SU765375A1 - Method of dead steel rolling stock treatment for cold upsetting - Google Patents

Description

The invention relates to the field of ferrous metallurgy, in particular, to rolling production and heat treatment of steels for cold heading. Known methods of processing steel for cold heading, ensuring their deformability during cold draft, these methods include accelerated cooling of steels from rolling heating to various (820-680 ° C) temperatures, in some cases intermediate heat treatment, cold plastic deformation (drawing, calibration) with various degrees of reduction, subsequent heat treatment in various modes. There is also known a method of treating rolled products from medium carbon steel for cold heading, including the accelerated cooling to 700-400 s and then in air. Ca. vibration and single-stage annealing at AC 3. The disadvantage of this method is that the steel withstands sludge up to 1/3 of its original height after treatment. The closest to the proposed technical essence and the achieved result is the method of production of wire for cold heading, which includes accelerated cooling from rolling heating to a temperature of 820-780 ° C with a speed greater than the critical one, for example 300350 C / s, air cooling, drawing, heating to temperatures of the first stage of annealing for 3 hours, first stage of annealing at 760-780 ° C for 2 hours, cooling to 500 ° C in 0.5 hours, heating to a temperature of the second stage of annealing for 0.5 hours, second stage of annealing at 660-680 ° C for 3-5 hours, cooling with a furnace up to 80 ° С 4. The disadvantage of this method is that after annealing, the steel exhibits low deformability during cold heading and therefore does not guarantee the required cold draft up to 1/3 of the original height in the process samples. The aim of the invention is to increase the rolling deformability of

calm medium carbon steels with cold sediment.

This is achieved by the fact that the first stage of annealing is carried out at 800–820 ° C for 1–1.5 h, followed by cooling at a rate of 100,120 cps / min to 300 ° C, and the second stage at an As. temperature, followed by air cooling.

The essence of the method is as follows.

Calm carbon steel is rapidly cooled from rolling heating to a temperature of 820-780 ° C at a speed of 300-350 ° C / s, cooled in air, dragged (calibrated), heated to a temperature of the first annealing stage at a speed of 20-25 C / min, annealed in the first stage at 800–820 ° C for 1–1.5 h, cooled at a speed of 100–120 deg / kmn, heated to the temperature of the second stage of annealing at a speed of 20 .25 C / min, annealed in the second stage at an AC temperature. within 3-5 hours and cooled in air.

A higher temperature of the first stage of annealing (800–820 ° C) allows spheroidizing the sulfide eutectic observed in calm medium carbon steel for 1–1.5 h, which provides an improvement in the deformability of the steel during cold landing.

At temperatures below 800 ° C, spheroidization of sulfide eutectics slows down dramatically, with the result that very long exposures are necessary, which adversely affects the size of the austenitic grain, and hence also. on the deformability of steel in a cold state. Exposure steel at

these temperatures for 1-1.5 hours or less does not ensure the spheridization of sulfide eutectics.

At temperatures higher already with minimal time exposures. Along with spheroidization, the process of coalescence of sulphide eutectic is intensively proceeding, which leads to embrittlement of steel during cold sediment.

Cooling after steel

 the annealing stage to a temperature at a rate of 100-120 s / min is due to the need to obtain austenite decomposition products in the intermediate region, which later on

5 of the second stage of annealing facilitates the formation of homogeneous austenite, or spheroidization and coalescence of cementite.

The second stage of annealing at a critical temperature AU contributes to the formation of a more equilibrium structure of the steel, ensuring their increased deformability during cold heading.

5 Air cooling allows to reduce the debt of the thermal equipment.

Processing method tested on steel Art. 35 selets with a diameter of 16 mm produced by the Krivorozhstal plant

Experienced processed according to various versions of the proposed method, technological samples of steel Art. 35 selects for upsetting in a cold state to 1/3, 1/4, 1/5, 1/6 of the original height.

The results of the test of five samples are shown in the table.

Weathered Not held out I could not stand sting The Same Weathered || The same Vzhederzhshi endured the Same Weathered

4 5 3 4 5 3 4 5 3

1.5

1.5

0.5

four

5 In all cases, the steel is subjected to accelerated cooling from rolling heating to a temperature of 820-780 s at a speed of 300-350 C / s / cooled in air, dragged, heated to the temperature of the first stage of annealing at a speed of 20-25 ° C / min, cooled to a temperature of 100–120 C / min, heated to a temperature of the second stage of annealing at a rate of 20–25 C / min, and cooled in air. For comparison, steel St 35 select, tested by a known method, was tested. At the same time, steel dragged accelerated from rolling heating is heated to a temperature of the first stage of annealing for 3 hours, maintained at 770 ° C of the first stage of annealing for 2 hours, cooled to 0.5 hours, heated to a temperature of the second annealing for 0.5 h, maintained at the second stage of annealing for 4 h and cooled with a furnace to. As a result, with a cold draft, up to 1/3 of the original height of the 10 tested samples 3 did not overload the draft. In tests of 10 samples on the draft up to 1/4 of the original height, no sample withstood the sample.

Table continuation

II n

 -

and 11

II „and

ti and II n If ti ii

He stood- He stood He didn’t hold

The same

The same

Similarly, II II Vzderzhali From the above data it can be seen that the proposed method of processing quiet medium-carbon steels for cold heading increases their cold deformability from 1/3 of the initial height to 1 / 5-1 / 6. High deformability will reduce the number of defects in the manufacture of hardware products, get JJt method of cold heading calm medium carbon steel, approximately 16-18%. Formula of the invention. A method for processing cold steel steels for cold heading is mainly medium carbon, including cooling from rolling heat up to 820-780 s at a speed greater than critical, then in air, calibration and two-stage annealing with an exposure at the second stage of 3-5 hours, differing in that, in order to increase the deformability of steels during cold settling, the first stage of annealing is performed at 800-82 ° C for 1-1.5 hours, followed by cooling at a rate of 100-120 ° C / min to 300 ° C, and second stage - at temperatures Aj, followed by cooling in air. Sources of information taken into account in the examination,.,. 1. Steel, 1976, 8, p. 750-754.- 2. Sheftel n.I. Production of steel calibrated bars M., Metallurgi, 1970, p. 27-29. 3. Sat. Heat treatment of metals No. 5, M., Metg1Lurgists 1977, p. 44-47. . 4. TU 14-4-711-76.

Claims (1)

Claim A method of processing rolled steel from mild steels for cold heading of predominantly medium-carbon steels, including cooling from rolling heating to 820-780 ° C at a speed greater than critical, then in air, calibration and two-stage annealing with an exposure time of 3-5 hours in the second stage, characterized in that , in order to increase the deformability of steels during cold precipitation, the first stage of annealing is carried out at 800-820 ° C for 1-1.5 hours, followed by cooling at a speed of 100-120 ° C / min to 300 ° C, and the second stage - at temperature A _{fct |} followed by cooling in air.