RU2528564C2 - Preparation of powder wire mix and device to determine natural slope angle of powder material - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to powder metallurgy, particularly, to production of welding powder wire. It can be used for production of whatever type of powder wires. Said mix is prepared by drying and screening of every component through screen #0315 or #02, said components being dosed and mixed. Obtained mix natural slope angle is defined with the help of funnel made of stainless nonmagnetic steel, funnel tape making 9-22 degrees, and by polishing inner surface to Ra of 0.01-0.16 mcm. It is compared to standard angle and corrected at changing of the mix granulometric composition. Every component is pre-sieved to define said angle for every fraction of all components. At natural slope angle larger than upper limit of standard magnitude fine fractions are removed to add coarse fractions. At natural slope angle smaller than lower limit of standard magnitude coarse fractions are removed to add fine fractions. Proposed device comprises bed 1, funnel drive composed of guide posts for displacement of funnel 2, ring 5 connected therewith and funnel height meter 2 composed by measuring scale 8 arranged at the bed and equipped with vernier scale 9m funnel 2 connected with the ring, and flat disc, funnel taper making 9-22 degrees. Note here that funnel 2 and flat disc 3 have working surfaces finished to Ra 0.01-0.16 mcm.

EFFECT: higher quality of powder wire mix, higher accuracy of natural slope angle determination.

5 cl, 6 dwg

Description

The invention relates to welding production, in particular to a method for preparing a charge for welding flux-cored wire. and can be used in the manufacture of other types of cored wires.

A known method of preparing a charge of flux-cored wire (Production of surfaced flux-cored wire of grades 25X5FMS, 35V9X3SF, 18X1G1M, 14GST, 80X20R3T, 100X4G2AR, X10V14, SP-10 and welding grade SP-10. Technological instruction TI MMK-METIZ PP 1, 2006, p. 16-18), including drying and sieving the components through a No. 0315 sieve to obtain a sublattice product in the form of a mixture of particles with a minimum size of less than 50 microns and a maximum size of less than 0.315, the dosage of the components according to the formulation of the charge of a particular brand of cored wire and their subsequent mixing into a mixture body.

The disadvantage of this method is that in the known method they do not control the fractional composition of the components, but only limit the maximum particle size, for example 0.315 mm, when sifting through sieve No. 0315, which negatively affects the flowability of the charge, and therefore its quality. Therefore, the resulting multicomponent charge often does not correspond to the uniformity of the chemical and particle size distribution, which causes subsequent uneven filling of the volume of the wire sheath, since the charge has either high flowability and is prone to segregation and delamination or low flowability and is prone to freezing and collapse when filling cored wire .

A known method of preparation of the charge (Pacekin V.P., Rakhimov K.Z. Production of cored wire.- M .: Metallurgy, 1979, p.25-31), including the operation of grinding, classification, drying, dosing of components and mixing the mixture . In the known method, sieving is carried out on sieves No. 025 to No. 005 and the residue on the sieves is determined. However, this method is aimed at solving the problem of controlling the composition of the charge at the stage of the operation of grinding the bulk material with an indication of a wide range of acceptable fractions. Therefore, the mixture has the same disadvantages as the above analogue.

This is because in the known methods do not check all incoming components of the charge for flowability. To obtain the most homogeneous mixture when mixing various powder components, it is necessary that their flowability is approximately the same. At low flowability, the charge is not uniform due to its “freezing” in the hopper and uneven feeding into the volume of the wire being wrapped. With high flowability of the charge, the phenomenon of segregation of material particles is observed, i.e. separation into large heavy fractions, which roll down to the walls of the bunker, and into small fractions, which are concentrated in the zone of the outflow channel. Therefore, the charge discharged from the hopper differs from the charge filled in it by the fractional and chemical composition.

The problem solved by the invention is to improve the quality of cored wire.

The technical result of the invention is to improve the quality of the mixture of flux-cored wire by increasing its uniformity in chemical and particle size distribution.

