RU2047469C1 - Method of working article by surface plastic deformation method - Google Patents

Abstract

FIELD: plastic metal working. SUBSTANCE: during process of working, additional twisting stresses are applied to material worked. Directions of the stresses are opposite to direction of tangential component of spinning force. As a result, temperature decreases at deformation area. EFFECT: improved wear resistance; increased fatigue strength. 2 dwg, 1 tbl

Description

 The invention relates to mechanical engineering, mainly to processes for finishing surfaces of machine parts.

A known method of processing parts by surface plastic deformation, in which the workpiece is reported to rotate, and the deforming tool is pressed against the surface to be treated with a certain force, giving it a longitudinal feed [1]
A disadvantage of the known method of processing a part by surface plastic deformation is the low quality of the treated surface, which is expressed in the uneven distribution of the physicomechanical properties of the material of the surface layer and its inhomogeneous microrelief.

A known method of hardening parts by surface plastic deformation, in which the tool is informed by ultrasonic vibrations with a varying amplitude and moves it to an equidistant machined surface, and the part is rotated with the formation of a regular microrelief on it, and the amplitude of the ultrasonic vibrations is changed stepwise depending on the required parameter of the microrelief, the dimensions of the part and angular velocity of its rotation [2]
A disadvantage of the known method of hardening parts by surface plastic deformation is the low tool life at high energy intensity of the processing process.

A known method of processing surface plastic deformation, in which the parts indicate rotation, and the cylindrical tool is pressed against the work surface with a constant deformation force and swing it around the axis normal to the surface to be machined through the center of the contact spot of the tool with the part, to form a regular relief in the form of inclined grooves, the cylindrical tool is rotated towards the grooves, and the rotation angle is selected greater than the maximum the angle of swinging the tool in the opposite direction [3]
The specified method of processing parts by surface plastic deformation is taken as a prototype.

 A disadvantage of the known method of processing a part by surface plastic deformation is the low efficiency of the process, which is expressed by the low processing productivity and low tool life due to its rotation and forced swaying during plastic deformation of the metal.

 The objective of the invention is to increase the efficiency of the method of processing parts by surface plastic deformation.

e^0,1ν·Kρ K
где σ_m предел текучести обрабатываемого материала, кг/мм²;
R приведенный радиус кривизны контактирующих поверхностей, мм;
ΔН толщина упрочненного слоя поверхности обработанной детали, мм;
ν коэффициент Пуассона;
K_ρ показатель дислокационной насыщенности обрабатываемого материала, равный отношению текущего значения плотности дислокаций материала ρ, полученной на предыдущей операции, к ее исходному значению ρ_исх.To achieve a technical result in the surface layer of the shaft during the running in the direction opposite to the tangential component of the rolling force, torsion stresses are created, the maximum value of which is determined by the formula
τ _max = (0.35.0.60)

e ^{0,1ν · Kρ} K
where σ _{m the} yield strength of the processed material, kg / mm ² ;
R is the reduced radius of curvature of the contacting surfaces, mm;
ΔН thickness of the hardened layer of the surface of the machined part, mm;
ν Poisson's ratio;
K _{ρ is the} indicator of the dislocation saturation of the processed material, which is equal to the ratio of the current value of the density of material dislocations ρ obtained in the previous operation to its initial value ρ _ref .

K _ρ ρ / ρ _ref . To the coefficient of compactness of the unit cell of the crystal lattice of the processed material;
D diameter of the workpiece, mm.

 The essence of the method lies in the fact that additional torsional stresses are created in the processed material during the surface plastic deformation, the direction of which is opposite to the direction of the emerging tangential component of the break-in force. The generated torsional stresses reduce the tangential component of the break-in force, as a result of which the temperature in the zone of plastic deformations decreases, since the heat of deformation during finishing and hardening of parts is proportional to the tangential force (p. 18). Friction strain loss is reduced; there is a redistribution of the dislocation of the crystal lattice of the metal, leading to an increase in the statistical uniformity of the quality indicators of the surface layer of the machined part. The height of the roughness of the treated surface is reduced. As a result, the wear resistance and fatigue strength of metals and the resistance of the hardening tool are increased.

The generated torsional stresses should not cause an avalanche formation and dislocation movement along the slip planes in the processed material, which would lead to a sharp increase in the tangential component of the break-in force and a decrease in the effectiveness of finishing hardening. Therefore, the value of the maximum torsional stresses generated in the material to be processed should be assigned taking into account the type of crystal lattice of the material, characterized by the compactness coefficient of the unit cell, the state of the dislocation structure of the material obtained in the previous machining operation and expressed through the dislocation saturation index of the processed material K _ρ equal to the ratio of the current density value dislocation ρ to its initial value ρ _out. K _ρ ρ / ρ _out . as well as the dislocation mobility, which for torsion is determined by the exponential dependence e ^{0.1 ν K} ρ and is due to the energy of elastic distortions of the dislocation core, where ν is the Poisson's ratio.

