RU2337802C2 - Shaft recostruction method - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: mechanical processing of the necks of the shaft with a depression in the body of the shaft is carried out on the whole width of the reconstructed surface. A preloaded thin walled cover plate compensating for metal wearing is installed in form of sectional or half ring. The thin walled cover plate used has width b, length L and thickness δ_"л", which are determined from a given expression. After installing the cover plate on the neck of the shaft with preloading, the cover plate is uniformly compressed along its whole surface. The cover plate is fixed to the processed necks by welding their contact points and boiling them with the neck of the shaft. Butt-welded joint are then obtained. The cover plate, made in form of a sectional ring, before welding it to the contact points, is heated to temperature t°, while the contact points for the half ring cover plate are welded with obtaining of the first butt weld, after which the cover plate is heated to temperature t° and the contact points of the half ring are welded with obtaining of a second butt weld. After that, the butt welds are cooled to ambient temperature. Electric rivets are put onto the surface of cover plates on both sides of the butt weld. The necks are ground to the nominal or repair size.

EFFECT: provision for well defined allowance between the cover plate and neck of the shaft.

3 dwg, 1 ex

Description

The invention relates to mechanical engineering and can be used to restore worn shaft necks and the manufacture of shafts.

A known method of restoring worn parts, mainly the necks of the crankshafts, in which a split sleeve is applied to the worn surface and the joints are welded. On the split sleeve, through holes are made, which are welded with wear-resistant antifriction porous material, and the joints of the split sleeve are made with a broken surface (AS No. 1368151 B23P 6/00).

The disadvantage of this method is:

1. The inability to create a given interference sleeve split relative to the shaft journal.

2. The split sleeve is installed on the shaft neck in a wet state, which requires its subsequent hardening, and, consequently, a decrease in the fatigue strength of the entire shaft.

3. The welding of a raw split sleeve complicates the technology of shaft restoration with its low quality.

A known method of manufacturing a crankshaft, including the manufacture of the main and connecting rod necks with fillets, the execution on the necks symmetrically with the fillets of annular recesses with smooth conjugation with the surfaces of the necks by means of fillet transitions. An annular element of material with predetermined tribochemical properties is installed in annular recesses along their entire length with subsequent fixation, the outer cylindrical surface of which is located not lower than the edges of the transition from the fillets of the corresponding necks to the recess. The length L in the recesses, the radius R of the fillets of the neck and the length L of the neck are performed based on the following size ratio of the specified parameters:

L-2R≤1≤L-R, and the radius r of the fillet transitions of the recesses is equal to 0.5 R. Segment inserts are installed in the annular recesses with subsequent fixation. In the annular recesses, a tape rolled into a ring is installed with subsequent fixation (a.s. No. 1796781, F16C 3/06, 9/04).

The disadvantages of this method are:

1. The inability to create a strictly defined interference between the tape and the neck of the shaft.

2. Ring grooves create a local concentration of internal stresses and reduce the fatigue strength of the shaft.

A known method of restoring the necks of the shafts, including machining the necks, installing composite repair shells, welding the joints of the shells in a compressed state and final machining. The shells are additionally fixed with fixing protrusions included in the recesses located on the neck located at the places of least loading, the protrusions being placed in the area adjacent to the joints of the shells and made by thermoplastic deformation, and the depressions on the outside are filled by welding. Compression of the shells is carried out using shoes with high thermal conductivity. Fillet protect during welding technological plates, which are removed during hot welding seams (AS No. 1597256, V23P 6/00).

The disadvantages of this method are:

1. The inability to create a given interference between the repair shell and the neck of the shaft.

2. Creating a recess on the neck is not technologically advanced, since it must be performed on a surface having a hardness of HRC 50 ... 60.