The specified technical result is achieved by the fact that in the method of preparing the charge for the flux-cored wire from predetermined components, including drying and sieving each component through a sieve No. 0315, or through a sieve No. 02, the dosage of the components and their mixing, according to the invention, preliminarily determine the angle of repose ( ЕО) of the obtained mixture using a device for determining the angle of repose of powder materials containing a funnel made of stainless non-magnetic steel with a taper of 9–22 ° and polishing the internal surface Ra within 0.01 ÷ 0.16 μm, compare it with the reference angle ЕО and adjust the angle ЕО of the resulting mixture by changing the particle size distribution of its components, for which preliminary screening of each component is carried out and the angle ЕО of each fraction of all components is determined charge, at an angle ЕО of the charge exceeding the upper limit of the reference angle ЕО, remove small fractions and add large fractions of components, and at an angle ЕО of the charge less than the lower limit of the reference angle ЕО, remove large ones and add small fractions tion components, wherein the reference angle is 36 EO charge ÷ 42 °

The quality of the preparation of the mixture from a multicomponent mixture of powders in the form of metals, ferroalloys, minerals, organic substances depends on the storage conditions and physico-chemical parameters of the incoming components, namely bulk and specific gravity, degree of grinding, particle size distribution, humidity, autogesia, internal friction, which can vary over wide ranges.

 The control of all these factors is a rather laborious process, therefore their support at the required level is practically impossible. An imbalance in the fractional composition leads to poor flowability when there are many small fractions, while the mixture freezes in the hopper, and the wire is obtained with voids. Or with an excess of coarse fractions, when the charge becomes too loose, and in the process of making the wire, it undergoes segregation and delamination, which leads to an uneven chemical and particle size distribution of the charge along the length of the cored wire.

The physicochemical properties of the components of the mixture affect the flowability of the powder material, which is a comprehensive indicator of the quality of the prepared mixture, and is determined by the angle of repose of the mixture. It was experimentally established that a mixture with an optimal fractional composition has an EO angle in the range 36–42 °. In this case, it mixes well enough, has good flowability and fills the cored wire well.

The quality of preparation of the charge depends on the accuracy of determining the angle EO of the charge or its individual components. The determination of the ЕО angle with the aid of a funnel selected in accordance with the composition of the charge and made of stainless non-magnetic steel with a taper of 9–22 ° and polishing of the inner surface Ra in the range of 0.01–0.16 μm makes it possible to determine the EO angle with reliable accuracy . The specified funnel ensures the outflow of powder material in hydraulic form when there are no fixed zones, and also the channel is not formed in the powder material in the form of a funnel or pipe. This contributes to an optimum flow rate of the powder material. When comparing the angle ЕО of the prepared mixture with the reference angle ЕО, a conclusion is made about its suitability or the need for fractional adjustment.

Figure 1 shows table 1 with the results of determining the angle EO fractions of the components.

Figure 2 shows table 2 with the results of determining the remainder of the components on the sieves.

Figure 3 shows table 3 with the results of calculating the mass fraction of fractions of the components in the charge.

Figure 4 shows table 4 with the results of determining the remainder of the components on the sieves after adjusting the particle size distribution.

The method of preparation of the mixture is as follows. Check the moisture content of the powder components. When humidity is more than 0.5% wt. they are dried at 200-250 ° C for an hour, then the components are sieved through a No. 0315 or No. 02 sieve according to GOST 6613-86, depending on the final wire diameter.

