SU1668426A1 - Method for heating blanks - Google Patents

Abstract

This invention relates to metallurgy, in particular to methods for heating billets in continuous fiery furnaces. The purpose of the invention is to improve the quality of heating and furnace performance. The method includes a two-sided heat supply to the workpiece, heating its surface up to 1225 - 1255 ° C, thermal insulation for the time defined by from the expression Τ _t = K _1? T ^K ₂ (Τ _n / L) ^K _3, wherein Τ _m - length thermal insulation of the workpiece, min

δT is the difference between the surface temperature of the workpiece and the heating temperature of the metal for hot deformation, deg.

Τ _n - the duration of the heating of the workpiece, min

L is the size of the workpiece in the direction of heat supply, cm

K ₁ , K ₂ , K ₃ are empirical coefficients depending on the properties of the heated metal, K ₁ = 0.6 ... 0.9 min, K ₂ = 0.68 ... 0.72, K ₃ = ( -0.08) ... (- 0.12). 5 tab.

Description

The invention relates to ferrous metallurgy, and in particular to methods for heating billets in passing flame furnaces prior to pressure treatment.

The purpose of the invention is to improve the quality of heating and furnace performance.

PRI me R. In the methodical pusher-type heating furnace, billets are heated with a cross section of 100x100 mm. The material of the blanks - low carbon structural steel St.St. The desired heating temperature of the workpieces is 1210 ° C. The heating time is 65 minutes.

Heating is carried out by applying heat from two sides until the temperature of the surface of the workpiece reaches 15–45 ° C higher than the temperature of hot deformation, i.e. to 1225-1255 ° C. A smaller value from the specified range corresponds to a longer heating time, and a larger one to a shorter one. The range selection is based on Table 1.

From table 1 it follows that the difference between the temperature of the surface of the workpiece and a given temperature of heating of the metal should be selected from the range of 15-45 ° C. In this case, with moderate fuel consumption, the furnace productivity is high, and the average integral temperature of the workpiece can deviate only slightly from the set one (by 1–8%).

With a temperature difference of At 15 ° C, the average integral temperature of the workpiece deviates from the set by 24-38%, and the productivity of the furnace decreases in comparison with the design by 8%. Thus, the heating quality of the blanks and the productivity of the furnace are reduced.

(L

WITH

about about

&

KZ

about

When the temperature difference is At 45 ° C, the deviation of the average integral temperature from the given one is 23-37%. At the same time, the productivity of the furnace increases slightly (within 4% as compared to the design), and the fuel consumption increases significantly (by 15%). Consequently, in this case, while maintaining performance close to the design, the heating quality of the workpieces significantly decreases and the fuel consumption significantly increases.

After the heating process is completed, the workpiece is thermally insulated, as a result of which the temperature is equalized over its cross section. The duration of thermal insulation is determined from the ratio

TT Ki DgK2 (gn / 1);

h

where tt is the duration of the thermal insulation of the workpiece, min;

At is the difference between the temperature of the surface of the workpiece and the temperature of heating of the metal for hot deformation, deg;

gn - duration of heating the workpiece, min;

 - the size of the workpiece in the direction of heat supply, cm;

Ki, "2, Kz - empirical coefficients depending on the properties of the heated metal, KiK), 6 ... 0.9 min,, 68 .. 0.72, Kz (-0.08) ... (- 0 ,12).

The ranges of empirical coefficients are justified by the table.2.

From Table 2 it follows that the values of empirical coefficients should be selected from the range of 6-0.9 min., 68-0.72, Cs (-0.08) - (- 0.12). in this case, normal heating quality is ensured. The temperature difference over the cross section of the workpiece does not exceed 12 ° C. At К 1 0.6 min, Кз - 0.12, the temperature difference over the cross section of the workpiece after its thermal insulation is complete can reach 32-164 ° C, which exceeds the maximum permissible values. With Ki 0.9, K2 0.72, Kz-0.08, the temperature difference across the cross section of the workpiece is not high, but in this case, the productivity of the furnace is significantly reduced. In addition, significant capital expenditures are required for the construction of a thermoelectric zone.

Duration of thermal insulation, 6 (1255-1210) ° 68 (65/10), 4 min.

The results of the calculation of the duration of thermal insulation for the boundary conditions, as well as the data on the heating quality and furnace performance after these treatments are given in Table 3. After the completion of the thermal insulation process, the temperature difference across the cross section of the workpiece (100x100 mm) is 8 ° C. Further, the billet is sent for subsequent rolling. The billet is heated by a known method. The heating mode is given in table.4.

- Comparative data after heating on the proposed and known methods are given in table.5.

Thus, the proposed method of heating the blanks improves the quality of heating (the temperature difference across the cross section of the blanks decreases to 0-8 ° C) and improves the kiln performance by 1-3% {the duration of heating the blanks is reduced by 1-4 minutes) .

Claims (1)

Invention Formula The method of heating billets, including a two-way heat supply, is also distinguished by the fact that, in order to improve the quality of heating and furnace performance, the billet is heated to its surface temperature of 1225-1255 ° C, then the billet is thermally insulated for a time determined from the ratio tt (th / l) k3. min where rm is the duration of the thermal insulation of the workpiece, min; At is the difference between the temperature of the surface of the workpiece and the temperature of heating of the metal for hot deformation, deg; gn - duration of heating the workpiece, min; I - the size of the workpiece in the direction of heat, cm; KI, K2, Kz - empirical coefficients depending on the properties of the heated metal,, 6 ... 0.9 min,, 68 ... 0.72, Kz (-0.08) ... ( -0.12). 15 45 0.62-0.76 0.92-0.94 0.99-1.01 1.06-1.08 1.23-1.37 Decrease in productivity by 8% in comparison with the project Increased productivity by 1% compared with the design Productivity increase furnaces at 27, in comparison with the design Moderate fuel consumption Oven capacity increase by 3% in comparison with the design Increased furnace productivity by 4% compared with the design. Increased fuel consumption by 15x Less than 0.68 Less than 0.12 32-164 More than 0.72 More than -0.08 0-11 0.68-0.72 (-0.08) - 0-12 (-0.12) Table 2 The temperature does not have time to level Normal quality of heating Low productivity high capital costs Table 3 159,151,164,147 At the beginning of the method 15-30 0-4 20-35 3-6 25-40 5-8 Table 4 Table 5 3-4 2-3 1-2