3. The method is not suitable for the use of thin-walled shells due to its unreliable fixation on the shaft neck. The closest analogue to the claimed method relates to a method for restoring a crankshaft, including machining the necks with technological deepening into the body of the surface to be restored across the entire width between the neck cheeks with the formation of fillets, tightening on the machined necks of overlays compensating metal wear in the form of a split ring or half rings and their subsequent grinding to the nominal size, while after machining the crankshaft is subjected to high tempering, for which I put t in a cold oven, heated for 3 ... 4 hours to t = 500 ... 600 ° C, kept at this temperature for 4-6 hours, and then cooled together with the furnace, while through the split rings holes with a diameter of 5 ... 7 mm and fix the rings on the machined necks by welding their joints, boiling them with the neck of the shaft, the weld is placed in a zone limited to 25-50 ° of crankshaft rotation from the top dead point of the restored connecting rod, the weld is cooled to ambient temperature with a tightness of a split ring 0 .1 ... 0.15 mm, and then the hole of the split ring with the neck of the shaft, which is located opposite the weld, is first boiled, and the remaining holes are boiled, symmetrically approaching the weld, using split rings of width b, length L and thickness δ:

b = L _w -2r- (1 ... 2) mm,

L = πd _b + (2 ... 4) mm,

δ _L = δ _L.ost. + δ _L.R. + δ _l.s. + δ _L.

where L _W - the width of the neck of the shaft between the cheeks;

r is the fillet radius;

d _b is the calculated diameter of the pre-treated reconditioned neck;

δ _l - the thickness of the split ring to restore the neck to the nominal size;

δ _L.R. - the thickness of the split ring, compensating for all repair dimensions;

δ _l.s. - the thickness of the split ring, compensating for the maximum wear of the shaft neck at the last repair size;

δ _lost - the residual thickness of the split ring, necessary to ensure the mechanical strength of the split ring at the final stage of shaft operation;

δ _lshl is the allowance for the thickness of the split ring for grinding to the final size, and the half rings are fixed on the machined necks by welding the joints, boiling them with the neck of the shaft, and the first weld is located in a zone limited by 25-50 ° of crankshaft rotation from the top the dead center of the reconstructed connecting rod neck, and the second seam is relative to the first with a 180 ° rotation (Pat. RF No. 2235009, B23P 6/00, F16C 3/6).

The disadvantage of this method is:

1. The inability to create a strictly defined interference between the plate and the neck of the shaft.

The objective of the invention is the creation of a strictly defined interference between the plate and the neck of the shaft.

The problem is achieved due to the fact that the shaft restoration method, including machining the shaft necks with technological deepening into the shaft body over the entire width of the surface being restored with the formation of fillets, a preload installation on machined necks that compensate for the wear of the metal plates in the form of a split ring or half rings securing the pads on the machined necks by welding their joints to produce a butt weld and boiling the pads with the shaft journal, then cool with ykovoy weld to ambient temperature and produce the installation surface linings on both sides of the butt weld elektrozaklepok and subsequent grinding necks in nominal or repair dimensions, wherein the used inserts, width b, the length L and δ _l a thickness which is determined from the following mathematical expressions:

b = L _w -2r- (1 ... 2) mm,

L = πd _b + (2 ... 4) mm,

δ _L = δ _L.ost. + δ _L.R. + δ _l.s. + δ _L.

where L _W - the width of the neck of the shaft;

r is the fillet radius;

d _b is the calculated diameter of the machined reconditioned neck;

δ _l - the thickness of the lining for the restoration of the neck in a nominal size;

δ _L.R. - a value that compensates for all repair dimensions of the neck;

δ _l.s. - a value that compensates for the maximum wear of the shaft journal at the last repair size;

δ _lost - the residual value of the thickness of the lining, necessary to ensure the mechanical strength of the lining at the final stage of shaft operation;

δ _lshl is the allowance for the thickness of the grinding pad to the final size, after installing the pad on the shaft neck with a preload, it is evenly squeezed across the entire surface, while the pad made in the form of a split ring is heated to a temperature t ° before welding its joints:

,

,

where N is the required interference in the mating of the shaft journal - plate after welding the plate to the shaft journal;

α is the coefficient of linear expansion of the lining material;

- длина окружности шейки вала,

- the circumference of the neck of the shaft,

and the joint in the form of half rings welds the joint of the half rings to obtain the first butt weld, after which the patch is heated to a temperature of t °:

,

,

where t ⁰ _{W. in} - the temperature of the neck of the shaft after boiling the first axial butt weld, and weld the joint of the half rings to obtain a second butt weld.

New significant features:

1. Install the pad on the neck of the shaft and evenly compress it over the entire surface.

2. Heated pad made in the form of a split ring to a temperature

,

,

where N is the required interference in the mating shaft journal - plate, after welding the plate to the shaft journal,

α is the coefficient of linear expansion of the lining material,

- длина окружности шейки вала.

