SU1557111A1 - Method of final annealing of glassware - Google Patents

Abstract

The invention relates to the technology of annealing glass products made by hot pressing, and can be used for annealing glass products made of glass with low heat resistance and non-uniform composition. The aim of the invention is to increase the yield, increase the thermal strength of glass products. The outer and inner surfaces are heated to the glass softening temperature (T _P ), and the surface heating power density (Q) satisfies the relation

0.22≤QΤ / CD (T _P -T _O ) ≤0.3, and the heating time (Τ) is within 0.03≤AΤ / D ² ≤0.1, where C is the volumetric heat capacity of glass

D - glass wall thickness

A - thermal diffusivity of glass. Due to this, a decrease in surface residual stresses before loading into the annealing furnace, an increase in the heat resistance of glassware is achieved. 3 il.

Description

The invention relates to the technology of annealing glass products made by hot pressing, in particular, of glass with low heat resistance or which is heterogeneous in composition.

The purpose of the invention is to increase the yield, increase the thermal strength of glass <

Figure 1 shows a schematic representation of a device that implements the method of annealing glassware; Fig, 2 - the dependence of the average dimensionless temperature of the heated near-surface region of glassware

Ј (Tr-T7) c7 fig. 3, the dependence of the maximum

from the ratio

on

temperature gradient in glass from, respectively, and wearing f -j.

A device for annealing glassware 1 with a wall thickness d consists of two gas burners 2 and an annealing furnace 3. At the first stage, the internal and external surfaces of the glassware (cone) 1 are heated by gas burners 2. At the second stage, the glass-edeli is loaded into the annealing furnace.

qC

The ratio -yyr- describes cd (Tp-T0)

the process of heating the glass wall with a thickness d after heating with gas burners of intensity q during time C,

01

ate

After pressing the glassware as a result of the sharp cooling of the surface by the press tool, the remaining stresses occur on the surface area with a thickness of 1 Ј 0.13d. Therefore, it is sufficient to heat it to a temperature that ensures relaxation of the stresses in order to reduce these stresses. Therefore, an average temperature is considered.

- 1 G of the surface layer T Tdl,

To relax the voltage, it is sufficient to heat the layer under consideration to the glass softening temperature or to a DT x 40-50 ° C below. It is not possible to heat up to a temperature above the softening point of the glass, as the result of the effect of gravity begins to deform the surface of the glassware under the influence of its own weight. As can be seen from the indicated tempo zone

0.22 &

Ј 0.3.

The surface warming layer is reached if

c7 (Tr

At f 7 0.1, the temperature difference in glassware is less than 20% of the required difference in heating temperature. The temperature field is almost uniform in thickness and the product is heated almost equally both in the center and on the surface. At f 0, 1, the temperature difference begins to increase dramatically and practically takes place in the surface layers, which are heated as required for the case under consideration. The value should be limited to 0.03 below, since below this, if the condition is 0.22 i Ј 0.3, dangerous temperature gradients occur, the product is destroyed.

Q

five

five

0

five

An example of a specific use of the proposed technical solution and the proposed ratios of the technological parameters is considered in the production of 25LK2T.V-tube picture cones from glass during the transition period of the glass furnace.

When removing the 25LK2T kinescope cone from the automatic press carousel, the wall temperature is 300-350 ° C. Next, the cone enters the carousel for welding the anode, at two positions of which, before loading into the annealing furnace with the help of two gas burners located on the inner and outer surfaces of the cone, the surface layers of the cone heat up during time Ј.

The wall thickness of the 25LK2TS color kinescope cone is d 0.005 m, the average thermal diffusivity of the glass C94-1 from which the cone is made is, for the temperature range 0-1000 ° C and 0.4 x x, the volume heat capacity of the glass is 1.95-10 J / mk,

The glass softening temperature of C94-1 Tp is 550-570 ° C, and the surface temperature of the glass after pressing at the time when the cone is on the anode welding machine is T0 320 ° C.

For the given source data, the proposed ratios are calculated.

0.22

Ll

cd (Tp-T0)

 0.3

(ABOUT

WITH

From Ј. “N 1 (jj 4 iU, I

(2)

45

Substituting the initial data into ratios (1), (2), we obtain:

0.22 4

1.95-10 J / m3K-0.005 m (560-320)

About 4 10 4 m / s-C50 The heating time is 4 s, and

0.03 i 0.1. (4) heating power density (q) COOT

Consequently, it is composed of the formula (3 0.22

The calculations in (4) have that the value of € can be within

0.75 -10- 2.5-10b.

3rd. ".." Vige ™ -.- ™.

0.4, 4 -10-U

1.875 sec f 6.25 sec

Oh, h; (3)

heating power density (q) COOT

consequently, from formula (3) 0.22

2.34-Ю6 ° 3;

1.287-10s W / m, 755 -105 W / m7.

The heating intensity is 1.4-10 5 W / m2.

Claims (1)

Thus, the proposed method of annealing glassware eliminates the critical level of residual stresses in the surface layers of glass; improves the reliability and heat resistance of glass products, claims The method of annealing glass products by supplying them to a conveyor furnace and short-term intensive heating, characterized in that, in order to increase the yield, increase the thermal strength of glass products, heating is performed with a surface power density q satisfying the ratio 0.22 g 0.3, during time C, the satisfactory ratio 0.03 4 $ Ј0,1, where c is the volumetric heat capacity of the glass; d is the thickness of the glass; a - thermal diffusivity of glass; Tp is the temperature of softening glassware; 1Q is the initial temperature of glass products. / W //////// 7 // 77. Y /////////////////// A 1 aT CC1 (7p-G9)