FR2464107A1 - METHOD FOR STRETCHING PRODUCTS AND PRODUCTS PROCESSED THEREBY - Google Patents

Abstract

THE INVENTION CONCERNS THE TREATMENT OF METALS BY DEFORMATION. THE PROCESS WHICH IS THE SUBJECT OF THE INVENTION IS OF THE TYPE CONSISTING OF APPLYING TO THE PRODUCT TO BE STRETCHED 1 COUNTER-TENSIONING EFFORTS BY THE INTERMEDIATE OF A LUBRICANT 3 DOOR ON THE SURFACE OF THE PRODUCT, SUBMIT THE LUBRICANT DOOR ON THE SURFACE OF THE PRODUCT AT TIGHTENING ACCOMPANIED BY AN INCREASE IN PRESSURE IN THE LAYERS OF THE LUBRICANT TO A VALUE CORRESPONDING TO THE SHEAR STRESS VALUE OF THE LUBRICANT LAYERS, AND DEFORMATION OF THE PRODUCT, AND IS CHARACTERIZED IN THAT THE TOTAL VALUE OF THE COUNTER-TENSIONING EFFORTS REACHES 75 OF THE TOTAL STRETCHING EFFORT OF THE PRODUCTS. THE INVENTION APPLIES FOR EXAMPLE TO THE STRETCHING OF WIRES, RODS, TUBES.

Description

The present invention relates to methods of treating metals by

deformation and has especially for

  object a process for drawing products.

  The present invention is particularly applicable to the drawing of products of all types and all destinations (such as, for example, son, logs, tubes and others) on drawing benches

existing at present.

  Current developments in industrial production place increasingly stringent demands on the quality and reliability of the products obtained by drawing and, in addition, require a considerable increase in production by intensifying the process of stretching through the production process. increase in drawing speeds and

  also unitary and total deformations.

  At the present time, the drawing of the products is still mainly in the limit friction regime, which means that the surfaces of the product and the tool are directly in contact. Even with a satisfactory lubricant, one has to spend 30% to 50% of the effort

  total draw to overcome external friction.

  High labor costs and low productivity

  of the work that characterizes the old technology

are well known.

  The distribution of the residual stresses in the drawn metal intended to be used in the hardened state (for example in the targets) or to undergo a subsequent plastic deformation is optimal when residual stresses of compression are present in the layers

superficial products.

  The known methods of drawing products cause the appearance in the superficial layers

  high tensile stresses, the importance of which

  tance is sometimes commensurable with the strength properties of the metal, leading to the destruction of the products during drawing or still in service or

during their storage.

  A product drawing process is known (see, for example, U.S. Patent No. 3163285 of Dec. 29, 1964) by applying counter-tensioning forces when applying lubricant to the surface of products, clamping the lubricant on the product surface with simultaneous increase in pressure in the surface layers of said lubricant to a value corresponding to the shear stress value of the lubricant layers, and deformation

of the product.

  In this process, the deformation of the product is done in an elongated zone and the residual stresses

  are eliminated by a small reduction of the order of 3%.

  However, the large deformation zone that is formed when using this method does not allow the drawing of products with significant deformations

  unit and total and high draw speeds.

  Moreover, in this method, the value of the counter-tension forces (which does not exceed 40% of the effort

  drawing) does not allow to obtain residual constraints

  dual compression in the surface layers of the product, which makes it impossible to perform the drawing

  with significant unitary and total deformations.

  It has therefore been proposed to create a product drawing process in which the total value of the counter-tensioning forces would be such as to reduce the residual tensile stresses in the surface layers of the product and to obtain

  residual compression stresses.

  This problem is solved by the fact that the method of drawing products of the type consisting in applying counter-tensioning forces when applying a lubricant to the surface of the product with simultaneous increase of the pressure in the surface layers of said lubricant to a value corresponding to the value of the shear stress of the lubricant layers, and of the deformation of the product, is characterized, according to the invention, in that the total value of the counter-tension force is equal to 75% of the total effort

drawing of products.

  It is desirable that efforts to counter

  tension are applied in incremental increments of values as one approaches the

deformation.

  It is advantageous that a total value of counter-tensioning forces of up to 65% of the drawing force is achieved by counterpressure of the lubricant layers on the product surface prior to deformation. It is preferable that a total value of up to 75% contraction stresses of the drawing force is obtained by a reduction of the product as a result of the back pressure of the lubricant layers.

on its surface.

  The invention makes it possible to adjust the counter-tensioning forces and to obtain, throughout the stretching process, an optimum distribution of the counter-tensioning forces, reducing the total drawing effort and

  allowing drawing at high speeds.