- the circumference of the shaft journal.

3. At the plate, made in the form of half rings, boil the first axial butt weld and heat to a temperature:

,

,

where t ° _b.w. - the temperature of the neck of the shaft after boiling the first axial butt weld, and weld the joint of the half rings to obtain a second butt weld.

. При проваривании осевого стыкового сварного шва происходит образование локальной ванны, которая не будет натягивать накладку. Осевой стыковой сварной шов быстро охлаждается из-за большой массы шейки вала, и дополнительное внесение теплоты в кромки накладки вдоль осевого стыкового сварного шва не приведет к заметному изменению натяга после остывания накладки. При остывании длина накладки уменьшается на величину

, равную удлинению при нагревании накладки до температуры t°.When using this method, it is possible to obtain the required design interference between the cover plate and the shaft journal. When using an overlay in the form of a split ring, it is mounted on the neck of the shaft, uniformly crimped over its entire surface and heated to the design temperature and boiled axial butt weld. When heated to a predetermined temperature, the lining length increases by

. When boiling the axial butt weld, a local bath forms, which will not stretch the overlay. The axial butt weld is quickly cooled due to the large mass of the shaft journal, and additional heat input to the edges of the plate along the axial butt weld will not lead to a noticeable change in the interference fit after cooling of the plate. When cooling, the lining length decreases by

equal to the elongation when the lining is heated to a temperature of t °.

As a result, we obtain the required interference in the pairing:

N = D _vn -d _w

where D _VN is the internal diameter of the welded plate after cooling;

d _W - the diameter of the neck of the shaft.

When using two half rings as a lining, they are installed on the shaft journal with uniform compression over their entire surface and the first axial butt weld is welded, then the lining is heated to:

,

,

where t ° _b.w. - the temperature of the neck of the shaft after welding the first axial butt weld and boil the second axial butt weld.

To obtain a given interference fit, it is necessary to take into account the increase in the size of the shaft neck after the first axial butt weld is welded by introducing the temperature of the shaft neck heating t ° _b.w. .

This method can be applied in the manufacture of shafts. In this case, the billet of the crankshaft is made of low carbon steels. The required wear resistance of the finished shaft will be obtained at the last stage of its manufacture by welding, according to the proposed method, hardened thin-walled plates made of high-quality carbon steel.

With this manufacturing method, expensive heat treatment operations of all the shaft journals are not required, which significantly reduces the fatigue strength of the entire shaft, which reduces the shaft service life.

Figure 1 schematically shows the neck of the shaft with an overlay.

Figure 2 - scan lining.

Figure 3 - section aa of the neck of the shaft with an overlay in the form of a split ring (I) and in the form of half rings (II).

The shaft neck contains a cylindrical part 1 and a covering plate 2, in which holes 3 with a diameter of 5 ÷ 7 mm for electro-rivets, a hole 4 for supplying lubricating oil, fillets 5, ring welds 6, welded from above the edges along the edge of the working surface 7 of the plate can be made 2. A weld seam 8 connects the joints of the plate 2. The plate 2 can be made in the form of a split ring or half rings, both with holes 3 for electric rivets and without them, if electric contact welding is used. In this case, the center of the hole 3 is also the center of electrical welding.

With a lining width of up to 50 mm, electric rivets are installed in one row along the line of symmetry. With a width of more than 50 mm - in two rows or in a checkerboard pattern, i.e. with the displacement of one row relative to another. The distance from the center of the holes 3 to the edge of the lining 2 is a = 15 ... 20 mm, and the distance c from the junction of the plate 2 to the center of the nearest hole 3 is at least 15 mm. The width of the lining in the form of a split ring is calculated by the formula:

b = L _w - 2r- (1 ... 2) mm,

where L _W - the width of the neck of the shaft;

r is the fillet radius;

(1 ... 2) mm - technological gap between the split ring and the fillet.

Band Length L

L = πd _b ,

where d _b is the calculated diameter of the pre-treated reconditioned shaft journal.

