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DE-102023121286-B4 - Device for the uniform nitriding of a steel ball batch and its method

DE102023121286B4DE 102023121286 B4DE102023121286 B4DE 102023121286B4DE-102023121286-B4

Abstract

Device for the uniform nitriding of a batch of steel balls, comprising a furnace body (1), an auxiliary heater (4), a tray (7), several movable thermocouples (8), a hollow shaft (9), a wireless transmitter (10), an upper cathode disk (11) and a lower cathode disk (12), wherein the furnace body (1) is a cylindrical vacuum chamber, the inner wall of the furnace body (1) is provided with a water-cooled wall, and a gas inlet opening (3) and a gas outlet opening (2) are provided on opposite sides of the furnace body (1), wherein the auxiliary heater (4) is arranged on the inner sides of the furnace body (1), the auxiliary heater (4) has a thermocouple for temperature monitoring, and heat shielding plates (5) are provided on the inner walls of the furnace body (1), wherein an upper cathode disk (11) and a lower cathode disk (12) are arranged in the uniform temperature zone in the furnace body (1), which are parallel The upper cathode disk (11) and the lower cathode disk (12) are supported and connected by support rods (13), the support rods (13) being conductors, and the upper cathode disk (11) and the lower cathode disk (12) are each provided with several gas holes, with several ceramic support feet (14) being provided between the lower cathode disk (12) and the bottom surface of the furnace body (1), a through-hole being provided in the center of the lower cathode disk (12), and the lower cathode disk (12) being connected to the negative electrode of the power source for the ion nitriding via an insertion electrode (15), with an inclined tray (7) being arranged between the upper cathode disk (11) and the lower cathode disk (12), the center of the lower surface of the tray (7) being connected to the hollow shaft (9), and the hollow shaft (9) passing through the through-hole into the center of the lower cathode disk (12) passes through and the lower end of the hollow shaft (9) protrudes from the furnace body (1), wherein the upper surface of the tray (7) is a conical surface, the center of the tray (7) is deeper than the outer ring, and several steel balls (6) are arranged in the tray (7), wherein several movable thermocouples (8) are embedded in the tray (7), the measuring ends of the movable thermocouples (8) in the The tray (7) is equidistant from the upper surface of the tray (7), and the lower ends of the movable thermocouples (8) are located in the hollow shaft (9), the wireless transmitter (10) being attached to the lower end of the hollow shaft (9) via a bracket, and the outputs of the movable thermocouples (8) being connected to the input of the wireless transmitter (10) via an aviation connector, the upper cathode disk (11), the lower cathode disk (12), and the support rods (13) forming a cathode system, the furnace body (1), the steel balls (6), the tray (7), and the hollow shaft (9) being connected to the positive electrode of the power source for the ion nitriding forming an anode system, and the furnace body (1) being grounded.

Inventors

  • Xinxin Ma

Assignees

  • HARBIN INSTITUTE OF TECHNOLOGY

Dates

Publication Date
20260513
Application Date
20230809
Priority Date
20230427

Claims (10)

