RU2299103C1 - Composition-material blanks hot rolling method (variants) - Google Patents

Abstract

FIELD: processes and equipment for hot rolling of blanks of composition steel materials.

SUBSTANCE: method comprises steps of uniformly heating blank till temperature 950 -1200°C and reducing it at least during one pass in rolling stand at providing elongation factor for pass 1.2 - 2.5. In variant of invention blank may be heated till temperature 800 -950°C and in such case reduction is realized with elongation factor for pass 1.2 - 2.5.

EFFECT: possibility for providing improved deformation condition in the mostly hard-to-deformable region of material due to taking into account mutual influence factor of regions of composition material.

12 cl, 3 dwg, 5 tbl

Description

The invention relates to the field of hot rolling of iron-based alloys, in particular to the hot rolling of billets of composite steel material containing a connected core and surface layer made respectively of ordinary and corrosion-resistant steel.

The use of corrosion-resistant layered materials allows to achieve the economy of scarce alloying elements, such as nickel, molybdenum, chromium, in the manufacture of products designed for difficult operating conditions, since only the surface (cladding) layer in these products contains deficient alloying elements.

By common steel, it is understood that widespread steels do not possess increased corrosion resistance, including low-carbon, carbon, low or medium alloy steels, electrical steel, and also steel alloyed with silicon in an amount of 1.5 to 6%.

Widely known are the methods for the production and rolling of sheet composite products, disclosed, for example, in the book “Technology of Laminated Metals”, Moscow: Metallurgy, 1991, authors Kobelev AG, Potapov IN, Kuznetsov EV, p. 113-114. In particular, the known method involves heating a rolling billet, consisting of a core and a surface cladding layer, made respectively of ordinary and corrosion-resistant steel, to a temperature of rolling at a level of more than 1220 ° C, and subsequent compression in thickness with a value of not more than 5 % per pass.

Also known is a method of hot rolling a thin-sheet steel composite billet with a stainless steel surface layer, disclosed in the book "Production of metal laminated composite materials", M .: Intermet Engineering, 2002, pp. 208-209, including heating a billet consisting of a core and a surface cladding layer, respectively made of ordinary and corrosion-resistant steel, to a temperature of rolling at a level of more than 1240 ° C, and subsequent compression.

In known methods, the rolling mode is selected so as to ensure the rolling of the most difficult to deform steel. Thus, although in the composite steel material the core and surface layers of steel vary significantly in properties, for example, the coefficient of linear expansion can vary several times, when choosing a rolling mode, they are often guided by the need to use a rolling mode related to more alloyed and, accordingly, difficult to deform steel , which reduces the efficiency of the rolling process, since it often leads to the occurrence of marriage, caused by uneven deformation of the cores and the surface layer.

In addition, the manufacture of only sheet products, provided in the known methods, does not allow sufficient use of composite steel materials, since there is a need for products that relate to long products: rods, wire rod, bent profiles, etc.

Numerous experiments conducted by the inventors of the present invention have shown that in the manufacture of high-quality products from composite steel material by means of rolling in calibers and when using a rolling mode adapted for a surface clad layer, which usually consists of corrosion-resistant steel, overfilling of gauges often occurs and a "mustache" is formed, making further rolling impossible and leading to marriage.

Thus, today there is a problem of rolling in calibers of billets made of composite steel material.

Based on the foregoing, the objective of the present invention is to provide a method for hot rolling of a billet from composite steel material, which provides for the production of long products with a core of ordinary steel and a surface layer of corrosion-resistant steel.

The technical result of the invention is to reduce rejects during high-quality rolling of billets of composite steel material containing a surface layer of corrosion-resistant steel.

According to the authors of the present invention, it is rather difficult to develop or select the mode of high-quality rolling of a composite steel product, based only on the characteristics of the surface layer or the most difficult to deform layer.

The basis of the proposed invention is the idea of developing a rolling mode for a composite steel material made of several layers and containing at least a surface layer of corrosion-resistant steel and a core of ordinary steel.

Thus, the authors proceed from the fact that a composite material is subjected to rolling, having different composition and properties in the core and in the surface layer, and not heterogeneous, mechanically connected layers, and therefore during rolling there is a mutual influence of the core on the deformation characteristics of the surface layer of the composite steel material and vice versa. Due to the mutual influence of areas of composite steel material having different composition and properties, the deformation conditions in the most difficult to deform region of the material can be facilitated.

Based on the above approach, the authors developed modes of high-quality rolling of billets from composite steel material.

To solve the problem, according to the present invention, a method for hot rolling of billets from a composite steel material containing a connected core and a surface layer made respectively of ordinary and corrosion-resistant steel, in which the billet is uniformly heated to a temperature of 950-1200 ° C, and the subsequent compression of the workpiece in at least one pass in the rolling stand, with a coefficient of extraction per pass of not more than 1.2, while before and / or during rolling comfort surface temperature of the composite steel billet.