The thickness of the lining δ _l for restoring the neck to the nominal size includes a value that compensates for all repair dimensions δ _l.r.p. (0.5 mm), a value that compensates for the maximum wear of the neck of the shaft at the last repair size δ _l.r.r.r. (0.1 ... 0.15) mm, residual lining thickness required to ensure mechanical strength of the lining at the final stage of shaft operation

δ _lost (0.5 ... 1.0) mm and an allowance for the thickness of the grinding pad to the final size (0.25 ... 0.50) mm.

For a typical calculation of the thickness of the lining, ensuring the restoration of the neck of the shaft to the nominal size,

δ _l = 0.5 + 0.1 + 0.5 + 0.5 = 1.6 mm

To determine the thickness of the lining, ensuring the restoration of the shaft neck to a repair size, its value is reduced by the corresponding repair size:

δ _L.R. = δ _L.R. Δ _w / 2,

where Δ _W - reducing the diameter of the neck of the shaft for the corresponding repair size.

The residual value of the thickness of the lining δ _l. includes a defective layer of the surface of the neck with cracks, burns, etc.

If the defective layer exceeds the set value of the lining thickness δ _l. , then the defects are eliminated by welding or the shaft is rejected.

Before restoration of the shafts, preparatory operations are carried out: disassembly and washing, determination of the technical condition of the shaft after operation: the presence of cracks, control of the neck hardness, and dressing.

The shaft is edited by chasing by introducing compressive stresses into the fillets of 5 necks from the side of the concave central axis. Then, grinding and polishing of the necks and fillets 5 is carried out to the calculated size (usually: less than 0.5 ... 1.5 mm of the last repair size, thereby removing the metal layer with cracks located in it).

Made of steel tape with a thickness of δ _l. <2 mm pads in the form of a split ring 2 or for large tape thicknesses (more than 2 mm) pads in the form of half rings. Why cut the strip into the estimated dimensions:

Split Ring Width:

b = L _w -2r- (1 ... 2) mm,

where L _W - the width of the neck of the shaft;

r is the fillet radius;

(1 ... 2) mm - the technological gap between the plate and the fillet.

The length of the tape for the lining in the form of a split ring:

L = πd _b ,

where d _b is the calculated diameter of the pre-treated reconditioned shaft journal.

The length of the tape for the lining in the form of two half rings:

L = πd _b .

Bend the strip into a split ring 2.

Then, on rolled rings 2, holes 4 are drilled for the lubricating channel and electro-rivets 3, the diameter of the latter is 5-7 mm. With a width b of the lining 2 to 50 mm, electric rivets are installed in one row along the neck line of symmetry. With a tape width of more than 50 mm - in two rows symmetrically or in a checkerboard pattern, i.e. with the offset of one row relative to another. In this case, the distance from the center of the holes 3 to the edges of the lining should be 15 ... 20 mm, and the distance from the joint of the lining to the center of the nearest hole should be at least 15 mm. Then, using the elastic properties of the lining 2, it is unclenched and put on the neck of the shaft with a preload due to the fact that the inner diameter of the lining 2 is less than the outer diameter of the restored neck, and a gap of 4 ... 5 mm is obtained. If you use an overlay in the form of half rings, then in both joints the gap will be 4 ... 5 mm each.

Combine the lubricating holes 4 in the journal of the shaft and the lining 2 and pre-fix. After that, the overlay 2 is uniformly pressed across its entire surface to the body of the shaft journal. Then heat the pad 2 (in the form of a split ring) to

measuring her temperature with a pyrometer.

; α=11,8·10^-6 Example. The neck of the shaft with a diameter of d _W = 100 mm. When welding the lining 2 in the mating neck - the lining, it is necessary to create an interference fit N = 0.05 mm. Lining material - steel 65 G,

; α = 11.8 · 10 ^-6

,

,

therefore, the pad 2 must be heated to t ° - 42.3 ° in order to obtain an interference fit N = 0.05 mm.

Then weld the joints of the lining 2, for example, by semi-automatic arc welding in a CO ₂ medium by axial, butt weld 8.

When two half rings are used as a lining, they are mounted on the neck of the shaft, uniformly crimped, and the first axial butt weld is boiled. Then the half rings are heated to the temperature necessary to create a given interference fit, and the second axial butt weld is boiled.

