RU65593U1 - SHAFT, PREFERREDLY, SUBMERSIBLE PUMP - Google Patents

Abstract

A useful model is a shaft, mainly a submersible pump, subjected to prolonged exposure to torsional and bending moments, including pulsed in the presence of aggressive media, and can be used in the oil industry as a shaft of a submersible pump, a gas separator shaft, a hydraulic protection shaft, and in other machines and mechanisms operating in similar conditions. The technical task is to clarify the design characteristics of the shaft, increasing the strength and toughness of the material for its manufacture. The solution of this problem is achieved by the fact that when calculating the strength of the shaft or when checking the correct choice of material for its manufacture, the diameter of the shaft in any section satisfies two maximum permissible stresses, which are selected as the tensile strength in bending with a working aggressive fluid and the limit the fluidity during torsion of the shaft material, while the torque in the first case corresponds to the steady state operation of the pump, in the second - not less than 2.5 times the magnitude of this twisting th instant, and it is used for manufacturing a shaft mild, high strength stainless steel and a viscous component ratio, wt.%

and the amount of Ni _equiv. = 22.3 ± 2.5-0.8 Cr _equiv

Using the utility model allows to increase the survivability of the shaft of a submersible pump by choosing the right shaft diameter and material for its manufacture.

Description

A useful model is a shaft, mainly a submersible pump, subjected to variable torque and bending moments, designed for long-term operation in an aggressive environment with the presence of aqueous solutions of chlorides, hydrogen sulfide, salts, oil products, in combination with elevated temperature and can be used in the oil industry, for example, as a shaft of a submersible pump, a gas separator shaft, a hydraulic protection shaft, as well as in other machines and mechanics zmah working in such conditions.

A known shaft design is subjected to alternating loads, for which billets are used with special surface treatment, with recesses on the surface for the location of various parts (see "Vane Pumps", Mikhailov AK, Malyushchenko VV, "Engineering ", 1977, pp. 194-202)

The closest of the identified analogues selected for the prototype is the shaft of a submersible pump, subjected to prolonged exposure to torque with bending and 2-3-fold instantaneous overloads, with recesses on the surface to accommodate connecting or fixing parts and splines (see. "Calculation and design oilfield equipment ”, Chicherov L.G., Molchanov G.V., Rabinovich AM et al., M,“ Nedra ”, 1987, pp. 35-44, 146-152).

The disadvantage of the prototype, as well as the analogue, is the insufficient reliability of the submersible pump, due to inaccurate selection

the diameter of the shaft when calculating the strength. When calculating the strength, the shaft diameter is selected depending on the value of the yield strength of the material of the shaft, which is determined by tension, while the shaft operates in bending torsion, with the introduction of a safety factor to account for metal fatigue. When choosing the material of the product, preference is given to steels with a higher endurance limit according to reference data, at best - according to the results of tests in a standard aggressive environment. The actual working environment differs significantly from the standard in its multicomponent nature - the presence of salts, chlorine ions, dissolved hydrogen sulfide, hydrocarbons, pH, and these characteristics are different in different fields. Therefore, the introduction of a safety factor to take into account the influence of metal fatigue and aggressiveness of the working medium does not allow one to choose the shaft diameter correctly, since with a small margin it can lead to insufficient reliability of the shaft in operation - premature failure from fatigue, with an excess margin - to overuse of metal, reduce the economic characteristics of the pump, because an increase in shaft diameter by 8-10% reduces the efficiency of the pump by 4-6% (see. "Calculation and design of oilfield equipment", Chicherov LG, Molchanov GV, Rabinovich AM et al., M., "Nedra ", 1987, p. 146). Issues related to the reliability of the shaft under pulsed loads are not considered.

