SU1507820A1 - Method of producing rolled strip of tool steels - Google Patents

Abstract

The invention relates to metallurgy and can be used in the production of hot rolled strip and sheet tool steel. The aim of the invention is to increase the yield due to obtaining a homogeneous structure of perlite 2-5 points with high quality surface strips. Steel 7HNM-ASHR is heated to 1200-1260 ° С and rolled on a 2300/1700 mill WPC-1 into a strip with a total reduction in the last two passes of 20-25% and a strip speed in the last pass of 5.0-7.5 t / s . The cooling rate during rolling in the range of 1200-1100 ° C is 0.8-2.0 degrees / s and 5-10 degrees / s in the temperature range 1050-700 ° C with an isothermal holding of 30-45 s at 1150-1000 ° C . The temperature of the end of rolling 700-850 ° C. At the end of the rolling, the strip is pressed for 3-5 seconds and further cooled by spraying on the discharge roller table, maintaining the zone of the top and bottom of the strip at a ratio of 1: (4-8). The cooling is carried out at a speed of 15–25 degrees / second until the rolled steel reaches a temperature of 500–700 ° C, after which the rolling of the rolled product is carried out. The invention provides guaranteed heating of the uniform structure of perlite 2-5 points with good quality of the rolled surface. 1 hp f-ly, 1 tab.

Description

The invention relates to metallurgy and can be used in the production of hot rolled strip and sheet tool steel.

The purpose of the invention is to increase the yield by obtaining a homogeneous structure of perlite 2-5 points with a high quality of the strip surface.

The invention is illustrated by the following example.

Example. Steel 7HNM-A1) 1P is heated to 1200-1260 ° C and rolled into a strip 1300/1700 LPTs-1 in a strip with a total compression in the last two aisles of 20-25% at a speed in the last pass of 5.0 - 7.5 m / s . The cooling rate during rolling is in the range. 1200-1100 ° С equal to 0.8-2.0 grg, p / s and

31507

5-10 degrees / s in the temperature range 1050-700 ° С with isothermal exposure 30-45 s at 1150-1000 ° С. The end of rolling temperature is 700-850 ° C. At the end of rolling, the subcontinent strip is within 3-5 s and is further cooled by spraying on the outgoing roller table, maintaining the length of the dividing zone at the top and bottom of the strip in the ratio of 1: (4-8). The cooling is carried out at a speed of 15-25 degrees / s until P1 reaches a temperature of 500-700 ° C by the dill, after which the rolling of the rolled stock is carried out.

When rolling on a mill 2300/1700 LPP-1 300 tons of hot-rolled strips with a section of 3.4-3.8 700-1050 mm from steel grade 7HNM-ASHR, the proposed conditions were implemented.

The results obtained during this rolling are shown in the table.

From the data presented in the table, it can be seen that compliance with the conditions set forth in the well-known solution (prototype) does not guarantee the homogeneous structure of perlite (experiment 3) and surface quality (experiment 2) o At. heating for rolling up to 1180 ° C and lowering the upper limit of the temperature range for rough rolling to 1180 ° C, subject to the conditions of the prototype, although it provides 2-5 grades of perlite, but the yield of the metal decreases due to the presence of roll imprints ( 2).

Experience 1 is the ideal case for obtaining perlite 2–5 and a fine surface. The absence of isothermal aging leads to obtaining differently grained perdite, 1–7 points, occluded / melted metal (experiment 3).

Thus, the signs in the well-known solution (prototype) do not cover the entire volume of the influencing factors, do not allow to consistently obtain the uniform structure of perlite and the quality of the surface.

With a total reduction in the last two passes within 20-25% due to the need to correct cuspidation, the shape of the strip and for other technological reasons, the reduction between these passages is redistributed, which contributes to obtaining in the last stand a critical degree of deformation causing intense grain growth. . In this case

Different-grained perlite is obtained, for example, 1-7 points (experiment 3).

Heating the metal under rolling to 1280 C (test 4) causes metal decarburization and perlite granularity of 1–6 points. Reducing the heating temperature to 1190 ° C (test 5) ensures a uniform perlite structure of 2-5, but the quality of rolled metal is unsatisfactory due to the presence of imprints from the rolls on the surface Heating for rolling up to 1200-1260 ° C: ensures the structure of perlite 2- 5 points good quality metal surface (experiments 6,7,8). Increasing the upper (experience 9) and lowering the lower (experience 10) temperature limits of rough rolling contributes to obtaining granulated perlite 1-6 points and reducing useful. The change in the temperature limits of the finish rolling also contributes to the same (experiments 13 and 14). At the same time, when carrying out rough rolling at 1200-1100 C and finishing - 1050-700 C, the metal has a uniform perlite structure of 2-5 points and a good surface (tests 6,7,8). A decrease in the cooling rate during rough rolling to 0.6 ° C (run 12) and to 4.0 ° C during finish rolling (run 15) leads to an increase in the granularity of pearlite to 1–5 bads. Increasing the cooling rate during rough rolling to 2.2 deg / s (experiment I) and 12 deg / s in finishing rolling (experiment 16) provides perlite 2–5 points, but the yield decreases due to the presence of roll imprints. At a cooling rate of 0.8-2 degrees / s at 1200-1100 ° C and 5-10 degrees / s at 1050-700 s, the metal has a uniform perlite structure of 2-5 points and a good surface quality (tests 6.7.8) .

Lowering the isothermal temperature to 980 C (test 17) results in perlite 1–3 points, deterioration of the surface, and increasing the temperature to 1170 ° C (test 18) contributes to obtaining different-grained perlite 1–7 points and embrittlement of the metal. The isothermal flow at 1150-1100 ° С for 30-45 s ensures the production of perlite 2-5 points and a metal with a good surface. Reduced duration

isothermal power supply up to 25 s. (experiment 19) to the embrittlement of the metal due to the production of heteromagnetic pearlite 1–6 points, and an increase to 50 s (experiment 2) also leads to the production of brittle metal.

When the cooling rate decreases before winding to 10.0 degrees / s (test 21), the metal becomes brittle due to the presence of differently grained perlite 2–7 points, and as the cooling rate increases to 30.0 degrees / s (test 22), local hardening takes place that also embrittles metal,

From the data in the table it can be seen that the proposed solution provides a homogeneous structure of perlite 2-5 points with good surface quality compared to the prototype, which allows to increase the yield by reducing the breaks and trimming of the ends of the bands and porosh during subsequent processing, as well as reduce the load on the equipment throughout the technological cycle.

Formula

6

goiter

p and e and

Claims (2)

1. A method for producing hot rolled strips of tool steels, including heating, hot rolling, cooling by spinning, and winding the strip into a roll at 700-500 ° C, characterized in that in order to achieve a suitable yield due to guaranteed obtaining a uniform perlite structure of 2-5 points with high quality of the strip surface, the steel is heated to 1200-1260 ° C, rolling is carried out with a cooling rate of 0.8-2.0 degrees / s in the interval of 1200 -POO and 5-10 degrees / s in the range of 1050-700 ° C with an isothermal charge for 30-45 s at 1150-1000 ° C, and cooling to coiling temperatures is carried out at a speed of 15-25 degrees / s. 2. A method according to claim 1, characterized in that the rolling is completed at 850-700 C.