A mixture is prepared from the components obtained after sifting according to the recipe for a particular brand of cored wire. An example of a method of preparing a mixture of the following formulation,% wt. Fe powder - 50, FeMn - 10, CaCO ₃ - 40. To prepare 1000 g of the mixture, weigh Fe powder - 500 g, FeMn - 100 g, CaCO ₃ - 400 g. The mixture is mixed in a mixer at a rotation speed of 13 ± 1 rpm min for 40-60 minutes For this charge, select a funnel to determine the angle EO of the charge with a taper of 15 ° and polishing its inner surface Ra of 0.08 μm. The angle EO of the charge β is determined, which is the angle between the base and the generatrix of the cone formed by free vertical filling of the charge particles onto the horizontal plane, which turns out to be 34.5 °. Angle β characterizes the main indicator of the charge - flowability. Compare the resulting angle EO of the charge with a reference angle EO equal to 36-42 °. To obtain a high-quality mixture with a homogeneous chemical and particle size distribution, it is necessary to increase the angle EO of the mixture to the limits of the reference angle EO. For this, the granulometric composition of each component is determined by sieving it on sieves with different mesh sizes in millimeters: 0.315; 0.2; 0.16; 0.1; 0.063; 0.05. The mixture passing through the previous sieve is sieved on a subsequent sieve, namely, the mixture passing through sieve No. 0315 is dispersed through sieve No. 02, the charge passing through it is dispersed through sieve No. 016, etc. to sieve No. 005. The fraction of the charge passed through a No. 005 sieve is considered dusty (fine) and is designated -005 (minus).

Then determine the flowability of each fraction of all components by determining the angle EO of each fraction of all components (table 1 in Fig. 1). After that, each fraction is weighed and find its percentage in the volume of the charge (table 2 in figure 2). The sum of the percentage of all fractions of this component is 100% wt.

The mass fraction of each fraction of each component in the mixture is determined based on the percentage of the component in the mixture and its fractional composition.

The mass fraction of fraction 02 for Fe powder in the mixture is equal to:

m ₁₁ = 0.5 · 0.166 = 0.083,

where 0.5 is the proportion of Fe powder in the mixture (content of 50% wt .;

0.166 - the proportion of fraction 02 in Fe powder (content 16.6% wt.) And so on (row 1 of table 3).

The mass fraction of fraction 02 for FeMn in the charge is

m ₂₁ = 0.1 · 0.302 = 0.0302,

where 0.1 is the proportion of FeMn in the mixture (content of 10% of the mass);

0.302 - fraction of fraction 02 in FeMn (content 30.2% wt.) And so on (row of table 3).

The mass fraction of fraction 02 for CaCO ₃ in the mixture is equal to:

m ₃₁ = 0.4 · 0.273 = 0.1092,

where 0.4 is the proportion of CaCO ₃ in the mixture (content of 40% wt .;

0.273 is the fraction of fraction 02 in CaCO ₃ (content 27.3% wt.) And so on (row 3 of table 3).

In this case, the sum of all mass fractions of all fractions of all components is equal to unity. Then determine the calculated angle EO of the given mixture based on the data of tables 1,2 and 3:

$${\beta }_{w\mathrm{and}xts}={\displaystyle \sum _{k=\mathrm{one}}^{\mathrm{TO}}{\displaystyle \sum _{n=\mathrm{one}}^N{m}_{kn}\cdot {\beta }_{kn},\text{Where}\left(\text{one}\right)}}$$

k is the component number;

n is the number of the fraction;

K is the number of components;

N is the number of fractions;

m is the mass fraction of the nth fraction of the kth component;

β is the angle of repose of the nth fraction of the kth component.

The calculated angle ЕО of the charge obtained by the formula (1) is 34.42 °, which practically corresponds to the angle of ЕО of the mixture measured with a funnel equal to 34.5 °. However, the charge with an angle EO equal to 34.5 °, which is not included in the range of values of the reference angle EO equal to 36 ÷ 42 °, does not correspond to the required quality for flowability. Therefore, it is necessary to adjust the fractional composition of the mixture to increase the angle EO, for example, up to 38 °. From table 2 it is seen that the fractions of -005 have the largest EO angles; therefore, the number of fractions -005 FeMn and CaCO _{3 is} increased and, accordingly, the number of fractions with small EO angles is reduced, for example, 02 and 016. Table 4 (Fig. 4) shows adjusted particle size distribution of the charge components.