  1. Device for the uniform nitriding of a batch of steel balls, comprising a furnace body (1), an auxiliary heater (4), a tray (7), several movable thermocouples (8), a hollow shaft (9), a wireless transmitter (10), an upper cathode disk (11) and a lower cathode disk (12), wherein the furnace body (1) is a cylindrical vacuum chamber, the inner wall of the furnace body (1) is provided with a water-cooled wall, and a gas inlet opening (3) and a gas outlet opening (2) are provided on opposite sides of the furnace body (1), wherein the auxiliary heater (4) is arranged on the inner sides of the furnace body (1), the auxiliary heater (4) has a thermocouple for temperature monitoring, and heat shielding plates (5) are provided on the inner walls of the furnace body (1), wherein an upper cathode disk (11) and a lower cathode disk (12) are arranged in the uniform temperature zone in the furnace body (1), which are parallel The upper cathode disk (11) and the lower cathode disk (12) are supported and connected by support rods (13), the support rods (13) being conductors, and the upper cathode disk (11) and the lower cathode disk (12) are each provided with several gas holes, with several ceramic support feet (14) being provided between the lower cathode disk (12) and the bottom surface of the furnace body (1), a through-hole being provided in the center of the lower cathode disk (12), and the lower cathode disk (12) being connected to the negative electrode of the power source for the ion nitriding via an insertion electrode (15), with an inclined tray (7) being arranged between the upper cathode disk (11) and the lower cathode disk (12), the center of the lower surface of the tray (7) being connected to the hollow shaft (9), and the hollow shaft (9) passing through the through-hole into the center of the lower cathode disk (12) passes through the center and the lower end of the hollow shaft (9) protrudes from the furnace body (1), the upper surface of the tray (7) being a conical surface, the center of the tray (7) being deeper than the outer ring, and several steel balls (6) being arranged in the tray (7), several movable thermocouples (8) being embedded in the tray (7), the measuring ends of the movable thermocouples (8) being equidistant from the upper surface of the tray (7), and the lower ends of the movable thermocouples (8) being located in the hollow shaft (9), the wireless transmitter (10) being attached to the lower end of the hollow shaft (9) via a bracket, and the outputs of the movable thermocouples (8) being connected to the input of the wireless transmitter (10) via an aviation connector, the upper cathode disk (11), the lower cathode disk (12), and the support rods (13) forming a cathode system forming the furnace body (1), the steel balls (6), the tray (7) and the hollow shaft (9) with which the positive electrode of the power source for the ion nitriding is connected and form an anode system, and the furnace body (1) is grounded.
  2. Device for the uniform nitriding of a steel ball batch according to Claim 1 , characterized in that the outer wall of the hollow shaft (9) and the furnace body (1) are sealed by a rotary sealing mechanism.
  3. Device for the uniform nitriding of a steel ball batch according to Claim 1 , characterized in that each movable thermocouple (8) in the tray (7) is connected to a wireless transmitter (10).
  4. Device for the uniform nitriding of a steel ball batch according to Claim 1 , characterized in that the lower end of the hollow shaft (9) is connected to a central drive shaft (16).
  5. Device for the uniform nitriding of a steel ball batch according to Claim 4 , characterized in that the central drive shaft (16) is connected to the power output shaft of the motor to achieve the rotation of the hollow shaft (9) and the tray (7).
  6. Device for the uniform nitriding of a steel ball batch according to Claim 1 , characterized in that the distance between the measuring ends of the movable thermocouples (8) and the upper surface of the tray (7) is 1-5 mm.
  7. Device for the uniform nitriding of a steel ball batch according to Claim 1 , characterized in that the aviation connector is arranged at the lower end of the hollow shaft (9) and a static seal is provided between the aviation connector and the hollow shaft (9).
  8. Device for the uniform nitriding of a steel ball batch according to Claim 1 , characterized in that the angle between the generating line of the conical surface of the tray (7) and the horizontal direction is 0.1-5°.
  9. Device for the uniform nitriding of a steel ball batch according to Claim 8 , characterized in that the lower surface of the tray (7) is a planar surface and forms an angle of 0-5° with the horizontal plane.
  10. Method for ion nitriding of steel balls using the device for uniform nitriding of a batch of steel balls according to Claim 1 , which is carried out with the following steps: 1. Loading of steel balls. The steel balls (6) are placed in the tray (7) until the distance between the outermost steel balls (6) and the inner edge of the tray (7) is 2 to 5 times the diameter of the steel balls (6); 2. The furnace body (1) is evacuated to a background vacuum; 3. The auxiliary heater (4) is switched on to raise the temperature in the furnace body (1) to a predetermined temperature; 4. Supply of nitriding gas; 5. After the pressure of the nitriding gas has stabilized, the power source for ion nitriding is switched on; the rotational speed of the hollow shaft (9) is set to 1-50 rpm and maintained for 1-10 minutes; The movable thermocouples (8) are rotated by the tray (7), causing the steel balls (6) to move towards the edge of the tray (7) under the influence of centrifugal force while simultaneously rotating circumferentially; then the rotational speed of the hollow shaft (9) is reduced to zero and held for 1-10 minutes; at the reduced speed, the steel balls (6) move towards the center of the tray (7) under the influence of friction and gravity; 6. Step (5) is repeated until the nitriding is complete; 7. the power source for the ion nitriding and the auxiliary heater (4) are switched off after the nitriding is complete; and the supply of nitriding gas is stopped and the hollow shaft (9) continues to rotate; and 8. after cooling, the hollow shaft (9) is stopped.

