KR102219744B1 - Anti-galling method for treating materials - Google Patents

Abstract

A method of inhibiting galling for treating a material, comprising: a first preliminary heat treatment step for increasing surface hardness and a second for at least one of at least two elements connected to each other with at least one degree of freedom and made of a metallic material. Performing a preliminary surface grinding step, the method comprises performing a first step of cleaning at least one portion of the surface of at least one element previously subjected to the preliminary step, and at least one of the surface of the at least one element previously washed Performing a second step of performing a shot peening treatment on a portion of, and performing a third step of forming a molybdenum disulfide layer on at least one portion of at least one element previously subjected to the shot peening treatment. Done.

Description

Anti-golling methods for processing materials {ANTI-GALLING METHOD FOR TREATING MATERIALS}

The present invention relates to a method for inhibiting gouling for treating materials.

During normal operation, two mechanical bodies that slide with respect to each other can undergo a phenomenon called galling.

"Goling" refers to the occurrence of locking of two or more complementary moving mechanical members, usually due to excessive sliding friction, which may temporarily or permanently interrupt the regular operation of the mechanical members due to excessive sliding friction. have.

The golling can occur for a variety of reasons, which can lead to one consequence, ie, excessive overheating of the pushing unit. For example, golling can result from lack of lubrication, excessive stress at full power and extended overtime (e.g. caused by operating speeds higher than the machine's actual capability), or incorrect play between parts. (Too little play between the bushing and each pivot can, for example, lead to an interruption of the lubricating film, and excessive play makes accurate isolation of the lubricating oil impossible and can also lead to collisions between the elements).

Many mechanical couplings are provided in which no lubricant is used, but there is usually a lubricant between the connected elements in reciprocating motion.

In principle, the present invention relates to a pivot-bushing assembly comprising an element which is preferably made of a metallic material (eg steel, aluminum and other types of alloys) and is reciprocally rotated.

In this kind of assembly, golling often occurs which causes machine downtime and noticeable damage to the pivot.

To avoid these drawbacks, lubricant is often interposed between the pivot and the bushing (within the clearance between them) and is isolated there by a specific sealing element.

However, in some cases, the lubricating oil may not be sufficient to avoid goling, especially after a large amount of operating time.

Therefore, goling occurs in particular in the assembly of the known kind. In order to avoid the occurrence of this golling, periodic maintenance is provided to check the condition of the lubricant in the clearance between the pivot and the bushing and restore the ideal condition of the lubricant.

Therefore, a known type of assembly is subject to a golling phenomenon, and frequent and expensive periodic maintenance of the assembly is required if this phenomenon is to be avoided (causing machine downtime).

In order to reduce the occurrence of gouling, it is known to perform a different kind of heat treatment on a pivot made of quenched and tempered steel, after which the surface of the pivot is ground.

Even after the above treatment on the pivot, the pivot may in any case cause a golling phenomenon, so that a long service life of the pivot is not guaranteed.

It is an object of the present invention to solve the above-described problem by proposing a method for suppressing gouling for processing materials that can minimize the occurrence of gouling to a negligible degree.

One object of the present invention, within the scope of this goal, is to propose a method for suppressing goling for processing materials, which can minimize the risk of goling of a pivot rotating with respect to a mating bushing.

Another object of the present invention is to propose a method for suppressing golling for processing materials, which can reduce periodic maintenance of mechanical couplings comprising elements to which the method is applied.

Another object of the present invention is to propose a method for inhibiting golling for treating materials, which is inexpensive, relatively simple to provide in practice, and safe in application.

The above objectives and these and other objectives, which will become more apparent below, are achieved by a method of inhibiting galling for processing a material, in which at least two elements are connected to each other with at least one degree of freedom and are made of a metallic material. For at least one of, a first preliminary heat treatment step and a second preliminary surface grinding step for increasing the surface hardness are performed, the method comprising:

-Performing a first step of cleaning at least one portion of the surface of the at least one element previously subjected to the preliminary step,

-Performing a second step of performing a shot peening treatment on the at least one portion of the surface of the at least one element previously washed, and

-It consists of performing a third step of forming a molybdenum disulfide layer on the at least one portion of the at least one element previously subjected to the shot peening treatment.

Other features and advantages of the present invention will be more clearly seen from a preferred but non-exclusive embodiment of a method for inhibiting goling for treating a material according to the present invention, which is shown as a non-limiting example in the accompanying drawings, and FIG. It is a front cross-sectional view taken along a transverse plane of one possible rotatable mechanical coupling provided by applying the method for preventing goling according to the present invention.

Referring particularly to the drawings, the reference numeral "1" as a whole denotes one possible rotational mechanical coupling provided by applying the anti-golling method for processing the material according to the invention.

