture of a hard-welded steel shaft whose total outer layer 12 mm thick is made of bronze to give its bearing zones corrosion and abrasion resistance.

The shaft to be hard welded is made of steel 35, has a diameter of 300 mm and a length of 51,500 mm.

This shaft is coated with a welded chrome steel layer with protrusions from the base of this layer to the shaft metal in accordance with the present invention. Such coating can be performed according to all the procedures described above in Examples 1-5, especially by applying the metal from a consumable electrode in helical form in a single working operation as described in Example 2.

After the application of the first layer, the shaft is cooled and the layer is finished by a third type of surface treatment.

Preparations are then made to apply bronze.

A consumable electrode is used in the form of a 2 mm thick fuse of silicon bronze which is manufactured industrially in the Soviet Union under the trade name K M q 3-l. This bronze contains 2.75 - 3.5% silicon, 1.0 - 1.5% manganese and the rest 10 15 20 25 30 35 453 577 25 copper. The welding speed amounts to 18 m / h. The bronze is applied by argon impulse welding under the following conditions.

The auxiliary current is 90 A, the auxiliary arc voltage is 22 V, the pulse current is sso A, the current pulse time is 1.8 msec, the pulse frequency '50 Hertz.

All bronze layers are applied along helices in a working operation with a relative distance between the metal welding strands in each layer equal to 0.55.

After a bronze layer with the required thickness plus manpower for mechanical processing has been applied, the hard-welded shaft is further processed and stress-annealed. The stress annealing takes place with the shaft vertically in a hearth shaft furnace under the following thermal conditions: heating to 630 ° C at a rate of 100 ° C per hour, heat treatment at this temperature for 3.5 hours, cooling together with the furnace.

After this, the shaft is finally treated to the desired surface quality.

The distribution diagram of residual stresses for the hard-welded shaft manufactured in accordance with the above procedure takes the same form as for a hard-welded shaft with a coating of austenitic stainless steel that has not been rolled.

Hard-welded parts made in accordance with the present invention as described in the illustrative examples have a relief shape on the intermediate layer S in the melting zone between the metal 1 of the part and the first layer 8 applied thereto while remaining compressive forces are present in the melting zone and in the first overlay welding layer 8 In the melting zone, a smooth transition between different coefficients of thermal expansion and the absence of abruptly varying stresses is ensured. Macro- and micro-defects in the melting zone of such a part are as a result in a compression stage and should not be subjected to any major tensile forces during use or, if the remaining compressive stresses are sufficiently large, such tensile forces will does not develop at all. Under these conditions, the occurrence of microcracks in the melting zone and their growth are extremely unlikely. At the same time, the relief structure of the intermediate layer S and the absence of voltage jumps in the melting zone significantly reduce the probability of coating shear.

According to the fatigue resistance and corrosion resistance of the present invention hard welded parts have been determined on specimens made with combinations of the material of the part and overlay welds, including plain bearing elements, shown below, the diameter of the samples being 60-70 mm. These tests were performed in the form of an installation that included a pure alternating load of the sample with a frequency of 1,000 - 1,750 bel / min. In the study of long-term corrosion resistance, seawater in the form of a 3% solution of sodium chloride was used as the aggressive environment. The basis for the fatigue tests was equal to 10 x 106 cycles and the long-term corrosion resistance was determined on the basis of so - so x 106 The tests have shown that the fatigue strength of the samples cycles. is in the range 20 - 24 kgf / mmz and that the long-term corrosion resistance on the basis of 10 x 106 cycles is in the range 18 - 21 kgf / m2. Fatigue tests of samples according to the invention with welded coating and bronze layers have shown that the bronze layers do not lower the fatigue strength of the samples. The latter were also not reduced by defects that arose during the welding process, such as gas or slag inclusions and surface cracks in the samples that arise during the test.

The production and testing of the samples were carried out in accordance with the procedure that made it possible to extend the examination results to special units as well.

All these factors made it possible to document the possibility of extensive use of the present invention, while achieving all the above-mentioned advantages, for the manufacture of large metal parts which are exposed to considerable dynamic loads and which operate in an aggressive environment. The invention makes it possible to achieve a long service life for such parts and at the same time to reduce their manufacturing costs by saving on rare and expensive materials.

One of the direct uses of the present invention are ship propeller shafts of large length in the order of a few meters and with a large ratio between shaft length and shaft diameter and whose tasks are associated with the transmission of large forces and which are exposed to aggressive seawater. 453 577 Chemical compositions of perlite structural 28 Table 1 u. Kcl steels Trade name C Mn Si Ni Steel - 20 0, 17 ~ 0.24 0, 35 ~ 0.65 0, 17 ~ 0, 37 - - - 30 0.27 ~ 0.35 0.50 ~ 0.80 0, l7 ~ 0.37 - - - 35 0.32 ~ 0.40 0.50 ~ 0.80 0, l7 ~ 0.37 - 40 0.37 ~ 0 , 45 0, S0 ~ 0.80 0, l7 ~ 0.37 - - 40 XH 0.36 ~ 0.44 0.50 ~ 0.80 0, l7 ~ 0.37 0.45 ~ 0.75 l, 0 ~ å, 4 453 577 29 m ~ oo w ~ ° .o | mzw N fi zc fi owïw fi Nz fl w ° .o Hw> m nu wo.o Hw> w mm m: H fl mmHx «om ~ oo @ ~ °. ° @. ° zm.o ~: ~ H fl zm omzw fl ~» A mo = mo mo. o uw> @ hm emzo fi mm fl xwo ° mo.o mH °. ° ° .Hzm. ° 4 o fi zw owzw fl ~ 2H o_Hz «.o wo.o uw> æ nu emmm fi xmo m ~ oo wH °. ° | 1 o fi zw øwzw fi ~: H Q. ~ zm.o wo.o uw> m fi w mmm fl xvq ° mo.om ~ ° .o I 1 o @ .o uw> m fi w m fi zm fl ~ _ ° zm.o> .oz ~. o wo.o »w> m fi w« Hxw ° = m ° .om ~ ° .c 1 | ow.o Hw> w mm «H2 ~ H ~ .o1m.o> .øzm.o ~ H.o> æo.o m fi xo fl = mo.o m ~ o.o | | ow.Q nw> æ fi w q fi zwa> _ @ zm.o ~ .ozm.o «H.o2mQ.o mHx ~ A nu uw> m um> w fi w mm mw fi a oz Hz nu az fi m u camcm fl wunmm umømuumum> m> m mc fl cnummcmeëmm xm flfi mx N H fl wnma

