FR2498103A1 - PROCESS FOR WELDING REVOLUTION PIECES OF METALS OF VERY DIFFERENT HARDNESS AND MACHINE FOR PERFORMING SAID METHOD - Google Patents

Abstract

FRICTION WELDING PROCESS. IT CONSISTS OF TURNING A PART AND PRESSING ANOTHER PART AGAINST THE ONE WHICH IS TURNING AND, AFTER GENERATING THE DESIRED FRICTION HEAT, STOPPING THE SPINNING PART AND APPLYING A DISCHARGE AXIAL FORCE. BEFORE FRICTION WELDING, THE FRONT SURFACE OF THE ROTATING PART WHICH PRESENTS THE GREATEST HEAT RESISTANCE IS RAISED. WELDING INDUSTRIES.

Description

The present invention relates to a friction welding method of

  two parts having different heat resistance and made for example of steel and aluminum or light alloys, which consists of rotating one of the two parts which are tight, and pressing along the axis of rotation the another piece against the rotating one and, after having generated the desired heat of friction, to stop the rotating part and to apply to it a force

axial discharge.

  It has often been sought on a scientific basis

  that under what conditions one can weld together

  parts, for example steel and aluminum or its alloys.

  In this respect, it has been established, as far as

  to weld, that the welds, due to fragility, do not have sufficient mechanical strength. This fragility is attributed to the formation, in the weld zone, of intermetallic phases which are formed, at determined welding temperatures, by the softening and creep of the least resistant metal at the same time.

heat.

  As a result, testing was undertaken by the

  friction welding process which seemed, of course, to be

  because of the low welding temperature, but did not lead to any result that would be suitable for practical use. It was thought to find the cause in the

  formation of harmful intermediate layers, the composition of which

  their physical action have not been elucidated (the welding institute, June 1979

"Joining Aluminum To Steel").

  In practice, we turned to another way, starting from the principle of interposing between steel and aluminum an intermediate layer favoring welding

  by friction. The patent application submitted to the Inspectorate

  in the Federal Republic of Germany under the number

  2,606,628 describes the deposition of a tie layer containing

  silver on the non-aluminum part, this layer being subjected to a 1 to 2 hour heat treatment under gaseous protection to remove pores, bubbles and gaseous occlusions

  or others. After the recrystallization of the

  chage containing silver, we weld the two pieces by

  the known method of friction welding.

  In the patent application published in the Federal Republic of Germany under No. 2,752,584, a method is proposed for producing a reinforcement which is

  executed in two separate welding processes. In a field-

  first welding process, we obtain by welding by explo-

  on the part that is not aluminum an aluminum layer, which is used, in a second process of

  welding as an intermediate layer, to achieve the binding

its two parts.

  The two previous documents show, all

  research institutes, that it was not possible to

  according to the current state of the art, to achieve

  therefore, without using an intermediate layer, a solid bond, which can be used between metals

  having different heat resistance.

  The object of the invention is to enable welding

  direct friction of metal parts with resistance

  different heat currents, which meets the current requirements for mechanical strength,

  while avoiding the formation of intermediate layers.

  Surprisingly, the solution of this

  bleme is to set the front surface, intended for welding, of the rotating part, which has the greatest resistance to heat, after its tightening and immediately

before friction welding.

  By the use of the friction welding process in which no mixing of materials occurs,

  on the contrary, in which a clear separation of the

  the rate is maintained and which requires for welding a time

  lower than other welding processes,

  slows or prevents the formation of intermetallic phases

  c. But only if the front face of the part having the greatest heat resistance is erected immediately before friction welding can the mechanical strength of the weld be achieved which is desired in practice. In this regard, the fact that the part having the greatest heat resistance undergoes

  during training, a warming that favors the

  friction welding coming immediately thereafter, is also likely to play a role. This ensures, furthermore, on the one hand that the surface to be welded is exactly perpendicular to the axis of rotation of the friction welding machine, which causes uniform wear of the

  surface to be welded on the part with the lowest resistance

  heat, accompanied by a warm-up

  shape, which would not be ensured if the front surface of the part concerned was erected before tightening, because it would be created, when clamping the part, an angular gap between the surface to be welded and the axis of rotation

  that would make it virtually impossible to

  tion. On the other hand, the oxide skin preventing impeccable welding is removed in turn. A new oxide skin is created for a very short time, but it has a much smaller thickness and therefore has only a negligible influence on the quality

welding.

  During welding, while the part with the greatest heat resistance rotates, the end of the part having the lowest resistance to heat is plasticized due to the heat of friction and is thus pushed outwardly. , the very thin oxide layer formed after the dressing of the other piece being thus

driven out of the weld plane.

  The rotating part is then stopped, in the conventional manner, with the aid of a brake. At the same time, the heated and plastic material is forced outward by means of a larger axial displacement force. Both

parts are welded together.

  The beads that form during friction welding can be eliminated

  then with chip removal, by the technique

  known, using a tower mounted on the

friction welding machine.

  The invention thus provides the advantage of being able to

  mutually, in a correct manner in

  parts made of different metals, in particular steel and aluminum

  or light alloys whose shape is suitable for weld-

friction.

  The invention furthermore aims at a machine for welding by

  friction for carrying out the process according to the invention

  in which the lathe has a dressing tool guided in a radial plane along the frontal surface

  of the part driven in rotation.

  Friction welding machines of known type sometimes have turns. But these are intended for the lap removal of the weld bead after friction welding is completed and thus have

another goal.

  All forms of parts to which the friction welding process can be applied are suitable for

  process according to the invention. The invention does not exclude the use of

  also read parts that can be welded by friction,

  whose outer contour may not be considered absolute

  as revolution, but have a welding surface of revolution. Similarly, the invention applies not only to steel-aluminum welds, but also to

  those of other metals and their alloys having resistance

different heat levels.

Claims (2)

  1. A method of friction welding two pieces having different heat resistance and made for example of steel and aluminum or light alloys, which consists of rotating one of the two pieces that are tight, and to press along the axis of rotation the other piece   against the one that turns and, having generated the cha-   their desired friction, to stop the rotating piece   and to apply to it an axial force of repression,   characterized in that it consists in setting the front surface for welding the rotating part, which has the greatest resistance to heat, after its tightening and   immediately before friction welding.   2. Friction welding machine comprising a lathe   to carry out the process according to claim 1,   characterized in that the lathe has a dressing tool guided in a radial plane along the frontal surface of the part driven in rotation.