The method according to the invention can be applied to mechanical couplings with at least one degree of freedom.

The element is preferably made of a metallic material, for example a metal alloy such as steel, or a metal in a substantially pure state (eg aluminum) may be mentioned. When referring to elements made of steel, quenched and tempered steel will generally be used.

In the anti-goling method according to the present invention, at least one of the at least two elements is subjected to a first preliminary heat treatment step and a second preliminary surface grinding step for increasing the surface hardness.

The two preliminary steps are usually those applied in the background art.

The method according to the invention carries out additional successive steps for at least one element.

In fact, it is necessary to carry out a first step of cleaning at least one part of the surface of the at least one element previously subjected to the preliminary step.

Then, it is necessary to perform a second step of performing a shot peening treatment on the at least one portion of the surface of the at least one element previously washed.

Finally, it is necessary to perform a third step of forming a molybdenum disulfide layer on the at least one portion of the at least one element previously subjected to the shot peening treatment.

It is useful that the cleaning step also comprises surface degreasing at least one portion of the surface of the at least one element previously subjected to the preliminary step.

Degreasing consists of removing oil or dirt from the surface of the element (usually made of steel) before the next treatment (mechanical treatment, thermal treatment, etc.) or surface finishing. It is important to remove grease and dirt because the presence of organic molecules (essentially composed of carbon) can be dangerous.If heat treatment is performed, carbon can actually enter the matrix of the material during the heat treatment (which generates heat). Even with some mechanical treatment, the carbon contained in the oil present on the outer surface of the part to be processed may move), thereby causing aesthetic damage to the part and also local deterioration of its properties. Carbon enrichment can negatively affect the mechanical properties of the part as hardening and embrittlement, and even lower the corrosion resistance of the part.

Degreasing can be carried out with an organic solvent using the chemical principle of "melting with each other" or can be carried out with an alkali solvent or an acid solvent in an aqueous base. In this second case, it acts on the hydrophilic portion of the compound;

The second step of performing a shot peening treatment on the at least one portion of the surface of the previously washed at least one element continues until a residual compressed state of 200 MPa to 10000 MPa is obtained in the at least one portion, The ideal value of residual compression that can be obtained for the correct implementation of the method according to the invention is approximately 1100 MPa.

Shot peening consists of surface cold hammering using vigorous jets of spherical shots or cylindrical shots (called wire cut shots) obtained by cutting wires.

Machines that perform this treatment, i.e. peening machines, use one or more fast-rotating impellers, usually centrifugal impellers, or compressed air to direct jets of rounded or cylindrical shots towards the part to be machined, and in any case, grit ( The materials used for grit) are cast iron, steel, glass and more rarely ceramic.

Moreover, shot peening improves the distribution of surface tension disturbed by mechanical treatment and/or heat treatment and also weakens the concentration of labor caused by notches, threads, decarburization, and the like.

In terms of implementation, shot peening is similar to sanding, since it acts more on plastic than abrasion, but more like rolling for its intended purpose.

In fact, shot peening causes surface compression, because its jet causes plastic deformation that propagates to depths of tens of tenths of a millimeter in the material under consideration, and technically improves the distribution of surface tension to increase the fatigue strength of the treated part. Because it plays a role.

This effect arises due to residual compressive tension induced on the surface of the material and in the underlying layer, which can reduce the internal tension when the part is stressed. Therefore, the material becomes more resistant to fatigue stress.

At the end of the treatment, as a secondary effect, because of the microcavities generated and superimposed on each other, the amount of light reflected from the material is also reduced (i.e., a kind of glossy finish).

If the properties of the material being shot peening are constant, the effect of shot peening will depend on the hardness and size of the shot, flow rate, stream velocity and impact angle, distance between part and projection system, strength, and coverage. The shot peening intensity, measured in Almen degree, is the two sides of a layered specimen (76 x 19 mm) obtained from C 70 UNI 7845 killed steel hardened and tempered at 44 ÷ 45 HRC in the direction of incidence of the stream. It is evaluated as a curvature performed as one, and its thickness "s" can take three different values corresponding to short peening of weak intensity N, medium intensity A and strong intensity C. The curvature resulting from the stream of shots is measured with a quadrant comparator.

Coverage is determined by applying a stream of shots to the polished specimen for a time corresponding to the intensity involved and measuring the area of all impacted areas within a circumference of a normally set diameter at a magnification of 50 times, and the coverage is the impacted area. It is defined as the ratio between the sum of the areas of and the original area.

The second step of performing a shot peening treatment on the at least one portion of the surface of the at least one element washed previously is performed with S110 steel balls having a diameter of 0.01 mm to 1.5 mm, preferably, about 0.3 mm ( In the method according to the invention, a ball having a diameter of the value observed for optimal treatment results) is used.