, то есть очень близкий к заданному углу, который находится в требуемом диапазоне эталонного угла ЕО.By performing calculations similar to those described above by formula (1), with other mass fractions of fractions 02, 016 and -005, FeMn and CaCO ₃ get the corrected charge angle EO equal to $${\beta }_{w\mathrm{and}xts}^{\mathrm{from}\mathrm{to}\mathrm{about}RR}={37.44}^{\circ }$$

, that is, very close to a given angle, which is in the desired range of the reference angle EO.

In the case of too many fractions of -005 with large angles EO, the angle EO of the charge may be greater than 42 °. Then, when adjusting, it is necessary to reduce the amount of -005 fraction in FeMn and CaCO ₃ and increase the number of fractions with smaller EO angles, for example, 02, 016, 01, and again make a similar calculation of the EO angle of the charge.

The inventive method allows you to adjust the particle size distribution of the mixture of any formulation with any number of components included in it.

Thus, ensuring the optimal particle size distribution of the charge can significantly improve the quality of the charge, and therefore, the quality of welding flux-cored wires.

A device is known for determining the angle EO of powder materials, containing two adjacent vertical walls made of organic glass and installed on the base, a metal conical funnel with a cone angle of 60 °, installed at the junction of adjacent walls, one of which carries risks corresponding to different angles in degrees (see GOST 28254-89). The test product is poured through a metal funnel into the device until the top of the filling is equal to the top of the funnel. The angle of the EO is determined in accordance with the risks applied to the wall.

The disadvantage of this device is the inability to accurately measure the angle of the SW according to the risks incurred on one of the vertical walls. In addition, the measurement does not take into account the inevitably occurring curvatures of the slope of the cone, as well as deviations of the base contour from the correct circle. And therefore, the degree of segregation, i.e. the distribution of particles by size, shape and density, causing distortion of the parameters of the cone of bulk material. These distortions are the greater, the higher the bulk density of the test powder material.

The closest is a device for determining the EO angle of powder materials (see Andrianov E.I. Methods for determining the structural and mechanical characteristics of powder materials.- M .: Chemistry, 1978, p.127), containing a funnel, a fixed base in the form of a horizontal flat disk , a measuring instrument in the form of a ruler and a sight.

A disadvantage of the known device is the high rate of particle fall, the low accuracy of the measurements with a ruler and a target, as well as the extrapolation of the slopes to find the position of the geometrical vertex of the cone.

The technical result of the invention is improving the quality of the charge for cored wire by increasing the accuracy of determining the angle of repose of powder materials.

The specified technical result is achieved by the fact that in the device for determining the angle EO of powder materials, including a base, a funnel mounted with the possibility of vertical movement and made in the form of a cone, a flat disk mounted on the base, and a measuring device according to the invention, it further comprises means funnel movement, made in the form of guide racks mounted on the base, a ring for attaching a funnel connected to the racks, and means for measuring the height of the funnel, you filled in the form of a measuring scale mounted on the base, equipped with a movable vernier scale connected to the ring, the funnel is made of stainless non-magnetic steel with a taper in the range of 9-22 °, while the working surfaces of the funnel and flat disk are polished within Ra 0, 01 ÷ 0.16 μm. In embodiments of the invention, the funnel and flat disk are made of 12X18H10T steel, the base is equipped with adjustable supports, a cylindrical level and a ground screw.

The presence of the funnel moving means in the vertical direction, made in the form of guide racks, on which the ring for fastening the funnel is fixed, allows you to smoothly move the funnel in a strictly perpendicular direction without jerks and vibrations, which ensures the stability of the measurement results.

The segregated material is mixed in the funnel of the proposed design and its averaging is ensured, which makes it possible to stably obtain a bulk cone of geometrically regular shape, and therefore, increase the accuracy of measuring its parameters, which is necessary to improve the quality of the charge for flux-cored wire.

When the funnel taper is more than 22 °, the outflow of the powder material will be unstable due to the development of the phenomenon of arch formation and subsequent collapse due to the formation of a channel caused by segregation and delamination of the powder material. When the funnel taper is less than 9 °, there is practically no averaging of the material segregated when backfilled into the funnel, since in this case the powder material moves uniformly in it like a solid body.