The technical problem solved by the utility model is to clarify the design characteristics of the shaft, increase the strength and toughness of steel for the shaft of a submersible pump. The problem is solved in that to the shaft of the submersible pump, with the unreliability of which during operation is associated with 40% failures of the entire unit [see Kudryashov SI “Improving the reliability of ESP submersible systems” - “Oil Industry”, 2005, 6.1 26], were treated as a special technique, for reliable operation of which the main requirement is to bring the test conditions of materials closer to

to the workers. In this regard, the design of shafts for submersible pumps or to verify the correct calculation and selection of shaft material, calculated according to the generally accepted methodology, is carried out using the results of tests of the shaft material under conditions that are closest to operational. It is assumed that the effect of the load on the shaft can be divided into two stages:

- at a steady state pump operation, when the shaft has been operating for a long time under conditions of corrosion fatigue during torsion with bending,

- short-term operation with impulse torque overloads.

At the first stage, the reliability of the shaft material is evaluated by the endurance limit determined on the samples during torsion with bending under the temperature-corrosion conditions of the working fluid.

The value of the endurance limit largely depends on the numerous parameters of aggressiveness of the working fluid, which differ in different fields (see Re-purchase of A.G. et al. “Calculation of the corrosiveness of the medium in the design of field pipelines”, “Oil industry”, 2005, 6, 130). Therefore, before the accumulation of the necessary reference material, in order to comply with the conditions for modeling operating conditions, fatigue tests should be carried out in the working fluid of the field for which the pump is intended.

The endurance limit is much less than the yield strength of the material, and being in the elastic region it is a stress below which no foci of metal damage are formed [see “Metallurgy and heat treatment of steel” vol. 1, M. Metallurgy, 1983, pp. 226-234] . Therefore, the minimum shaft diameter determined when calculating the strength of the endurance limit as the maximum allowable voltage

provides shaft reliability at the first stage of operation and does not require safety factors.

At the first stage - at a steady state pump operation, the torque is calculated by the formula:

M _mouth = M _n + M _t

where M _n is the moment on the shaft at a steady speed corresponding to the maximum pump power and is determined by the well-known formula associated with the magnitude of the pressure and fluid supply through the number of stages of the pump and the power of the stage (see analog):

M _n = 974 * N _max * z / n, where

N _max - power pump stage,

n is the number of revolutions of the shaft at maximum pump power,

z is the number of stages of the pump.

M _t - the moment spent on overcoming the friction forces in the pump.

Calculations show that MT at the first stage of pump operation, the value is small and equal to 0.4-0.6 kgm.

At the second stage, when pulsed short-term overloads of torque occur during pump start-up, when rock particles clog the working fluid during erosion of the formation, and other similar influences, the shaft works on torsion and the shaft diameter is determined by the maximum allowable stress, for which the yield strength at torsion, more precisely, the value of 0.9 _t , because the shaft is calculated to work in the elastic region of stress, and the yield strength corresponds to the onset of plastic deformation equal to 0.3%. The torque should not be lower than the starting torque of the pump, which is taken as the lower limit of M _imp .

M _start = M _s + (M _dmah- M _s ) * I _n / I _n + I _d , (see Chicherov L.G. et al., Calculation and Design of Oilfield Equipment, M, Nedra, 1987, 146 -152), where

M _with - the moment of resistance of the pump at a shaft speed corresponding to the maximum moment of the electric motor;

M _s = (M _n -M _t ) (n _m / n) ² + M _t , where

n _m is the shaft speed corresponding to the maximum moment of the electric motor; n _m - 2000 rpm

n is the shaft speed at maximum pump power;

n - 2820 rpm.

M _dmah - maximum torque on the motor shaft (passport data)

I _n - moment of inertia of the pump;

I _d - the moment of inertia of the rotor of the electric motor.

