CS200331B1 - Method of direct production of the sintered nonalloyed iron pressings and bands from the ferric oxide - Google Patents

Description

Method of average production of sintered Delegated and alloyed iron extrusions and strips of iron oxides

The invention 3a relates to a method for the direct production of unalloyed and alloyed iron extrusions and strips by the use of finished iron powder, which solves the problem of compressibility, increasing the reduction activity! and the removal of the desired admixtures in the moldings according to the individual types of iron oxides, and a method for preparing iron oxides and their alloying for processing into non-sintered preforms, wherein under prescribed conditions the preforms in a further reduced sinter are intended to produce machine parts or belts by powder metallurgy.

For the production of sintered iron compacts 3a it uses powdered iron, which until now with the addition of a lubricant and, in the case of carbon or alloy steel, also with the addition of graphite and corresponding powder alloys, unless partially or completely pre-alloyed powdered metals are usually cold pressed in closed dies, which have predominantly the final shape and dimensions of the machined component, to a density which is a certain condition for achieving the desired properties of the molded part by its production process. The compacts after sintering are sintered at appropriate temperatures in protective, mainly reducing atmospheres. After sintering, such products are either directly used as finished machinery or are calibrated or double molded and sintered or used as preforms for forging or as extrusion extrusions on the basis of the intended use and achievable performance, and these operations can also be performed directly from the sintering process. temperature with the heating of swordfish. Iron powder or steel powder can also be pressed directly

200 331 per strip and by repeated sintering and re-rolling a strip of desired dimensions and properties is produced.

Iron powder, which is the main constituent material in the manufacture of sintered iron-based machinery, and is produced predominantly by (a) reduction of iron oxides, the end product of which is sponge iron, the most widespread worldwide, (b) spraying iron or steel melt into air; inert gases or water.

To a small extent, mechanical powdered iron is also produced by grinding wire pieces in a special mill. For the production of sponge iron, mainly natural ore concentrates are used, which have a high chemical purity, while the actual reduction of iron oxides to sponge iron is done mainly by a solid reducing agent, coke with the addition of lime in retorts in tunnel furnaces. In this way, the scaling produced by hot rolling of low carbon steels is also processed. It is also known to produce sponge iron powder by reducing the scales by using a combined, gaseous and solid reducing agent. Since the sponge-like types of powdered iron in the initial state and the sprayed-on types of powdered iron in the initial state are predominantly undesirably high in oxygen and carbon, all such types of powdered iron must be subsequently mechanically and thermally treated to achieve the necessary physical and chemical properties for their application for production of sintered machine parts with high technical parameters. The production of iron powder of any kind, of which a part with lower quality requirements is also used for welding electrodes and for other purposes, always entails considerable investment and constructional and mechanical costs, as well as other processing costs. Accordingly, the cost of material in the manufacture of baked-on machine parts is largely influenced by the inevitable cost of producing iron powder.

In an effort to exclude this costly production of iron powder from the process of producing fusible iron-based machine parts, the literature describes a straightforward process for making fusible preforms intended for metalworking from rich natural iron ores. In this process, in order to compress the ore powder into the shape of the desired moldings, it is recommended to add to the ground treated ore concentrate as a binder a cellulose-based adhesive, eg wallpaper adhesive and to reduce it as a petroleum coke. The mixing of these components results in a pasty mass which is compressed in molding tools, which are then reduced in furnaces by a predominantly and neutral gas atmosphere at a temperature of at least 1150 ° C for not less than 4 hours. The preforms produced in this way are still present after the reduction of either the residues of the unreduced iron oxides or the residues of the reducing agent, which is also common in the production of reduced sponge-like types of powdered iron, which must therefore be additionally reduced.

The disadvantage of the previous production of baked machine parts is mainly the necessity to use powdered iron produced by special processes, which substantially increases the requirements for technical and investment equipment of the whole production as well as costs for production of baked machine parts and their price. Any lack of production capacity for the production of powdered iron adversely affects the entire production of sintered machine parts, or

200 331 increase the requirements for imports of iron powder. The disadvantage of said straightforward prooess for the production of sintered preforms is, in particular, that it is based solely on the use of natural high purity ore concentrates, thereby limiting its applicability in particular to areas where such pure ores are present. A serious disadvantage of this process is that naturally iron oxides are relatively difficult to reduce, so high reduction temperatures and long times are necessary to achieve the desired degree of reduction. A disadvantage of this process is also that only a solid reducer is used as the reducing agent, which must then be added to the iron oxides in a greater than stoichiometric ratio, which leads to problems with precise control of the whole reduction process and ultimately resulting in unreduced residues. iron oxide, either to the remainder of the reducer in the moldings, which is usually always the cause of the deterioration of the mechanical and, in particular, toughness properties of the machine parts produced by the process. Another drawback of this process is also that as a bonding agent to ensure the coherence of the compacts, it only uses a liquid adhesive which forms a paste-like mass with iron oxides, making it difficult to process these iron oxides into compacts in conventional tools and equipment where only in powder form. We also consider the disadvantage of the straightforward process that it currently creates certain conditions only for the production of non-alloy forged hot forgings.