The implementation of the funnel made of non-magnetic stainless steel 12X18H10T makes the funnel durable and retains its geometric dimensions during operation, while it does not affect ferromagnetic powder materials, which increases the accuracy of determining the angle EO of powder materials.

The claimed essential features of the invention, predetermining the receipt of the specified technical result, do not explicitly follow from the prior art, which allows us to conclude that the invention meets the conditions of patentability "novelty" and "inventive step".

In FIG. 5 shows table 5 with the angles of repose of the charge of a typical and adjusted compositions.

In FIG. 6 shows a general view of the device.

A device for determining the angle of repose of powder materials (Fig. 6) includes a base 1, a funnel 2, mounted with the possibility of vertical movement and made in the form of a cone, a flat disk 3, means for moving the funnel 2, made in the form of guide racks 4, mounted on the base 1, rings 5 for attaching a funnel 2, connected to the uprights by means of bushings 6 and connecting rods 7, and means for measuring the height of the funnel, made in the form of a measuring scale 8, equipped with a movable vernier scale oh 9 with a division value of 0.1 mm, connected by a plate 10 to one of the bushings 6. Funnel 2 is made of non-magnetic stainless steel 12X18H10T with a taper of 9 ÷ 22 ° and polished inner surface Ra in the range of 0.01 ÷ 0.16 μm . The base is equipped with adjustable supports 11 and for determining the strictly horizontal position of the base 1 with a cylindrical level 12. To remove the electrostatic charge that may accumulate on the device during the work with powder materials and adversely affect the measurement accuracy, grounding screw 13 is installed on the base 1. Disk 3 fixed on the base 1 by a pin 14, while the axis of the pin 14 passes through the center of the disk 3. The disk 3 is made of non-magnetic stainless steel 12X18H10T with polishing of the outer surface Ra within 0.01 ÷ 0.16 μm, which provides increased accuracy and stability of the measurement results. The angle between the plane of the disk 3 and the axis of the funnel 2 is 90 ÷ 0.1 °, while the axis of the funnel 2 coincides with the center of the disk 3. The sleeve 6 is equipped with a locking screw 15.

The device operates as follows. Ground the device using screw 13. Then, adjusting the height of the support 11, bring the base 1 with a flat disk 3 fixed to it in a horizontal position. Horizontal control is carried out using a cylindrical level 12. After releasing the locking screw 15, the funnel 2 fixed in the ring 5 is lowered until the plane of its outlet opening contacts the plane of the disk 3. In this position of the funnel 2, the divisions on the measuring scale 8 and nonius scale 9 show the value "zero". Next, powder material is poured into the funnel 2. Depending on the type of powder, the volume of material required to determine the angle of EO can be 50-100 cm ³ , with smaller values of the volume taken for powder material with a larger bulk mass. Holding the ring 5, the funnel 2 is smoothly raised along the guide racks 4, while the powder material pours out through its outlet into the horizontal plane of the disk 3 and forms a truncated cone 16 of the powder material. The rate of rise of the funnel 2 should coincide with the rate of outflow of the powder material through its outlet, providing a minimum velocity of particles of powder to the slope of the truncated cone 16. The speed of the rise of the funnel 2 is monitored visually. At a low rate of rise of the funnel 2, the powder precipitates with pulsations; at a high speed, the mass of the precipitating powder per unit time increases sharply. In both cases, there is an increase in the rate of arrival of the particles of the powder material on the slope of the powdered truncated cone 16 contributes to the formation of an unstable slope surface and ultimately leads to a decrease in the accuracy of determining the angle EO. The filling is carried out until a stable slope surface is formed and the base of the truncated cone 16 of the edges of the flat disk 3 is reached. In this case, the base of the truncated cone 16, limited by the edges of the flat disk 3, strictly corresponds to its diameter. The slope surface at the base of the truncated cone 16 is not curved due to the fact that a small part of the powder falls from the flat disk 3 onto the base 1. At the moment the base of the truncated cone 16 reaches the edges of the disk 3, the funnel 2 is stopped and its position is fixed using the locking screw 15. At the same time, some of the test powder material should remain in the funnel 2 so that as a result of the precipitation of the powder a truncated cone 16 is formed having a diameter at the apex equal to the diameter of the outlet opening ment of the funnel 2, wherein the slope surface at the top of truncated cone 16 has no distortion. The height of the truncated cone 16 is determined by the height of the raising of the funnel 6 with an accuracy of ± 0.1 mm on a scale of 8 and vernier scale 9.