In another embodiment, the problem is solved in the method of hot rolling of billets from a composite steel material containing a connected core and surface layer, respectively made of ordinary and corrosion-resistant steel, in which the billet is uniformly heated to a temperature of 800-950 ° C and subsequent compression billets for at least one pass in the rolling stand, providing a coefficient of extraction per pass 1.2-2.5, while before and / or during rolling control the surface temperature ozitsionnoy steel billets.

Preferred embodiments of the claimed invention provide for additional control of the surface temperature of the composite steel billet before rolling by cooling or additional heating, while the surface temperature is set in the range of 800-1000 ° C for high values of the coefficient of drawing and at the level of 950-1000 ° C for low extraction coefficient values. Additional temperature control allows you to create a temperature gradient in the workpiece over the thickness depending on the magnitude of the change in the properties of the composite steel material in the surface layer and in the core. When approaching the properties in the surface layer and in the core of the composite steel material, it is advisable to reduce the temperature gradient of the workpiece before rolling.

When rolling a workpiece in more than one pass, the workpiece can be heated between passes to compensate for heat loss, while the surface temperature of the workpiece is set at 800-1000 ° C.

It is preferable to carry out rolling in a two-roll mill stand with rolls having, depending on the production, a smooth barrel or a combination of vertical and horizontal calibres. Thus, the possibility of producing long products from composite steel material is provided on a wide range of equipment.

The following are examples of the implementation of the present invention for the manufacture of long products of various types.

On figa-1B shows various profiles of composite steel material obtained by rolling by the method according to the present invention and subjected to etching. As can be seen from the presented images, there are significant differences between the properties and composition of the surface zone and the core in the composite steel material, which should be taken into account.

Figure 2 presents the square and round blanks.

Figure 3 shows a gauge system for producing a round billet.

To obtain small sections, a two-roll mill with rolls with a diameter of 300 mm was used, while the rolls were calibrated or had a smooth barrel, depending on the type of rolled products. The following profiles were obtained at the mill: rectangle, strip, circle, square. The objective was to obtain the rental of the finest grade possible.

Getting a rental of rectangular section

Rectangular rolled products were obtained on rolls of the smooth barrel type. Two versions of bars of rectangular section were obtained: from a workpiece ⌀ 90 mm - 40 × 60 mm; from blanks ⌀ 60 and 70 mm - 18 × 30 mm. (Figa)

Before rolling, the billets were heated in a furnace to a temperature of 1200 ° C with a holding time of 35-40 minutes. The length of the blanks ranged from 400 to 500 mm.

Table 1 presents the values of the hood coefficients for each pass upon receipt of a 40 × 60 mm rectangular bar. The temperature of the workpiece before being fed to the rolls averaged 1170 ° C using an optical pyrometer. The temperature of the end of rolling was on average 980 ° C. Subsequently, part of the obtained rectangular rods was used as blanks for round rolling.

Table 1
Values of hoods
for a rectangular bar 40 × 60 mm Passage number one 2 3 four 5 6 7 8 9 10 eleven all Hood ratio 1,02 1,08 1.12 1,08 1,11 1.09 1.19 1.15 1.14 1,02 1,03 2.64

The values of the drawing coefficients for obtaining a rectangular bar of 18 × 30 mm are shown in Table 2. Upon receipt of these rods, the workpiece was heated after 6 passes, while the temperature of the workpiece was reduced to 850-900 ° С.

table 2
Values of hoods
for rectangular bar 18 × 30 mm Passage number one 2 3 four 5 6 7 8 9 10 eleven Hood ratio 1,02 1.17 1.19 1.20 1.20 1.20 1,11 1,04 1.06 1,03 1,07 Passage number 12 13 fourteen fifteen 16 17 eighteen 19 all Hood ratio 1,03 1.09 1,03 1,11 1,03 1.14 1,02 1,03 5.22

Getting strip

Stripes of 3 × 33 mm, 4 × 27 mm and 5 × 68 mm were obtained from an 18 × 30 mm rectangular bar on smooth barrel rolls (Figs. 1b, 1c). The rolling onset temperature was 1200 ° C. Table 3 presents the values of the coefficients of the hoods for each pass upon receipt of the strip 3 × 33 mm from the workpiece 18 × 30 mm Upon receipt of a strip of 3 × 33 mm, intermediate heating was carried out after 7 passes, while reducing the temperature of the workpiece to 850-900 ° C. No intermediate heating was performed for one of the bands, and the last passes were carried out at a temperature of about 700 ° C. On the surface of the strip there was a destruction of the stainless layer.

Table 3
Range hood values for a strip of 3 × 33 mm Passage number one 2 3 four 5 6 7 8 9 10 all Hood ratio 1.17 1.16 1,03 1,04 1,07 1.35 1.19 1.21 1.19 1,50 5.40

Getting a circle

To obtain a small-grade circle with a diameter of 25 mm, a calibration consisting of 6 calibers was selected: 3 horizontal ovals, 2 vertical and 1 circle. The system of calibers used to produce round products with a diameter of 25 mm is shown in FIG. The billets were heated in a furnace to a temperature of 1200 ° C. The rolling sequence is as follows: 3 passes through the 1st caliber and one pass through each subsequent, a total of 8 passes. Table 4 shows the values of the hood coefficients for each pass. Billets were rods of rectangular section 40 × 60 mm with a coating thickness of 3 mm and 8 mm.