Claims (15)

10 15 20 25 30 453 577 30 PATENT REQUIREMENTS 1. 1. Hard-welded part (1), to which several welding layers (8,9, 16) have been applied by means of arc welding with a consumable electrode, mechanical processing and temperature treatment, characterized in that a boundary layer (S) between the part (1) ) and the first coating layer (8) in a melting zone has a relief shape with depressions and projections which regularly follow one another in the same direction as the most hazardous forces are estimated to act in the part (1) in question during its use, and that from the manufacturing process remaining internal stresses in the form of compression forces at least within the thickness range of the melting zone are distributed in the same direction. Hard-welded part according to Claim 1, characterized in that the hard-welded coating (9) consists of different layers (8, 16) of different metal and that the boundary layers in their melting zones have a relief structure. Hard-welded part according to Claim 1 or 2, characterized in - made of low-alloy steel or carbon steel, with a corrosion-resistant coating, characterized in that at least the first layer (8) of the coating is directly fused to surface of the part (1) and consists of chrome steel. Hard-welded part according to Claim 2 or 3, characterized in that the first layer (8) consists of chrome steel and is coated with a further layer (16) of austenitic stainless steel. Manufacturing method for hard-welded parts according to any one or more of claims 1-4, comprising applying bag welds in several layers to a part (1) with a relief-shaped boundary layer (S) by means of arc welding with a consumable electrode (4). ), mechanical processing and temperature treatment thereof, characterized in that a first layer (8) is applied so that it forms regular, continuously successive, in at least 10 15 20 25 30 35 453 577 31 originating from the base of this layer (8) at the boundary layer (S) and into the metal of the part (1), and that the consumable electrode (4) used for applying this layer consists of a metal whose coefficient of thermal expansion is lower than the for the metal of the part (1). _ Manufacturing method according to claim 5, characterized in that the projections from the base of the first layer (8) into the metal of the part (1) are effected by mechanical treatment thereof and by subsequent welding of metal in depressions formed below the course of the mechanical processing. Manufacturing method according to claim 5, characterized in that the projections from the base of the first layer (8) and into the metal of the part (1) are effected by welding this first layer (8) with a consumable wire electrode with the metal welding strands in a and the same direction and with a ratio (u) between the strand center distance (m) and the strand width (B) in the welding layer which is equal to the filling coefficient (W) of the weld strands projecting outside the part (1). A manufacturing method according to claim 5, characterized in that the projections from the base of the first layer (B) into the metal of the part (1) are achieved by welds this first layer (8) with a wire electrode with cross application of the welding strands and with a ratio (a) between the strand center distance (m) and strand width (B) for welding strands with one and the same direction in the layer, which ratio (a) corresponds to the fill coefficient (W) for the parts of the strings projecting outside the part. Manufacturing method according to claim 5, characterized in that the projections from the base of the first layer (B) and into the metal of the part (1) are achieved by spot welding this layer with a center distance between adjacent overlay spot welds of 0, 30- 0.68 of these spot welds diameter. Manufacturing method according to claim 9, characterized in that the spot welding of the first weld metal layer (8) takes place by advancing a consumable wire electrode against the surface of the part (1) at a periodically varying speed at constant relative speed of movement between the part (1) and the electrode along the surface of the part (1) and with stable energy supply characteristics. 11. ll. Manufacturing method according to claim 10, characterized in that the periodic variations of the feed electrode feed rate are obtained by stepwise electrode feed. Manufacturing method according to claim 9, characterized in that the spot welding of the first metal layer (8) is carried out under conditions with periodically varying energy supply characteristics with continuous feeding of the consumable wire electrode to the surface of the part (1) and with constant relative speed of movement along its surface. . Manufacturing method according to one or more of Claims S-12, characterized in that the first metal welding layer (8) is applied with a wire electrode in a few working operations. Manufacturing method according to one or more of Claims 5 to 12, characterized in that the weld metal layer following the first layer (8) is applied under conditions which give the least possible thermal effect on the melting zone between the metal (1) and the metal. first layer applied thereto (8). Use of a hard-welded part, preferably as a ship propeller shaft, to which several welding layers (8, 9, 16) have been applied by means of arc welding with a consumable electrode, mechanical processing and temperature treatment, wherein an boundary layer (S) between the part (1) ) and the first coating layer (1) in a melting zone has a relief shape with depressions and projections which regularly follow one another in the same direction as the most hazardous forces are calculated to act in the part (1) in question during its use, and to remain 453 from the manufacturing process. 577 33 internal stresses in the form of compression forces at least within the thickness range of the melting zone are distributed in the same direction according to claims 1-4 with bearing elements characterized in that the bearing element (11) is arranged on it on the part (1) welded the multilayer coating (9) and / or that the bearing support element (1) is made of coatings, including bearing metal alloy, and fused to it on the coating (1) arranged the coating.