The angle between the plane of the disk 3 and the generatrix of the formed truncated cone 16 is the angle EO β of this powder material and is calculated by the formula:

$$\beta =ac\mathrm{<figure-callout\; id="2"\; label="r\; t\; g"\; filenames="00000004.png,00000005.png"\; state="\{\{state\}\}">r\; </figure-callout>}tg\frac{2\cdot h}{D-d},\text{Where}\left(\text{2}\right)$$

D is the diameter of the flat disk 4;

d is the diameter of the outlet of the funnel;

h is the height of the truncated cone 16.

The inventive device was used to study the filling quality of a PP-SP-10 grade welding wire, the charge of which includes 9 powder components: iron powder, rutile concentrate, marble, fluorspar concentrate, ferromanganese, ferrosilicon, aluminum powder, sodium silicofluoride and ferrotitanium.

The results of measuring the angle EO β of the powder components are shown in table 5 in figure 5.

The values of the angles EO, calculated according to the results of measurements recorded using the proposed device, show that powder components with a typical particle size distribution have a large variation in the values of the angle β, namely from 30.01 to 44.69 °. To obtain a homogeneous mixture in this case is unlikely. After adjusting the particle size distribution of some components of the powder material by partially removing fractions of less than 0.05 mm and adding larger ones, or vice versa, the spread in the angle β decreases and ranges from 34.52 to 37.87 °. Therefore, such components will be better mixed, since their flowability is close.

The arithmetic mean of the results of three measurements is taken as the final test result. The discrepancy between the absolute values of the three measured angles should be no more than one degree.

Thus, the proposed device allows with high accuracy to measure the parameters of the angle EO of various powder materials and accurately determine the angle EO of the powder materials that make up the mixture. And also to select the required particle size distribution of the mixture in order to ensure the best miscibility of the components that make up the mixture. This ultimately improves the quality of the manufacture of cored wire.

Claims (5)

1. A device for determining the angle of repose of powder materials, including a base, a funnel mounted with the possibility of vertical movement and made in the form of a cone, a flat disk mounted on the base, and a measuring device, characterized in that it further comprises a funnel moving means made in the form of guide racks mounted on the base, rings for attaching a funnel connected to the racks, and means for measuring the height of the funnel, made in the form of measuring scales s mounted on the base and equipped with a movable vernier scale connected to the ring, while the funnel and flat disk are made of stainless non-magnetic steel with polishing of the working surfaces within Ra 0.01 ÷ 0.16 μm, and the funnel is made with taper within 9 ÷ 22 °. 2. The device according to claim 1, characterized in that the funnel and flat disk are made of steel 12X18H10T. 3. The device according to claim 1, characterized in that the base is equipped with adjustable supports, a cylindrical level and a ground screw. 4. A method of preparing a charge for a flux-cored wire from predetermined components, including drying and sieving each powder component through a No. 0315 sieve or No. 02 sieve, dosing the components and mixing them in a mixer, characterized in that they determine the angle of repose of the mixture using a device for determining the angle of repose of powder materials according to any one of paragraphs. 1-3, carry out its comparison with the reference angle of repose and adjust the angle of repose of the resulting mixture by changing the particle size distribution of its components, for which preliminary screening of each powder component is carried out and the angle of repose of each fraction of all components is determined, with the angle of repose exceeding the upper limit of the reference angle of repose, remove small and add large fractions of the components, and when the angle of repose is less than the lower limit the reference angle of repose is removed large and add small fractions of the components. 5. The method according to claim 4, characterized in that the reference angle of repose of the charge is 36-42 °.

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