где М_кр прикладываемый к обрабатываемой детали дополнительный крутящий момент;
W_р полярный момент сопротивления; для сплошного сечения обрабатываемого вала диаметром D W_p ≈ 0,2D³;
Максимальная величина прикладываемого к обрабатываемому валу крутящего момента М_кр равна
M_кр= P_т·

где Р_т тангенциальная составляющая силы откатки;
Р_т/Р_н 0,07-0,12, где Р_н нормальная составляющая силы обкатки (I, с. 12-13).The maximum value of torsion stresses in the cross section of a cylindrical part is determined by the formula
τ _max =

where M _cr applied to the workpiece additional torque;
W _{p the} polar moment of resistance; for a solid section of the machined shaft with a diameter of DW _p ≈ 0.2D ³ ;
The maximum value of the torque M _cr applied to the work shaft is equal to
M _cr = P _t

where P _{t the} tangential component of the force of the rollback;
P _t / P _n 0.07-0.12, where P _{n is the} normal component of the break-in force (I, p. 12-13).

But R _n 2 σ _m (1 + 0,07R) ² ˙ ΔH ² , where σ _{m the} yield strength of the processed material;
R is the reduced radius of curvature of the contacting surfaces;
Δ N the thickness of the hardened layer of the machined surface of the part (I, p. 48).

e^0,1ν·Kρ ·K
Практическое осуществление способа обработки детали поверхностным пластическим деформированием сводится к закреплению детали в приспособлении (например, трехкулачковом патроне передней бабки токарного станка); создании при помощи дополнительного устройства в обрабатываемом материале напряжения кручения (например, в результате создания крутящего момента на противоположном конце обрабатываемого вала, закрепленном в трехкулачковом патроне специального устройства, установленном на месте задней бабки токарного станка); подводе к обрабатываемому валу отделочно-упрочняющего инструмента; создании необходимого усилия деформирования, обусловленного требуемой толщиной упрочненного слоя ΔН; включении на станке вращения детали и движения продольной подачи инструмента.Then the maximum value of the torque M _cr applied to the work shaft is equal to
M _cr (0.07-0.12) σ _m (1 + 0.07R) ² ˙ Δ H ² ˙ D, and the maximum value of torsion stresses in the cross section of the part, taking into account the characteristics of the crystalline structure of the material, is determined by the formula
τ _max = (0.35.0.60)

e ^{0,1ν · Kρ} · K
The practical implementation of the method of processing a part by surface plastic deformation reduces to fixing the part in a fixture (for example, a three-jaw chuck of the front headstock of a lathe); creation by means of an additional device in the processed material of torsion stress (for example, as a result of creating a torque on the opposite end of the processed shaft, fixed in a three-jaw chuck of a special device installed in place of the tailstock of the lathe); supply to the machined shaft of the finishing-strengthening tool; creating the necessary deformation force due to the required thickness of the hardened layer ΔН; turning on the machine rotation of the part and the movement of the longitudinal feed of the tool.

 Figure 1 presents a diagram of the practical implementation of the method of processing the part by surface plastic deformation, where 1 workpiece, 2 tool, 3 chuck of the front headstock of the machine, 4 chuck of the back headstock of the machine, 5 tailstock, in which the device for creating torsional stress in the material being placed . Figure 2 shows a schematic diagram of a device for creating torsion stress in the material being processed, where 1 pulley, 2 brake belt, 3 spring, 4 tension rotary washer, 5 support cup, 6 measuring scale.

For comparison, the processing of batches of parts by surface plastic deformation in two ways according to the prototype and the proposed method. Rolls made of steel 20XH (σ _m 65 kg / mm ² ) with a length of 480 mm and a diameter of 40 mm were subjected to surface plastic deformation, which were installed and fixed on a screw-cutting machine of modes. 1I611P having a device for generating torsion stress in the processed material. Previously, the rollers were subjected to grinding on a circular grinding machine mod. 3A151, with the result that the average dislocation saturation index was K _ρ 120. As a tool, we used a roller runner from a hardened high-speed stage Р6М5 with a diameter of 48 mm and a radius of the working profile of R 12 mm. The deformation force was 1.5 kN, which should provide a thickness of the hardened layer of the machined surface of the part ΔN of 0.6 mm. The conditions of surface plastic deformation of the prototype: the amplitude of the wiggle of the tool is 5.6 mm; tool rotation angle of 10 ^about . The condition of surface plastic deformation by the proposed method; τ _max 0.35 kg / mm ² 3.5 MPa, which was achieved by creating a braking torque of 4.48 kg ˙ m in the device located in the tailstock of the lathe.

 The obtained average values of the performance indicators of the methods of processing parts by surface plastic deformation according to the prototype and the proposed are shown in the table. An analysis of the data presented shows that the proposed method for processing a part by surface plastic deformation of a metal allows 1.2–1.3 times higher processing productivity, 1.5–1.8 times higher tool life, 15–20% better uniformity the quality of the machined surface of the part.

Claims (1)

METHOD OF PROCESSING DETAILS BY SURFACE PLASTIC DEFORMATION, including the deforming effect of the reinforcing tool on the machined surface of a rotating cylindrical part, characterized in that in the surface layer of the machined part in the process in the direction opposite to the tangential component of the rolling force, torsional stresses are created that are equal to the maximum value
τ _max = (0.35 ... 0.60)

where G _{m the} yield strength of the processed material, kg / mm ² ;
R is the reduced radius of curvature of the contacting surfaces, mm;
ΔH thickness of the hardened layer of the surface of the part, mm ν Poisson's ratio,
Kρ is the indicator of the dislocation saturation of the processed material, equal to the ratio of the current value of the material dislocation density r obtained in the previous operation to its initial value ρ _ref .
Kρ = ρ / ρ _ref ;
K is the coefficient of compactness of the unit cell of the crystal lattice of the processed material;
D diameter of the workpiece, mm.

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