SU1164281A1 - Method of heat treatment of weighted drilling pipes - Google Patents

Abstract

METHOD OF THERMAL TREATMENT OF ELASTICATED DRILL PIPES, including surface hardening and tempering of the middle part of the pipe,. volumetric hardening of the pipe ends after periodic induction heating up to 840-930 C and high tempering at 570630 ° C, characterized in that, in order to increase the wear resistance of the pipe, surface hardening and tempering of the middle part is carried out after volumetric hardening and high tempering of the pipe ends . . SL

Description

The invention relates to metallurgic rot and can be used in the heat treatment of extended drill pipes.

The purpose of the invention is to increase the wear resistance of the pipe.

FIG. 1-3 shows a flow chart of the method.

FIG. Figure 1 shows the principle of the emergence of the transition zone in the case of carrying out a volume heat treatment of the ends of the desired drill pipe after surface heat treatment. The area of existence of internal heat sources 1, arising in the metal under the influence of the electromagnet field of a periodic induction heater 2, is superimposed on the Hai zone of the preliminary surface heat treatment 3 being formed. close to the depth of penetration of the electromagnetic field into the metal. In 20-40 minutes, during which the end of the pipe is in a periodic heater, the metal is heated to 840-930 ° C in the volume of zone 4 due to thermal conductivity. The width of the transition zone increases to a value of t equal to 200250 mm. Throughout zone 6, the steel, previously heat-treated to a depth of T, equal to 5-7 mm, provides ;. with weakened. In connection with the fact that the pipe temperature in the transition zone of the temperature t reaches-values, at. in which the reverse structural transformations occur, the fine-needle martensite formed during surface hardening in a layer of depth V decomposes into a perlite-ferritic structure characteristic of a non-heat-treated metal.

Thus, when performing heat treatment of the untreated drill pipes in a manner known per se, the wear resistance of the entire lateral surface of the loose drill pipes with volumetric heat treatment of the ends is not achieved. During operation, upgraded drill pipes are rejected when the local surface is worn locally to a depth exceeding 3 mm. The presence of a pipe 2 transitional zones wide, the surface hardness ko; - close to

the hardness of the non-heat-treated source material negates the results of surface heat treatment of the middle part of the pipe as a whole. The service life of the pipe after carrying out heat treatment in this way does not increase.

FIG. 2 shows the absence of a transition zone when conducting a surface heat treatment of the middle part of the pipe after the bulk thermal strengthening of the ends. FIG. Figure 3 shows the section of the transition zone and the points at which the surface hardness was measured; line A shows the joining of the volume heat-treated tube end to the surface hardened average (tube end on the left).

The table shows the results of measurements of hardness in points, by two methods of heat treatment.

The method is carried out as follows.

Example. The pipe is fed alternately with each of its ends to the intermittent induction heater, where it happens, and the hardening and tempering at 840–930 ° C at 570–630 s. Zatgm mechanism moves the middle part of the pipe through a quenching inductor combined with a sprayer - the surface of the middle part of the pipe is heated to a depth of 5-7 mm to 890-930 C, followed by intensive cooling. Thereafter, the middle portion of the pipe is discharged.

With the proposed method, when volumetric hardening of the ends of pipes for cutting in these zones, a thread is obtained that is of equal strength along the entire length of the side surface, which leads to a significant increase in the wear resistance of the product as a whole. Carrying out the surface hardening of the middle part of the pipe after the operations of bulk quenching and tempering of the ends excludes the appearance of a transition zone with a reduced hardness value (see Fig. -2). The penetration depth of the electromagnetic field of the quenching inductor 1, combined with the sprayer, is equal to g, is 5-7 mm. The heating time of any point on the surface layer of metal 2 is 4-6 seconds, after which this point is intensively cooled. The value of S for the quenching inductor is 3-5 mm.

The expansion of this zone due to heat conduction does not occur due to the very high heating and cooling rates. After the surface hardening zone 2 comes into contact with the volume heat treatment zone 3 of the pipe end, the quenching inductor 1 is switched off. Surface hardening is over. However, the sprayer continues to work.

Points

Volumetric hardening of the pipe ends with the subsequent Surface hardening of the middle part (the proposed method).

315 310 312 307 380 520 525 528 530 525 538

164281.4

with continuous rotation and movement of the pipe until a zone of width P equal to 3-5 mm is cooled. Thus, this narrow strip 5 will receive the necessary hardness with full observance of the technology of surface hardening.

The economic effect of the introduction. This method is 305509 thousand 10 rubles.

Hardness on the HB scale

Surface hardening of the middle part of the pipe followed by the bulk hardening of the ends (known method)

303 315 300 308 310 315 210 225 220 230 250

YU

7 /

ipui.3

Claims (1)

METHOD FOR THERMAL TREATMENT OF LOADED DRILL PIPES, including surface hardening and tempering of the middle part of the pipe,. volume hardening of the pipe ends after periodic induction heating to 840-930 ° C and high tempering at 570630 ° C, characterized in that, in order to increase the wear resistance of the pipe, surface hardening and tempering of the middle part is carried out after volume hardening and high tempering of the pipe ends. . for heat treatment. - Electrical industry. Ser. Electrothermy, 1979, no. 8 (204). . USSR copyright certificate No. 850688, cl. C 21 D 1/12, 1981. figure 1> 1164281 2