The second step of performing a shot peening treatment on the at least one portion of the surface of the previously washed at least one element is an intensity having a value of 4 to 20 almendo for the type A specimen (i.e., identified by the letter A. Medium intensity pinning).

Even in this case, it is appropriate that the ideal value of the pinning intensity, which refers to the pinning of the middle intensity indicated by the almendo and identified by the letter A, is approximately 6 or 8.

In either case, optimal results are obtained with 100% of the at least one portion, but the second step of shot peening is performed by providing a coverage of more than 60%.

By the third step of the method according to the invention, in which a layer of molybdenum disulfide is formed in said at least one part of at least one element, a layer with a thickness of 1 to 50 μm is provided.

Even in this case, it is convenient that the ideal thickness of molybdenum disulfide is 5 to 15 μm within the scope of the method according to the invention.

In the third step of forming a molybdenum disulfide layer on the at least one portion of at least one element, an aerosol containing more than 10% by weight of molybdenum disulfide, an inorganic resin, a solvent, and a propellant is sprayed on the at least one portion. It becomes.

It is preferred to use an aerosol with a content of molybdenum disulfide higher than 20% to obtain better results and also to obtain a more efficient and stable layer in the treated part of the urea.

The combination of steps indicated and provided by the method according to the invention is particularly effective, since the surface cleaning defines ideal conditions for the adhesion of a layer of molybdenum disulfide.

At the same time, shot peening creates a plurality of continuous microcavities in the outer surface of the element.

Due to this surface unevenness, adhesion of molybdenum disulfide is facilitated, resulting in locally produced higher thickness deposits that increase structural strength.

In addition, with respect to the same smooth surface, the surface affected by a plurality of consecutive cavities without discontinuities has a larger area, so the contact area between the molybdenum disulfide and the surface itself increases, and the toughness of the adhesion of molybdenum disulfide Silver is directly proportional to the area of the coated surface, so irregular surfaces achieve a higher stability stratification.

Finally, the residual tension created by the shot peening step ensures that the surface of the element is more rigid.

Since deformation can cause layer separation, elements that have undergone less deformation are more suitable for subsequent deposition of a layer of rigid material.

Therefore, the combination of the above steps entails a synergistic combination of overlapping the effects shown and ensuring the effectiveness of the mechanical coupling, which is surprising in terms of strength and durability and mechanical performance of the molybdenum disulfide layer.

The method according to the invention comprises an auxiliary step of removing material from the other of the two elements in order to increase the play between the two elements which are connected to each other.

In this case, the removal of material takes place, among the other elements, in at least one region that does not face and is not close to the at least one portion that undergoes the first to third steps.

By the removal of the material, the sliding between the two (or more) elements occurs only in the part to which the invention is applied, and in fact the other part is separated by a significant gap, which is the gap of the material provided in the aforementioned auxiliary steps. It is obtained by further removal.

Moreover, due to the increase in play, a larger amount of lubricant (oil or grease) may be contained within this play. The lubrication oil is isolated by each sealing element of the usual kind within the free space (gap) that exists between the elements, and a specific explanation for this would not be necessary (because it is known).

1 is a front cross-sectional view taken along a transverse plane of one possible rotatable mechanical coupling provided by applying the method for preventing goling according to the present invention.

According to a specific application according to the invention, which makes it possible to simply and immediately identify the many advantages and considerable possibilities of the invention, the first element consists of a pivot 2 and the second element consists of a bushing 3.

In the use state, the pivot 2 is rotatably inserted inside the bushing 3 and has at least one part 4 that slides in a corresponding area of the inner surface of the bushing 3, which part is from first to third. You will go through the steps.

The bushing 3 is material-removed from a part of its inner surface to form a larger diameter cavity area 5.

In this way, a clearance 6 can be formed between the pivot 2 and the region 5 of the bushing 3 (which may have a large dimension).

Within the clearance 6, a predetermined amount of lubricating oil that facilitates the relative rotation of the pivot 2 and the bushing 3 may be isolated.

The accompanying drawings in particular relate to one possible coupling of links of chains that are connected to each other.

A particular analysis of the configuration scheme given as an example, in this case, the links 7 and 8 of the chain are keyed to the bushing 3 with a predetermined interference.

Likewise, two other links 9, 10 (opposite those integral with the bushing 3) are keyed to the pivot 2 with a certain amount of interference.

In fact, according to the configuration defined above, the assembly of the pivot 2 and the links 9, 10 constitutes a first joint, and the assembly of the bushing 3 and the links 7, 8 constitutes a second joint. .

The two joints constitute a mechanical coupling, which is particularly effective when the method according to the invention is applied to the part 4 of the pivot 2 sliding on the inner surface of the bushing 3.