Table 4 Passage number one 2 3 four 5 6 7 8 Hood ratio 1.13 1.19 1.12 1.21 1.28 1.29 1.43 1.66

When using the specified calibration and when the values of the coefficient of extraction per pass, exceeding 1.2, there was an overflow of caliber, which did not allow to obtain high-quality hire. The use of calibration, providing the values of the coefficient of extraction per pass, not exceeding 1.2, has led to high-quality round products. Figure 2 shows the resulting round hire. In the first rolling experiment with this calibration, the mill stand was not equipped with wiring. During the rolling of the billet, the temperature of the onset of rolling was 1100 ° C; twisting of the billets in a vertical gauge was noted. The use of roller wiring to hold the workpiece in vertical gauges solved the twisting problem. It was also tested undercoating the workpieces before the next pass to a temperature of up to 950-1000 ° C. The temperature was controlled by an optical pyrometer. This led to a high-quality profile in all calibres.

Getting square

To obtain the square (Figure 2), a round billet with a diameter of 68 mm was used. The rhombus-square calibration was used, which has two calibers: a horizontal rhombus and a vertical square. The rolling onset temperature was 1200 ° C. Rolling was carried out in four passes. Three consecutive passes through 1 caliber, with a decrease after each pass the distance between the rolls, and one through a square. In the third pass, for all calibration selection options, the coefficient of extraction did not exceed 1.25. The temperature of the workpiece before the third pass was 950 ° C. Table 5 presents the values of the rolling parameters in the rhombus-square gauge system, at which the best results were obtained.

Table 5 No.
about
move The form
caliber / profile Kantovka Height
N mm Width
In mm Area
F mm Δh
mm Δb
mm Coeff.
hoods 0 A circle 68.0 68.0 3632 one Rhombus 0 ° 65.5 72.5 3284 2,5 5.5 1,11 2 Rhombus 0 ° 55.5 78.5 2733 10.0 6.0 1.20 3 Rhombus 0 ° 47.5 90.0 2208 8.0 11.5 1.24 four Square on the edge 90 ° 57.0 57.1 1764 33.0 9.6 1.25 Total hood ratio: 2.06

Thus, the experiments showed that the proposed rolling mode allows high-quality long products from composite steel material consisting of a core and a surface layer made respectively of ordinary and corrosion-resistant steel. This ensures high quality of the products obtained and a low proportion of defective products.

Claims (12)

1. The method of hot rolling of billets of composite steel material containing a connected core and surface layer, respectively made of ordinary and corrosion-resistant steel, in which the billet is uniformly heated to a temperature of 950-1200 ° C, and subsequent compression of the billet is carried out at least one pass in a rolling stand, with a coefficient of extraction per pass of not more than 1.2, while the surface temperature of the workpiece is controlled before and / or during rolling. 2. The method according to claim 1, characterized in that the surface temperature of the billet of composite steel material before rolling by cooling or additional heating is set in the range of 950-1000 ° C. 3. The method according to claim 1 or 2, characterized in that the preform between the passages is heated to a surface temperature of 950-1000 ° C. 4. The method according to claim 1, characterized in that the rolling is carried out in a two-roll rolling mill with rolls equipped with vertical and / or horizontal gauges. 5. The method according to claim 4, characterized in that when rolling in vertical calibers, additional workpiece support is carried out, mainly by means of roller wiring. 6. The method according to claim 1, characterized in that the contactless determination of the surface temperature of the workpiece by means of a pyrometer is carried out. 7. The method of hot rolling of billets from composite steel material containing a connected core and surface layer, respectively, made of ordinary and corrosion-resistant steel, in which the billet is uniformly heated to a temperature of 800-950 ° C, and subsequent compression of the billet is carried out at least one pass in a rolling stand, ensuring a coefficient of extraction per pass 1.2-2.5, while the surface temperature of the workpiece is controlled before and / or during rolling. 8. The method according to claim 7, characterized in that the surface temperature of the billet of composite steel material before rolling by cooling or additional heating is set in the range of 800-1000 ° C. 9. The method according to claim 7 or 8, characterized in that the preform between the passages is heated to a surface temperature of 800-1000 ° C. 10. The method according to claim 7, characterized in that the rolling is carried out in a two-roll rolling mill with rolls equipped with vertical and / or horizontal calibers. 11. The method according to claim 10, characterized in that when rolling in vertical calibers, additional workpiece support is carried out, mainly by means of roller wiring. 12. The method according to claim 7, characterized in that the contactless determination of the surface temperature of the workpiece by means of a pyrometer is carried out.

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