For example, the neck of the shaft d _W = 100 mm heated to 50 ° C. We determine how much the diameter of the shaft neck has increased and what additional temperature it is necessary to heat the half rings.

where d _h - neck diameter after heating;

β is the coefficient of expansion of the cross-sectional area of the neck of the shaft;

F is the cross-sectional area of the shaft neck;

t ° is the heating temperature of the shaft journal;

d _w - the diameter of the neck of the shaft before heating,

The increase in the diameter of the neck of the shaft during its heating by 50 ° C amounted to

Δd _W. = d _bn -d _w

To compensate for the increase in shaft diameter, additionally heat the half rings before welding to the shaft journal

Therefore, to obtain the required interference in the coupling of the half ring - the shaft neck, it is necessary to heat the half rings

t ° _add. - equal to the heating temperature of the neck of the shaft during the welding of the first axial butt weld. The half rings are heated to t ° ₁ and the second axial butt weld is boiled.

, то и при остывании она уменьшится на ту же величину

. После чего заваривают отверстия 3 в накладке 2, приваривая ее к шейке вала, создавая, таким образом, электрозаклепки, дополнительно фиксирующие накладку 2 на шейке вала. При этом первую заклепку ставят, например, в отверстие 3 в обе стороны от осевого стыкового сварного шва на расстоянии не менее 15 мм. Последующие электрозаклепки устанавливают с шагом 20...30 мм. После чего приваривают кольцевыми сварными швами 6 сверху края по кромке рабочей поверхности накладок 2 к телу шейки вала 1. После чего проводят зачистку сварных швов и шлифованием, и полированием шеек в заданный размер. Затем методом дефектоскопии убеждаются в отсутствии сварочных трещин.Cool the axial butt weld 8 or 8, 9 to t ° environment. In this case, the required interference is obtained in conjunction with the pad - the shaft neck, because pad length 2 increased by

, then when cooling it decreases by the same amount

. After that, the holes 3 are welded in the plate 2, welding it to the neck of the shaft, thus creating electric rivets, additionally fixing the plate 2 on the shaft neck. In this case, the first rivet is placed, for example, in the hole 3 on both sides of the axial butt weld at a distance of at least 15 mm. Subsequent electrical rivets are installed in increments of 20 ... 30 mm. Then welded by circular welds 6 from the top edge along the edge of the working surface of the plates 2 to the body of the neck of the shaft 1. Then they clean the welds and grinding, and polishing the necks to a predetermined size. Then, using flaw detection, they verify that there are no welding cracks.

Claims (1)

A method of shaft restoration, including machining the shaft necks with technological penetration into the shaft body over the entire width of the surface to be restored with the formation of fillets, preloading the treated pads on the machined necks in the form of a split ring or half rings, fixing the pads on the machined necks by welding them joints with obtaining a butt weld and boiling plates with a neck of the shaft, then cool the butt weld to ambient temperature s and make installation on the surface of the plates on both sides of the butt weld of electric rivets, and then grinding the necks in the nominal or repair dimensions, using the plates, width b, length L and thickness δ _l which are determined from the following mathematical expressions: b = L _w -2r- (1 ... 2) mm, L = πd _b + (2 ... 4) mm, δ _L = δ _L.ost. + δ _L.R. + δ _l.s. + δ _L. where L _W - the width of the neck of the shaft; r is the fillet radius; d _b is the calculated diameter of the machined reconditioned neck; δ _l - the thickness of the lining for the restoration of the neck in a nominal size; δ _L.R. - a value that compensates for all repair dimensions of the neck; δ _l.s. - a value that compensates for the maximum wear of the shaft journal at the last repair size; δ _lost - the residual value of the thickness of the lining, necessary to ensure the mechanical strength of the lining at the final stage of shaft operation; δ _lshl - allowance for the thickness of the grinding pad in the final size, characterized in that after installing the pad on the shaft neck with a preload, it is uniformly squeezed across the entire surface, the pad made in the form of a split ring is heated to a temperature t before welding °:

, where N is the required interference in pairing the shaft journal — the plate after welding the plate to the shaft journal; α is the coefficient of linear expansion of the lining material;

- the circumference of the neck of the shaft, and the joint in the form of half rings welds the joint of the half rings to obtain the first butt weld, after which the patch is heated to a temperature of t °:

, where t ° _w.v is the shaft neck temperature after boiling the first axial butt weld, and the joint of the half _rings is welded to produce a second butt weld.

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