RU2332430C1 - Metal-polymeric composition for manufacturing cast iron bars - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to powder metallurgy, namely to metal-polymeric compositions for obtaining cast iron bars. Metal-polymeric composition is obtained by mechanical mixing of two mixtures - as component of the first high-dispersion powders of iron and, probably, at least, one alloying element is used, as components of the second - thermo-reactive phenol-formaldehyde resin, plastificator and iron oxide powder are used, as plastificator salt of stearine acid is used, with the following ratio of components mass %: - thermoreactive phenolformaldehyde resin -15-20; -salt of stearine acid -0.4-1.5; -iron oxide (III) -0.2-32; -iron powder - the remaining part. As alloying element in the first mixture high-dispersion powder of nickel, chrome, copper, molybdenum, manganese, aliminium, titanium, vanadium, silicon is used.

EFFECT: reduction of technological cycle of manufacturing of cast iron products and expanding their range.

2 cl, 2 tbl, 2 ex

Description

The invention relates to powder metallurgy, and in particular to metal-polymer compositions for producing cast iron billets by molding and sintering.

Known metal-polymer compositions are plastics with a metal filler (iron, aluminum, etc.), which use thermoplastics as well as phenol-formaldehyde resins and other thermosets as a binder [1, 2]. These compositions are used without further processing, as materials with special physical and mechanical properties. In particular, a known composition containing 4.2% wt. phenol-formaldehyde resin and 95.8% wt. carbonyl iron, which is used for the manufacture of soft magnetic products by cold pressing and subsequent heat treatment at t = 130 ° C.

Also known are metal-polymer compositions, the so-called MIM feedstocks, which are a mixture of steel powders or iron powders and alloying elements and a binder based on thermoplastics, which are used to make steel billets with a material density close to theoretical by injection molding and subsequent sintering [ 3, 4].

However, the known metal-polymer compositions are unsuitable for the manufacture of cast iron billets due to the insufficient carbon content.

The closest in technical essence is a composition consisting of a mixture of thermosetting formaldehyde resin, plasticizer and carbonyl iron powders and suitable for materials with a carbon content of 5 ÷ 6% [5].

However, the use of this composition to obtain cast iron products requires the use of additional technological operations to ensure a given carbon content.

The invention solves the problem of expanding the range of metal-polymer compositions processed by molding and sintering into cast iron billets while reducing the processing cycle.

The technical result of the claimed invention is to shorten the technological cycle of manufacturing products.

The technical result is achieved by the fact that the metal-polymer composition for the manufacture of cast iron billets, obtained by mechanical mixing of finely divided iron powder with the components of a mixture of thermoset phenol-formaldehyde resin and plasticizer, has a novelty in that the composition additionally contains iron oxide powder, and salt is used as a plasticizer stearic acid in the following ratio of components, wt.%:

thermosetting phenol-formaldehyde resin 15-20 stearic acid salt 0.4-1.5 iron oxide (III) 0.2-32 iron powder rest.

To obtain billets from alloyed iron, a metal-polymer composition is used, obtained by mechanical mixing of two mixtures, the components of one of which are highly dispersed powders of at least one alloying element and iron, and the components of the second are thermosetting phenol-formaldehyde resin and plasticizer with the same ratio of wt.%; in this case, as a doping element in the first mixture, fine powder of nickel, chromium, copper, molybdenum, manganese, aluminum, titanium, vanadium, silicon is used.

No analogues are known from the prior art having an identical set of features.

The inventive material is obtained by mechanical mixing of an aqueous or alcohol solution of a thermosetting phenol-formaldehyde resin, a plasticizer (stearic acid salt), iron oxide powders and finely divided iron powder, and in the case of production of alloyed cast iron blanks, a pre-prepared mechanical mixture of finely divided iron powders and at least one alloying element. Then the material is dried and granulated. To obtain preforms, the material is formed by loading the mixture into a hot mold and subsequent direct compression at t = 130-150 ° C, by injection molding or injection molding, and the formed preforms are then sintered. At the first low-temperature stage of sintering to 750 ° C, the binder is removed by thermal decomposition, and at the second high-temperature stage at t = 1050 ÷ 1200 ° C, the final sintering is performed to a density close to theoretical; in this case, at the first stage, the thermal decomposition of the resin occurs with the release of active carbon, which, interacting with the oxides, reduces them to iron; the initial iron powder, reduced iron and carbon form a framework strong enough to withstand the destruction under the pressure of the gases formed, as well as under the influence of vibration and its own weight, which makes it possible to decompose the binder without destroying the compact. At the second stage, when heated to the temperature of final sintering and isothermal aging, the final oxidation of excess carbon and reduction of iron oxide takes place, as well as the alloying elements are dissolved in cast iron (if added) and the material is compacted to values of 0.95 ÷ 0.97 of the theoretical density . The number of alloying elements is set according to their percentage in the manufactured cast iron grade. The limits of phenol-formaldehyde resin content were established experimentally in order to provide the sintered material at the low-temperature stage with an excess carbon content, in this case, after sintering, its content should be 2 ÷ 5%. The maximum oxide content is determined based on the need for oxidation of carbon formed in an amount corresponding to the maximum resin content so that the composition of the material after sintering on carbon corresponds to cast iron. On the other hand, the upper limit of the content of iron oxide from the point of view of economic feasibility should be the maximum possible, because dispersed oxide is more economical than dispersed iron and the higher its content, the lower the cost of the composition.