  The invention also ensures a significant reduction in the level of the tensile stresses and the appearance of compression stresses in the surface layers of the products, which makes it possible to increase the

  total deformations while improving the characteristics

  physical and mechanical ticks of the products obtained.

  The invention will be better understood and other purposes, details and advantages thereof will appear better in the

  light of the explanatory description which will follow from

  various embodiments given solely by way of nonlimiting examples, with reference to the drawings

  non-limiting conditions in which:

  FIG. 1 represents a longitudinal sectional view

  dinal of a product drawing device for carrying out the stretching method with two steps of application of the counter-tensioning forces by the counter pressure of the lubricant, according to the invention; - Figure 2 shows a longitudinal sectional view of a product drawing device for carrying out the drawing method with three steps of application of counter-tensioning forces, according to the invention; FIG. 3 shows the distribution pattern of the lubricant back pressure and the counter-tension forces in the device of FIG. 1, according to the invention; FIG. 4 shows the distribution pattern of the lubricant back pressure and the counter-tension forces in the device of FIG. 2, according to the invention; FIG. 5 represents the distribution pattern of the residual stresses according to the section of the product in the case of application of the counter-tensioning forces in

three steps, according to the invention.

  The process of drawing products consists only of

  that at the same time as the application of

  tension reaching 75% of the drawing force, applying a lubricant on the surface of the product, then tightening the lubricant on the surface of the product with simultaneous increase in pressure

  in the lubricant layers to a corresponding value

  spanning shear stress value in the lubricant layers, the deformation

of the product.

  According to this method, in order to reduce the drawing force and to ensure the drawing of the products at high speeds, the counter-tensioning forces are applied in increments of increasing successive values as

  we are getting closer to the focus of deformation.

  A total value of the counter-tensioning forces up to 65% of the drawing force is obtained under the action of the lubricant backpressure on the

  product surface before deformation.

  A total value of the counter-tensioning forces of up to 75% of the drawing force is achieved by subjecting the product to a reduction as a result of the counter-pressure of the lubricant on its surface. The product drawing method according to the invention can be used on any known type of drawing device operating in hydrodynamic friction regime. One of the known variants of the product drawing device comprises, in the direction of displacement of the product 1, constituted in this case by way of example by a wire (FIG. 1): a chamber 2

  for the application of the lubricant 3, in which

  kills the adsorption by the wire 1 of a layer 4 of lubricant 3, a pressure tube 5 in which the layer 4 of

  lubricant 3 is tightened to a corresponding value

  laying down at the shear stress value of the layer 4, a lubricant pressure stabilizer 6 (as a stabilizer a locking ring 6 is used), in which the layer 4 is tightened to a pressure exceeding the limit The working die 'i' locking ring 6 and the pressure tube 5 are fixed in a housing 8 by means of a conical bush of

  tightening 9 and a tightening nut 10.

  The first echelon of counter-tension forces is created by the pressure tube 5, and the second echelon

by the ring 6.

  In another known device (FIG. 2), a reduction die is placed between the die of

Work 7 and Ring 6.

  The first and second echelons of counter-tensioning forces are obtained as in the device shown in FIG. 1, the third echelon being

  created by the reduction channel 11.

  The product drawing device, when carrying out the stretching process with two steps for applying the counter-tension forces according to

  to the invention operates as follows.

  The lubricant 3 (FIG. 1) applied to the surface of the wire 1 is clamped in the pressure tube 5 to a value corresponding to the shear stress value of the layer 4 of the lubricant 3, thus giving rise to a pressure PI (shown in Figure 3) which provides a counter-tension force H1 (shown in Figure 3) whose value does not exceed% of the drawing or drawing effort. As the thread advances, the lubricant thus tightened passes through the locking ring 6 (FIG. 1) which pockets the layer 4 of the lubricant 3 to move in the opposite direction; so that the tightening of the layer 4 of lubricant 3 reaches a pressure P2 (shown in FIG. 3) greater than the elastic limit of the material of the wire 1 (FIG. 1). The pressures P1 and P2 (FIG. 3) provide a counter-tension force H2 (FIG. 3) that reaches 65% of the drawing force. This value H2 (FIG. 3) of the counter-tension force applied to the surface layers of the material of the wire 1 (FIG. 1) gives rise to a displacement in the opposite direction of these layers, which, together with the subsequent deformation in the working channel 7, ensures the removal of residual tensile stresses and the appearance of low residual compressive stresses in the layers

  surface of the wire material 1.

  The product drawing device, when carrying out the drawing process with three steps of application of the counter-tension forces according to

  The present invention operates as follows.