Calculations show that M _start ≤2.5 M _mouth

The minimum shaft diameter for each of the stages is determined according to well-known formulas for finding the values of tangential and normal stresses (see Ivanov MN "Machine Details", M. Higher School, 1984, 261). At the same time, it is taken into account that normal stresses arising at the spline ends of the shaft due to misalignment of the assembly of pump sections are insignificant and can be neglected. Therefore, for the first stage of the shaft:

where

W _p is the polar moment of inertia of the shaft;

M _mouth - torque corresponding to the steady state operation of the pump;

; ;

For grooves and slots:

; where

D is the diameter of the shaft,

d is the diameter of the undercut or the average diameter of the splines.

t _-1 - endurance during torsion,

k is the coefficient of sensitivity to stress concentration depending on the radius of curvature in the recesses and slots and the tensile strength of the shaft material (see, for example, Zolotarevsky B.C. "Mechanical properties of metals", M, Metallurgy, 1983, 3.10).

Similarly, for the second stage of the shaft operation - with pulse overloads:

where

; where

M _imp ≥2.5 M _mouth ; t _t - yield strength during torsion.

From the two values of the minimum diameter obtained for fatigue loading at a steady-state pump operation mode and for torsion under impulse torque overload, a large value is selected and the safety factor is checked against the ratio of the allowable stresses to the calculated for each stage, while the selected allowable stresses should be more calculated in any section of the shaft.

To obtain high values of the endurance limit in an aggressive working fluid and the yield strength during torsion, the choice of structure and alloying of steel is important. The main material for shafts of submersible pumps for more than twenty years is viscous stainless steel 03X14H7B with a martensitic-ferritic structure, the strength of which, as practice shows, is not enough with increasing well depth and impulse loads.

Declared in a utility model, stainless steel in the Sheffler structural diagram (see Gulyaev A.P. Metallurgy, M. Metallurgy, 1977, 486), occupies the region Cr _equivalent / Ni _equivalent <1.7. As is known (see Werkstoffkunde Stahl. Band 2.1985, Springer - Verlag, 404), the Cr _eq values form all ferrite-forming elements entering the steel with their equivalence coefficients in comparison with Cr, namely: Cr _eq = Cr + 1.5Si + 1 , 4Mo + 2Ti + 2Al. Similarly, Ni _eq values form all austenitic-forming elements contained in steel with their equivalence coefficients in comparison with Ni:

Ni _equiv = Ni + 30C + Cu + 0.5Mn.

At a content of Ni _equiv = 22.3 ± 2.5-0.8 Cr _equivalent, all steels with a ratio of Cr _equivalent / Ni _equivalent <1.7 have a martensitic-austenitic (M + A)

structure with varying amounts of martensite and austenite. This expression is the equation of a family of straight lines in the structural diagram, where the value of 22.3 ± 2.5 corresponds to the amount of Ni _equiv in steel in the absence of ferrite-forming elements, and the coefficient at Cr _equiv = 0.8 is the tangent of the angle of inclination to the abscissa of the lines, bounding the region (M + A) of the steels in the diagram.

The martensitic-austenitic structure of steel corresponds to the highest viscosity and strength of steel, depending on the amount of martensite and austenite, because Martensite plates with a carbon amount of not more than 0.03% turn out to be surrounded by thin viscous layers of austenite, delaying the development of germ cracks. With the ratio of CR _equiv. / Ni _equiv ≥1.7 in the steel, ferrite appears and the larger the quantity, the greater the value of this ratio. The presence of ferrite in the martensitic or (M + A) - structure leads to a decrease in strength characteristics and an increase in the critical temperature of brittleness, which impairs the fatigue strength and toughness of steel.

The martensitic structure, especially with the precipitation of dispersed particles of intermetallic or excess phases during aging of steel, leads to high strength. To harden martensite with dispersed intermetallic particles, Ti, Al, Mo are present in steel, which in the presence of Ni form the phases Ni ₃ Ti, Ni ₃ Al, Ni ₃ (Ti, Al), Ni ₃ Mo. With the lower limits of the Ti, Al, Mo content indicated in the utility model, there is no effect of these elements on hardening. The upper limits of the content of these elements correspond to the maximum atomic concentration of these elements in the intermetallic phases, linking the amount of nickel that is acceptable for maintaining the required viscosity of steel. In addition, the presence of Ti and Al provide a fine-grained structure, because during the crystallization of steel, Al binds nitrogen to stable nitrides, and Ti forms stable TiC carbides uniformly distributed in

the volume of grains, and protects the steel from intergranular corrosion due to the formation of unstable chromium carbides along the grain boundaries. A Ti content of less than 0.01% is not sufficient to bind carbon in steel. The content of Ti and Al of more than 0.8% is excessive, because binds a significant amount of Ni to intermetallic compounds and leads to a decrease in toughness.