The lower limit of the content of iron oxide is set in accordance with the natural content of iron oxide in the annealed carbonyl iron powder.

As the oxides, both iron (III) oxide with the formula Fe ₂ O ₃ and iron oxide (II, III) with the formula Fe ₃ O _{4 can be used} . Salts of stearic acid can be used as a plasticizer: zinc stearate, calcium stearate, magnesium stearate, etc. The limits of the content of salts of stearic acid are determined by the fact that with smaller amounts there is no significant effect on the fluidity of the mixture, and at higher values compared with the claimed macrodefects on products in the form of blisters and cracks.

Example 1. Were made prototypes of the compositions to obtain cast iron billets with boundary values of the number of components (table 1, a mixture of No. 1 and No. 2).

Table 1 No. p / p Components The content of components, wt.% Mix No. 1 Mix No. 2 Mix No. 3 one Phenol formaldehyde resin fifteen twenty twenty 2 Plasticizer (Zinc Stearate) Zn (C ₁₈ H ₃₅ O ₂ ) ₂ 0.4 1,5 1,5 3 Iron oxide (III) 0.2 32 32 four Fine Iron Powder 84,4 46.5 45,082 5 Carbonyl nickel powder - - 1,418

Example 2. For the manufacture of prototypes of the compositions for producing billets of alloy cast iron, as (mixture No. 3) of the 4th component, a mixture of highly dispersed powders of iron and nickel was used, with a nickel content of 1.418 (wt.%) By weight of the composition, which provides the estimated percentage of nickel in the finished alloy after final sintering in an amount of 2 wt.%.

The calculation of the percentage of an alloying element, for example Nickel, in the composition and in the finished alloy is as follows.

Let x · 100 -% - the nickel content in the finished alloy;

y · 100 -% - the nickel content in the composition. Then from 100 g of the composition after the destruction of the binder and final sintering, (69.482 + y · 100) cast iron is obtained, which includes: 2 g of carbon, (y · 100) g of nickel; (45.082 + 22.4) = 67.482 g of total iron in the free and bound state; the percentage of Nickel in the finished alloy is:

the percentage of Nickel in the composition will be:

With a value of y · 100 = 1.418%, a value of x · 100 = 2%.

Similarly, the number of powders of other alloying elements is calculated, which are introduced into the composition at a given amount in the composition of the finally sintered material.

After removing the binder, the experimental samples were sintered in a neutral medium at t = 1150 ° C.

Table 2 shows data on the carbon and nickel contents, the presence of unreduced oxides in the structure of the material after sintering, and its relative density.

table 2 Mix No. Carbon content (wt.%) Nickel content (wt.%) The presence of oxides Relative density one 4.2-5.0 - No 0.96 2 1.96-2.06 - No 0.95 3 1.95-2.05 2.0 No 0.97

As follows from table 2, the carbon content in the sintered cast iron products corresponds to the boundary values of the carbon content in cast iron. Nickel alloyed cast iron was obtained from mixture No. 3, the content of which is as calculated.

Thus, patentable boundaries for the content of components should be considered reasonable.

Information sources

1. Natanson E.M., Bryk M.T. Metal-polymer materials and products, M., 1979.

2. Tolmassky N.S. High frequency magnetic materials. M .: Energy, 1968, 72 p.

3. Godin Alexander et al. Development and testing of MIM feedstocks based on carbonyl iron powder and a wax-polymer binder system. In the collection of works of the scientific and practical seminar “New materials and products from metal powders. Technology. Production. Application (TPP-PM2005). June 21-24, 2005 ”, Yoshkar-Ola, pp. 33-35.

4. Graboi IE, Thom A. BASF Catamold® materials for powder injection molding. In the collection of works of the scientific and practical seminar “New materials and products from metal powders. Technology. Production. Application (TPP-PM2005). June 21-24, 2005 ”, Yoshkar-Ola, pp. 37-40.

5. Dovydenkov V. A., Krys M. A. Kinetics of binder removal from metal-polymer compositions based on carbonyl powders and phenol-formaldehyde resin. R.sb. Metallurgy. Engineering. Machine tool. Proceedings of the international scientific and technical conference, Rostov-on-Don, September 6-8, 2006, p. 2: 110-112.

Claims (2)

1. The metal-polymer composition for the manufacture of cast iron billets, obtained by mechanical mixing of finely divided iron powder with a mixture of thermosetting phenol-formaldehyde resin and plasticizer, characterized in that it additionally contains iron oxide powder, and stearic acid salt is used as a plasticizer in the following ratio of components, wt. %: thermosetting phenol-formaldehyde resin 15-20 stearic acid salt 0.4-1.5 iron oxide (III) 0.2-32 iron powder rest 2. The metal-polymer composition for the manufacture of cast iron billets according to claim 1, characterized in that it further comprises a fine powder of at least one of the alloying elements: nickel, chromium, copper, molybdenum, manganese, aluminum, titanium, vanadium, silicon, pre-mixed with finely divided iron powder.