  After having passed through the locking ring 6 (FIG. 1, 2), the wire arrives in the reduction die 11 which creates an additional counter-tension. For the rest, the operation of the device is similar to that of the device described above. In this case, the total value H3 of the counter-tensioning forces (FIG. 4) reaches 75% of the drawing effort. Consequently, in the surface layers of the material of the wire 1, major compressive stresses 6, shown in FIG. 5, emerge. The invention makes it possible to avoid cracking during wire drawing of steel wires with hardening and hard deformation. , to increase the resistance to fatigue of the yarn and to increase the service life of the

  products made from this thread.

  Table 1 below shows the results obtained using various variants of application of the counter-tensioning forces. It emerges that when the counter-tensioning forces are applied in incremental increments of successive values, it is possible to ensure

  a stable stretching process with counter efforts

  the total value of which reaches up to 75% of the drawing effort, thanks to a reduction

  prior to the effort of stretching

  applied to the first step. At the same time, it is possible to obtain high compressive stresses which make it possible to stretch with large total deformations and high drawing speeds and to substantially increase the plastic properties of the material.

  metal while retaining its strength properties.

  Table 2 below shows the wire drawing parameters of steels and alloys of different grades according to the process according to the invention. The drawing speed is then 10 to 25 m / s, the unit strain is equal to 30 - 45%, and the total strain between heat treatments reaches 75 to 95%. The tenacity of the drawing tool

increases several times.

Table 1

  Counter-tension Stresses Process in% with respect to Stretching residual stretching forces at the drawing effort superficial drawing% total steps of

f 96 trac-

% tion sion

1 2 3 4 5 6 7

Process - 5 5 88 98 -

drawing - 10 10 82 55 -

of products - 20 20 100 45 -

- 30 30 110 35 -

- 40 40 125 25 -

- 45 45 160 20 -

20 35 93 30 -

30 45 100 20 -

40 55 109 5 -

50 65 118 - 10

60 75 124 - 48

70 85 163 - 70

  Table 1 (cont.) Limit Deformation Between Consumption Annealed characteristics up to tools of the product drawing destruction process,

8 9 10

20 stable

20 - "

15 - "-

10 - "-

10 - "

  no data no data many breaks 20 stable

18 - "-

18 - "

250 15 - "

300 15 - -

  no data no data many ruptures

Table 2

  N Thread Material Speed of Distortion Reductions

  wire drawing unit total amount m / s%

1 2 3 4 5

1. Low carbon steel

bone (C to

0.3%) 18-20 45 95

  2. Medium carbon and high carbon steel 10 30 90 3. Steels and alloys (heat resistant, nickel-chromium) 12-15 35-40 75 4. High alloys

resistance

with crack

ration (chrome-

nickel, nickel

molybdenum) 10 30 75

5. Bimetal (steel-

aluminum and steel-copper) 10 30 85

6. Mechanized rolled wire

  10-15 30-40 90 7. Non-ferrous metals and their alloys 10-15 30-40 90 Table 2 (continued) Decrease in Increase Decrease Increase

  consumption of the tenacity of the coef-

  of energy of the tool ficients electrical conductivity of labor work of the% metal%%

6 7 8 9

  -20 -7 -15 0.2 0.4 max -15 no data no data no data no data 30 no data 1.0 no data 4-6 Of course, the invention is in no way limited to described and illustrated embodiments which have been given by way of example only. In particular, it includes all the means constituting technical equivalents of the means described as well as their combinations if they are executed according to its spirit and implemented.

  in the context of protection as claimed.

Claims (5)

R E V E N D I C A T I 0 N S   1. A method of drawing products, of the type consisting in applying to the product to stretch counter-tensioning forces via a lubricant carried on the surface of the product, to subject the lubricant carried on the surface of the product at a clamping being accompanied by an increase in the pressure in the layers of said lubricant to a value corresponding to the value of shear stress of the lubricant layers, and a deformation of the product, characterized in that the value total counter-tension effort reaches 75%   the total effort of drawing products.   2. A process according to claim 1, characterized in that the counter-tensioning forces are applied in steps of increasing successive values to measure   that we are getting closer to the focus of deformation.   3. Method according to one of claims 1 and 2,   characterized in that a total value of the counter-tensioning forces of up to 65% of the drawing force is obtained under the action of the back pressure of the lubricant layers on the surface of the product before it deforms .   4.- Method according to one of claims 1, 2   and 3, characterized in that a total value of the contractive stresses of up to 75% of the drawing effort is obtained by a reduction of the product as a result of   said backpressure of the lubricant on its surface.   5.- Products characterized in that they have been stretched in accordance with the process which is the subject of one of claims 1 to 4.