The carbon content of the steel for the formation of martensite high viscosity should be as low as possible. The upper limit of the amount of carbon 0.03% is determined by the technological possibility of steelmaking. In addition, low carbon stainless steels are less prone to intergranular corrosion.

Nickel is the main element that determines the viscosity of steel and forms the austenitic component of the structure depending on the number of ferrite-forming and austenite-forming elements in the ratio Ni _equiv = 22.3 ± 2.5-0.8 Cr _equivalent . When the amount of Ni is less than 4% with a ratio of Cr _eq. / Ni _equiv <1.7, a martensitic structure is obtained with a small amount of residual austenite, with high strength, but with insufficient viscosity. When the amount of Ni is more than 12% and the ratio of CR _equiv. / Ni _equiv. <1.7, only an austenitic structure with high viscosity and low strength is formed.

Steel for shafts of submersible pumps must withstand fatigue failure in a corrosive environment, therefore, the minimum chromium content or amount (Cr + 3.3Mo) should be higher than the threshold value of the electrode potential corresponding to 12% Cr in the absence of molybdenum. In the presence of Mo, the lower limit of the amount of Cr according to the anticorrosion characteristics of steel is at the level of 8%. With a minimum amount of Cr, up to 12%, and a minimum amount of Ni, the steel has a martensitic structure with a small amount of residual

austenite, with high strength and insufficient viscosity. With an increase in the amount of Ni, the fraction of the austenitic component increases, and the viscosity of steel increases with a decrease in strength. The upper limit of the amount of Cr is taken to be 17%, exceeding which with a minimum amount of Ni, a ferritic component appears in the steel structure with a decrease in strength. The appearance of a ferritic component in the structure is extremely undesirable, because It is at its borders that the brittle σ phase can form and the steel resistance to brittle fracture decreases, which is especially dangerous under the action of a pulsed load. With an increase in the amount of Ni and an upper limiting Cr content, the structure becomes austenitic with high viscosity and low strength.

Molybdenum, like chromium, promotes the appearance of a passivating film that protects steel from corrosion, especially in the presence of copper, and is involved in the formation of intermetallic hardening phases with nickel and cobalt. When the amount of Mo is less than 0.05%, its effect is practically absent. The upper limit of 3% is due to a decrease in its effect on hardening and corrosion resistance of steel, as well as the high cost of molybdenum.

Copper forms dispersed particles of an excessive hardening phase during aging, and the fields of elastic stresses during their formation contribute to a greater dispersion of intermetallic phases such as Ni ₃ (Ti, Al), etc. With a lower limit of 0.3% copper content, its effect is practically absent, the upper limit is 5 % corresponds to its maximum solubility in austenite.

The presence of cobalt in the steel composition contributes to its significant hardening, because Co forms dispersed CoMo and CoCr phases with Mo. At the same time, Co promotes an increase in interatomic bonding forces and delays the dissociation of carbide and other phases, which positively affects the resistance of steel in corrosive environments with the presence of dissolved hydrogen sulfide. The lower limit of cobalt content of 0.01% corresponds to the absence of its noticeable

influence. The upper limit of 5% is due to a significant rise in price of steel, as It is expensive and requires an increase in the amount of Ni to ensure an adequate supply of steel viscosity.

The amount of sulfur and phosphorus in the steel is kept at the lowest technologically achievable level - less than 0.025%, to ensure the minimum embrittlement associated with these impurities. The presence of Si and Mn in a residual amount of less than 0.8% ensures sufficient steel deoxidation.