Description

Field of invention The invention relates to a device for the uniform nitriding of a batch of steel balls and its method. State of the art Nitriding is a typical process for increasing the surface hardness, surface wear resistance, and contact fatigue performance of steel parts. This process is particularly suitable for rolling contact components such as bearings and gears. After years of research, technologies such as gas nitriding and ion nitriding have been developed and applied to various parts. Compared to gas nitriding, ion nitriding offers a high nitriding rate and simple parameter control, and is already being used for bearing components. Bearing components have a complex structure, and when nitriding steel balls, in particular, it is crucial to obtain a uniform nitrided layer on the surface of the steel ball to ensure the bearing's service life and reliability. In ion nitriding, the workpiece, including the support structure, is generally nitrided as the cathode. Although technologies such as double nitriding by inverting the steel ball exist, which improves the uniformity of the nitrided layer to some extent, achieving a completely uniform nitriding effect remains impossible due to the effect of the cathode coating in ion nitriding and the directed incidence of ions. The main problem is that when using a steel ball as the cathode in ion nitriding, the sheath layers between the steel ball, the support element, and the tray overlap, creating a hollow cathode effect that leads to inconsistent surface temperatures of the steel ball. Although nitrogen ions moving in the direction of an electric field can improve uniformity, the nitrogen ion density of the plasma, with which each part of the ball's surface comes into contact, is not uniform. These two factors result in inconsistencies in the depth of the nitrided layer on the steel ball's surface. Even performing the ion nitriding process twice by inverting the steel ball does not fundamentally solve the problem of nitriding uniformity. Furthermore, the steel ball as a cathode occasionally generates an arc discharge, known as arcing, which causes localized burning on the surface, significantly impairing the surface quality of the steel ball and increasing the risk of bearing failure. Furthermore, in batch processing of steel balls, it is difficult to achieve uniformity of the temperature field throughout the nitriding furnace due to the influence of the uniformity of the discharge, which also affects the consistency of the nitriding of steel balls. DE 15 21 220 A , JP 2008-115 422 A , WO 2004/ 042 106 A1 , DE 10 2017 131 047 A1 and JP 2010 - 111 920 A This concerns devices for the nitriding of steel balls. Object of the invention To solve the problems of an uneven nitriding layer, surface burning caused by the arc discharge of steel balls in the ion nitriding process, and poor conformity of steel ball nitriding caused by an uneven temperature field in the existing ion nitriding process for the surface of steel balls, the invention provides a device for uniform nitriding of a batch of steel balls according to claim 1 and a method for its use according to claim 10. The device for uniform nitriding of a charge of steel balls according to the invention comprises a furnace body 1, an auxiliary heating device 4, a tray 7, several movable thermocouples 8, a hollow shaft 9, a wireless transmitter 10, an upper cathode disk 11 and a lower cathode disk 12. The furnace body 1 is a cylindrical vacuum chamber. The inner wall of the furnace body 1 is provided with a water-cooled wall. A gas inlet opening 3 and a gas outlet opening 2 are provided on opposite sides of the furnace body 1. The auxiliary heater 4 is arranged on the inner walls of the furnace body 1. The auxiliary heater 4 has a thermocouple for temperature monitoring. Heat shielding plates 5 are provided on the inner walls of the furnace body 1 to reduce heat loss in the furnace. In the uniform temperature zone in the furnace body 1, an upper cathode disk 11 and a lower cathode disk 12 are arranged parallel to each other. The upper cathode disk 11 and the lower cathode disk 12 are supported and connected by support rods 13. The support rods 13 are conductors. The upper cathode disk 11 and the lower cathode disk 12 are each provided with several gas holes for gas circulation. Between the lower cathode disk 12 and the bottom surface of the The furnace body 1 is provided with several ceramic support feet 14. The ceramic support feet 14 also have an insulating effect. A through-hole is provided in the center of the lower cathode disk 12. The lower cathode disk 12 is connected to the negative electrode of the power source for ion nitriding via an insertion electrode 15. An inclined tray 7 is arranged between the upper cathode disk 11 and the lower cathode disk 12. The center of the lower surface of the tray 7 is connected to the hollow shaft 9. The hollow shaft 9 passes through the through-hole in the center of