SU1305183A1 - Method for manufacturing large-sized sheets,particularly from austenitic corrosion-resistant steels - Google Patents

Abstract

The invention relates to the field of ferrous metallurgy and can be used in the manufacture of sheets with high strength properties and high flatness. The purpose of the invention is to improve the quality of sheets by increasing the strength properties of steel and flatness of sheets. After the etching operation, the sheets are rolled in a cold state for a strain of 20-60%, which leads to a high level of strength properties of the steel. After rolling, the sheets are assembled into packages with flat support plates placed between them and the two-stage tempering is carried out in a hard-boiled state: first at 150-250 ° C for 1-3 hours and then at 350-450 ° C for 2-6 hours. Two-stage tempering is carried out to further increase the strength properties of steel and flatness of the sheets. Heating up to 350-450 C leads to the release of -carbides in deformation martensite, which provides the optimal combination of strength and plastic properties of steel. 1 tab. w (L With so about ate EO 00

Description

one . 13

The invention relates to ferrous metallurgy, in particular, to the production of large-size sheets of austenitic corrosion-resistant steels with improved strength properties and high flatness of the sheets.

The purpose of the invention is to improve the quality of sheets by increasing the strength properties of steel and flatness of sheets.

The essence of the invention is that after the etching operation, the sheets are rolled in a cold state with a reduction of 20-60%, and then they are collected in bags and two-stage tempering is carried out in the under-supported state between flat base plates. The first stage is carried out at 150-250 C for 1-3 h, and the second - at 350-450 C for 2-6 h.

Cold rolling is carried out with a reduction of 20-60% to obtain a high level of strength properties of steel. Compression to 20% does not provide the desired level of strength properties of steel, and more than 60% causes a significant increase in rolling force (which is not always possible to ensure ), and also leads to increased flatness of the foxes.

Two-stage tempering is carried out to further improve the strength properties of steel and flatness of sheets. Heating up to 350-450 ° C (2nd stage) provides the optimal combination of strength and plastic properties of steel due to the release of b-carbides in martensite deformation. Tempering at temperatures below the indicated ones does not ensure sufficiently intensive processes of hardening in steel and Bbmie 450 C leads to a decrease in the strength properties of the steel as a result of the reverse oi - process.

Due to the fact that the sheets have significant dimensions (thickness 1-5 mm, width 1000-2000 mm, length 1500-6000 mm) it is necessary to provide for preheating to 150-250 ° С (1st stage), which will provide more uniform subsequent heating to 350–450 ° C, and, consequently, obtaining a uniform metal structure over the entire cross section of the sheets.

Duration 1-3 h on the 1st stage due to the need

832

equalizing the temperature throughout the cross section of the metal, and an exposure of 2-6 hours at the 2nd stage is necessary for the complete process of hardening in steel. With increasing the size of the sheets, the length of cutting both at the first and second stages of tempering increases.

In order to obtain sheets with an increased flatness, their two-stage tempering is carried out in the under-turned state between flat support plates. Depending on the purpose of the sheets, tempering is carried out in furnaces with a protective or oxidizing atmosphere.

Example 1. Sheets with dimensions of 3.0x1300x1950 mm are made on austenitic corrosion-resistant steel of the following chemical composition,%: C 0.11, Mp 1.11, Si 0.46; P 0.03; S 0.014; Cr 18.1; Ni 11.0; W 0.12; Mo 0.17; Si 0.24; V 0.04; Ti 0.53.

The ingots smelted in an electroslag furnace are rolled on a slab, and then on sheets, which are subjected to quenching, pickling, and cold rolling with a total reduction of 20%. Quenching is carried out in a continuous furnace at 1080-1100 ° C with cooling in water.

Two-stage sheet tempering is carried out in an industrial bell-type furnace between flat base plates. The specific pressure is 0.03 MPa according to the following mode: heating to 150 ° C, holding for 1 hour, heating to 350 ° C, holding for 2 hours, cooling under the hood to 150-200 ° C and then in air.

The first stage ensures uniform heating of the sheets over the cross section to temperatures that virtually exclude the occurrence of hardening processes in steel. Further heating, up to 350 ° C and latching for 2 hours, ensures a uniform course of hardening processes over the entire cross section of the sheets. Heating and blowing out the sheets at the indicated temperatures in the under-heated state between the flat base plates allows to obtain sheets with high flatness, I

EXAMPLE 2 Under conditions similar to example 1, the sheets are cold-deformed with a total reduction of 60%, and tempering is carried out in the following mode: heating to 250 ° C, holding for 1 hour, heating to 450 s, you

cooling o /

2 h

up to 150-200 From the air.

under yes - The results of the study of strength properties and deviations from flatness of sheets obtained by the proposed and known methods are shown in the table.

The experiments carried out show that the obtained sheets have high strength properties and low values of non-flatness indicators in comparison with the sheets made by a known method.

Famous

15

thirty

Proposed

20

60

Compiled by A. Kulemin Editor N. Egorova Tehred L. Serdyukova

Order 1383/21 Circulation 550 Subscription

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, st. Project, 4

51834

Claims (1)

The invention The method of manufacturing large sheets, mainly from austenitic corrosion-resistant steels, including hot rolling, quenching, pickling and cold rolling, in order to improve the quality of the sheets by improving the strength properties and flatness, cold rolling is carried out -with a compression of 20-60%, then the sheets are collected in bags, placed between flat support plates and staggered at the same time at the beginning for fO J5 condition, at 150-250 ° C for 1-3 hours, and however, at 350-450 C for 2-6 hours 210-220 five 285-295 610 vy1 h, vy2 h vy1 h, vy2 h 325-335 63 400-415 b4 Proof-reader I.Erdeyi