A small amount of 0.005-0.2% nitrogen, which as an austenitizing element, can increase the amount of austenite in steel and thereby reduce the content of expensive nickel, can be introduced into steel. A nitrogen content of less than 0.005% does not affect the structure formation. The introduction of nitrogen of more than 0.2% in the presence of Ti and Al leads to a deterioration in ductility due to the formation of a large amount of nitrides.

To reduce the tendency to intergranular corrosion, Nb is additionally introduced into the steel, which, like Ti, binds carbon, forming dispersed NbC particles located in the grain volume, protecting the grain boundaries from chromium depletion. The introduction of 0.5% Nb completely binds carbon. When the Nb content is less than 0.05%, its effect is practically not felt.

The introduction of Ca into steel in an amount of up to 0.01% by calculation provides the formation of globular sulfur compounds to improve machinability by cutting.

The introduction of boron to 0.005% of the calculation helps to reduce the amount of sulfur and phosphorus along the grain boundaries with a beneficial effect on the viscosity of steel.

An example of using a utility model.

We checked the correct calculation of the shaft diameter and the choice of material for its manufacture in a submersible pump ESP 5-50-2000, which failed due to a cut of the splined end of the shaft of the lower section of the pump. Shaft material - steel 03X14H7 V, shaft diameter

17 mm, the inner diameter of the splined end 14 mm, the number of splines 6. mechanical characteristics of steel: σ _t = 85 kg / mm ² ; σ _in = 100 kg / mm ₂ ; δ = 14%; ψ = 58%; KCU ₊₂₀ = 15.8 kgm / cm ² ; yield strength in torsion t _t = 52 kg / mm ² ; endurance limit to bending torsional based on the 10 ⁷ cycles in the working fluid deposit Purpe σ _-1 = 24,5 kg / mm ^2;

Torque acting on the pump shaft during steady state operation:

.

With steady state pump operation, the shaft runs to fatigue. Tangential stresses arising in the spline end of the shaft.

Due to the possible misalignment of the assembly of the sections, a bending moment may be applied to the splined end of the shaft, caused by a force of up to 60-100 kg. Bending stress on the splined end of the shaft:

Where L is the distance from the middle of the slot to the bearing.

Equivalent stress under normal and shear stresses .

Thus, under corrosion-fatigue loading, only tangential stresses act, which should be less than the allowable stress, which is used as the endurance limit of steel in a real environment:

t _mouth <[t] <t _-1 , i.e. 23.94 kgf / mm ² <24.5 kgf / mm ²

It follows that the splined end of a shaft with a diameter of 17 mm from steel 03X14H7V withstands the effect of corrosion-fatigue loading under steady state conditions, but almost at the limit of the possible, because safety factor.

When starting the pump, taking into account the resistance of the friction forces acting in the pump and the total moment of inertia of the impellers, shaft, bushings and rotor of the electric motor, the shaft experiences a dynamic load:

;

Pump Resistance Torque

Moment of inertia of the pump

I _n = I _pk + I _a + I _W * = 7.0626 kgm ² s

The moment of inertia of the rotor of the electric motor:

After substituting all the values for ESP 5-50-2000, we get;

Pump overload

Under the influence of pulsed torque taking into account

at start-up, the shaft is twisted and the condition must be met:

t _start <[t] <0.9 _t

Margin of safety at start-up:

,

those. the tangential stresses at start-up exceed the permissible ones.

Consequently, the splined end of the shaft cannot withstand the starting overload, and under the action of shear stresses, even when the pump starts, plastic deformation of the splines can begin with

further failure of the shaft. Thus, a shaft with a diameter of 17 mm made of steel 03Kh14N7V for the UETsN5-50-2000 pump is designed for strength incorrectly and cannot withstand pulsed overloads with a multiplicity of more than 2.3. It is necessary to use a shaft of a larger diameter, or to use steel with a higher yield strength during torsion.