Finally, in order to isolate the lubricating oil in the clearance 6 formed between the pivot 2 and the larger diameter area of the cavity in the bushing 3, the sealing element () between the pivot 2 and the bushing 3 11, 12) are used.

Chains of the kind shown in the accompanying drawings are universally used in dirt moving machines and many other industrial processes.

The method according to the invention can, in any case, be applied to a significant number of other mechanical couplings and joints that are usually subjected to gouling because of the speed and frequency of the mechanical tension applied and/or relative motion.

Advantageously, the present invention solves the above-described problem by proposing a method for suppressing goling for processing the material, which can minimize the occurrence of gouling to a negligible degree.

This result is obtained by the synergistic effect of the shot peening step and the residual compressed state due to the presence of the molybdenum disulfide layer.

Advantageously, by means of the anti-goling method according to the invention, the risk of goling of the pivot 2 rotating relative to the mating bushing 3 is minimized and thus is particularly effective in the case of a rotational coupling.

Efficiently, the method for inhibiting golling according to the present invention can reduce periodic maintenance of a mechanical coupling including an element to which the method is applied.

In fact, due to the reduction in the occurrence of golling events and the presence of a larger (compared to the traditional kind of coupling) clearance 6, the number of maintenance interventions required can be significantly reduced.

Advantageously, the method for inhibiting goling according to the present invention can be carried out at a substantially low cost, is relatively simple to provide in practice and is also safe in application.

The invention thus created is subject to many modifications and variations, all of which are also within the scope of the appended claims, and all details may be replaced by other technically equivalent elements.

In the examples of the embodiments shown, individual features given in connection with a particular example may actually be interchanged with other features present in other examples of the embodiments.

In practice, the materials and dimensions used can be any depending on requirements and technical conditions.

Where a reference sign follows a technical element mentioned in the claims, that reference sign is included solely for the purpose of aiding the understanding of the claims and such reference sign is, for example, an interpretation of each element to which such reference sign is attached. Has no limiting effect on

Claims (10)

A method of inhibiting galling for treating a material, comprising: a first preliminary heat treatment step for increasing surface hardness and a second for at least one of at least two elements connected to each other with at least one degree of freedom and made of a metallic material. Conducting a preliminary surface grinding step, the method,
-Performing a first step of cleaning at least one portion of the surface of the at least one element previously subjected to the preliminary step,
-Performing a second step of performing a shot peening treatment on the at least one portion of the surface of the at least one element previously washed, and
-A method for inhibiting goling for processing a material, comprising performing a third step of forming a molybdenum disulfide layer on the at least one portion of at least one element previously subjected to the shot peening treatment. The method of claim 1,
The first cleaning step further comprises surface degreasing at least one portion of the surface of the at least one element previously subjected to the preliminary step. The method of claim 1,
The second step of performing a shot peening treatment on the at least one portion of the surface of the previously washed at least one element is continued until a residual compressed state of 200 MPa to 10000 MPa is obtained in the at least one portion, A method of inhibiting golling for processing materials. The method of claim 1,
The second step of performing a shot peening treatment on the at least one portion of the surface of the previously washed at least one element is performed with an S110 steel ball having a diameter of 0.01 mm to 1.5 mm, a method for inhibiting goling for processing materials . The method of claim 1,
The second step of performing a shot peening treatment on the at least one portion of the surface of the at least one element previously washed is performed with an intensity having a value of 4 to 20 Almen degrees for the A-type specimen Goling inhibition method for treating. The method of claim 1,
The second step of performing a shot peening treatment on the at least one portion of the surface of the at least one element previously washed is performed with a coverage of more than 60% of the at least one portion, for processing the material. How to suppress goling. The method of claim 1,
By the third step of forming a layer of molybdenum disulfide in the at least one portion of at least one element, a layer having a thickness of 1 to 50 μm is formed. The method of claim 1,
In the third step of forming a molybdenum disulfide layer on the at least one portion of the at least one element previously subjected to the sorption treatment, an aerosol containing more than 10% by weight of molybdenum disulfide, an inorganic resin, a solvent, and a propellant is the Sprinkling on at least one part, a method for inhibiting goling for treating materials. The method of claim 1,
And an auxiliary step of removing material from the other of the two elements to increase the play between the two elements connected to each other, wherein the removal of the material is performed by the first to third steps, among the other elements. A method of inhibiting golling for treating a material, taking place in at least one region that is not opposite and is not close to the at least one portion. The method of claim 1,
The first element is the pivot (2) and the second element is the bushing (3), and in the use state the pivot (2) is rotatably inserted into the bushing (3), and the inner surface of the bushing (3) A method of inhibiting goling for processing a material, having at least one part (4) sliding in a corresponding area and going through first to third steps.

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