In order to optimize the choice of steel for the shaft of a submersible pump in accordance with the declared chem. the composition and ratio of the components were smelted pilot melts, the compositions of which are shown in table 1 together with steel 03X14H7B. Steel was smelted in an electric arc furnace. Ingots weighing 1.15 tons were cast, which were squeezed in blooming into a square of 100 mm, and then in a continuous mill 250 they rolled into rods with a diameter of 19 mm. The rods were subjected to double tempering at a temperature of 740 ° and 540 ° C with a holding time of 3 hours. Samples were cut from rods to determine mechanical tensile properties according to GOST 1497-84, impact strength according to GOST 9454-78, torsion tests according to GOST 3565-80 and fatigue according to GOST 25.502-79. The test results are shown in table 2.

Compositions No. 2, 3, 4, 5, 7 - satisfy the requirements of the claimed model, namely: KCU ₊₂₀ °> 7 kgf / cm ² and yield strength at break 115-150 kgf / mm ² . The optimal composition is No. 5. In composition No. 1, Cr was introduced slightly above the upper limit, due to which the ratio Cr _equivalent / Ni _equivalent > 1.7 was obtained and an austerite-ferritic-martensitic structure with low strength, low impact strength and fatigue resistance was formed in steel. In composition No. 6, due to the high content of Cr and Cu at the upper limit, a (M + A) structure is formed with a large amount of austenite, low strength, high viscosity and low fatigue resistance. Composition No. 10 with a high Cr content has Ni at the lower limit, the ratio of Cr _equivalent / Ni _equivalent > 1.7, there is a structure of martensite with austenite and ferrite with a sufficiently high strength, low viscosity and low fatigue resistance. Composition No. 9 has Ni below

lower limit and in spite of the low Cr content, a ratio of Cr _equivalent / Ni _equivalent > 1.7 is obtained, steel has reduced characteristics of strength, toughness and fatigue resistance. Composition No. 8 has Cr at the lower limit, Ni at the upper limit, but the Ti and Al content is higher than the upper limit, due to which Ni was bound into intermetallic compounds, as a result, the steel has high strength but low viscosity.

If we use one of the experimental compounds as the material of the shaft with a diameter of 17 mm, for example, inexpensive composition No. 3, corresponding to steel 03X14N5D4B and substitute the values of the mechanical properties of this composition into the calculation formulas for estimating the shear stresses, we obtain:

t _mouth <[t] <t _-1 , i.e. 23.94 kgf / mm ² <32 kgf / mm ² .

The safety factor of the splined end of the shaft made of steel of composition No. 3 under corrosion-fatigue loading at the stage of steady-state operation:

To _mouth = [t] / t _mouth = 32 / 23.93 = 1.34.

This is significantly more than the steel 03X14H7V (K _mouth = 1,024).

Tangent stresses arising in the splined end of the shaft made of steel of composition No. 3, taking into account overload during pulsed loading, component 2.5 M _mouth :

t _imp = M _imp / W _p = 2.5 * 15.94 / 0.666 = 59.83 kgf / mm ²

Safety factor in the splined end of a shaft made of steel of composition No. 3 under pulsed loading:

To _imp = [t] / t _imp = 0.9 * 72 / 59.83 = 1.083.

This is a very satisfactory result compared to a shaft made of steel 03X14H7B.

Thus, the use of a utility model, namely, a shaft, designed for strength in terms of endurance during torsion in a working fluid and yield strength in torsion using martensitic-austenitic steel with impact strength not lower than 7 kgm / cm ² as a shaft material and yield strength at

tensile testing up to 150 kGf / mm ² allows to increase the survivability of the shaft both under conditions of corrosion fatigue and under the action of pulsed more than 2.5-fold overloads.

Table 1 Chemical composition, wt.% Cr _eq Ni _eq Structure FROM Mn Si Cr Ni Cu Mo Ti Al With S R one 0.02 0.5 0.4 17.5 7.0 0.3 1,0 0.2 0.5 0.01 0.02 0,022 20.9 8.15 2,56 2 0,03 0.6 0.5 12.0 8.0 1.8 0.8 0.2 0.2 2.0 0.015 0.02 16.05 10.7 1,5 3 0.02 0.5 0.4 14.5 5,0 4,5 0.05 0.01 0.01 0.01 0.017 0.02 14.7 9.2 1,59 four 0.02 0.6 0.4 10.0 7.0 2,5 1.8 0.6 0.01 1,0 0.02 0.02 14.34 10.31 1.39 5 0.02 0.4 0.4 11.0 11.0 0.05 2.0 0.4 0.01 5,0 0.015 0,023 14.85 11.8 1.16 6 0.02 0.6 0.3 16.5 5,0 5,0 0.05 0.01 0.01 1,0 0.02 0.02 16.95 10.75 1,57 7 0,03 0.6 0.6 13.0 7.0 2.0 0.05 0.01 0.01 0.01 0,022 0,022 14.0 10,2 1.37 8 0.02 0.6 0.4 8.0 8.0 1,5 2,5 0.9 0.9 1,0 0.02 0.02 15.7 10,4 1.51 9 0.02 0.6 0.5 12.0 3.8 0.5 0.1 0.1 0.1 0.01 0.015 0,023 12.6 5.2 2.42 10 0.02 0.6 0.4 16,2 4.0 2.2 0.05 0.01 0.01 0.01 0.015 0.02 17.1 7.1 2,4 03X14H7V 0.02 0.6 0.4 13,2 6.1 - - - - - 0.017 0.02 14.1 6.9 2.04 table 2 Structure Strength, σ _in , kgf / mm ² Yield strength σ _t , kGf / mm2 Relates. elongation δ,% Relates. narrowing ψ,% Impact strength
KCU ₊₂₀ ; kgm / cm ² Torsional yield strength
τ _t , kgf / mm2 Torsion Corrosion Endurance
τ _-1 , kgf / mm ² one 120 105 9 35 6.5 68 25 2 137 130 10 52 8.0 91 40 3 125 115 12 65 12.0 72 32 four 135 130 10 fifty 8.0 90 38 5 155 150 10 fifty 7.0 105 fifty 6 95 80 13 60 15.0 fifty 32 7 130 125 10 58 8.0 88 37 8 170 165 5 25 3.0 110 twenty 9 110 90 12 58 7.0 56 25 10 125 117 12 54 6.5 75 28 03X14H7V one hundred 85 fourteen 58 15,5 52 24.5

Claims (2)

1. The shaft, mainly of a submersible pump, subjected to prolonged exposure to torsional and bending moments, including pulsed in nature, having recesses to accommodate connecting and fixing parts and splines at the ends, characterized in that its diameter, when calculated for strength, satisfies two maximum values permissible stresses, for which the torsion endurance limit with bending in the working fluid and the yield strength during torsion of the shaft material are selected, while the torque in the first case is corresponds to the steady state operation of the pump, in the second - not less than 2.5 times the magnitude of this torque, and the steel from which the shaft is made contains carbon, chromium, nickel, related impurities - manganese, silicon, sulfur, phosphorus and one or several elements from the group - copper, titanium, aluminum, molybdenum, cobalt in quantity, wt.%: FROM <0.03 Si <0.8 Mn <0.8 Cr 8.0-17.0 Ni 4.0-12.0 Cu 0.3-5.0 Mo 0.05-3.0 Ti 0.01-0.8 Al 0.01-0.8 Co 0.01-5.0 S <0.025 P <0.025 Fe rest and has a ratio of ferrite-forming and austenite-forming elements with their equivalence coefficients

; Ni _eq. = 22.3 ± 2.5-0.8 Cr _equiv. 2. The shaft, mainly of the submersible pump according to claim 1, characterized in that the steel from which it is made additionally contains one or more components from the group, wt.%: Nb 0.05-0.5 AT ≤0.005 N 0.005-0.2 Sa ≤0.01