The aforementioned disadvantages do not have the direct production of sintered unalloyed and alloyed iron extrusions and strips according to the invention, which is based on the fact that the iron oxides which arise during regeneration of exhausted pickling baths after pickling steel with hydrochloric or sulfuric acid or a mixture of natural iron oxides or iron oxide scraps resulting from the total regeneration of depleted pickling baths after hydrochloric acid pickling of the steels, a solid reducing agent in powder form is added in an amount of 2 to 10% by weight or 20 to 30% by weight based on the amount of iron oxide; up to 10% by weight, based on the amount of iron oxide, binder, preferably methylcellulose or sucrose, in an amount of 2 to 8% by weight, based on the amount of iron oxide and optionally alloying elements in the required amount in powder form, then the mixture is processed to moldings by pressing or rolling into strips which are then reductively sintered in a reducing gas or an inert atmosphere at a temperature lower than 1100 ° C for less than 3 h.

For the method for the direct production of sintered unalloyed and alloyed iron extrusions and strips according to the invention, iron oxide produced by the total regeneration of depleted pickling baths after the pickling of steels with hydrochloric acid resulting from the decomposition of ferrous chloride at a temperature below 500 ° C is used as iron oxide. the bulk density of which is then in the range of 0.5 to 0.7 g.cm < 2 > ^The particle size is less than 0.1 mm and has a bulk density of less than 2.5 g ^/ cm @ 2. Natural iron oxides or scales having a particle size below 0.1 mm can also be successfully used in the process according to the invention if 5 to 20% by weight of iron oxides are added thereto, resulting from the overall regeneration of exhausted pickling baths after pickling. steels with hydrochloric acid having a bulk density in the range of 0.5 to 0.7 g.cm < -1 > or even ferric oxide formed by the decomposition of ferrous sulfate heptahydrate. The advantages of the process according to the invention are also achieved if a solid reducing agent in an amount of 2 to 10% by weight is added to the iron oxides to accelerate the reduction process, using graphite, carbon black or petroleum coke as reducing agent and then sintering or strip sintering. It is carried out in a gaseous reducing atmosphere or when a solid reducing agent is added in an amount of 20 to 30% by weight, and then the reducing sintering is then carried out in a gaseous inert atmosphere. To accelerate the sintering process and to increase the bulk density of the powder mixture, iron powder is also added to the iron oxides in an amount of 2 to 10% by weight. For the production of sintered alloy moldings and strips according to the invention, the alloys are added to the iron oxides in the form of the respective powdered metals, or in the form of powdered ferroalloys, or in the form of oxide-alloying elements reducible at selected reducing or lower temperatures, or in the form of non-reducible oxides at the temperatures used to achieve dispersion hardening, such oxide being, for example, alumina or magnesium oxide. To ensure the coherence of iron oxides and other additives when molding as a binder, 2 to 6% by weight of methylcellulose powder, sachet or cellulose or sulphite leach adhesive are added in the powder or paste mixture after mixing and cold pressed in closed dies pressings of 200 to 600 MPa or the strip is rolled from it.

Example 1

5% by weight of methylcellulose powder is added as a binder to iron oxide having a bulk density of 0.5 g.cm ^< 2 > and a particle size of less than 40.

From this powder mixture after mixing, 13 mm diameter cylinders 11 mm in height are pressed in a compression die at a pressure of 192 MPa, which are then sintered at 1 ° C for 1 h in split ammonia, then compacted to freeze the dimensions in a die with a diameter of about 10% less by a pressure of 589 KPa and finally sintered at 1050 ° C for 2.5 h in split ammonia. After this treatment, the rollers reached a density of 7.15 g ^/ cm @ 2 and a hardness of 85 HV10.

Tear-rod samples pressed from said iron oxide / binder powder mixture at a pressure of 392 MPa, followed by a reduction sintering at 1095 ° C for 1 h in split ammonia, after a compression pressure of 589 MPa and a sintering at 1050 ° C for 2.5 h in cleaved ammonia reached a density of 6.4 g.cm ^{- 1} , a breaking strength of 160 MPa, an elongation of 5% and a hardness of 73 HV 10.

Example 2

To a ferric oxide having a bulk density of 0.5 g.cm < 2 > and a particle size of less than 40 [mu] m resulting from the overall regeneration of exhausted pickling baths after hydrochloric acid pickling is added 25% by weight graphite and 5% powdered methyl2CC cellulose based on both additives. amount of ferric oxide.

From this powder mixture after mixing, tear-rod samples are pressed in a compression die at a pressure of 294 MPa, which are then sintered at a temperature of 950 ° C for 1 h under nitrogen, then squeezed at 589 MPa in the die, considering shrinkage. sinter at 1100 ° C for 2 h in split ammonia. The treated samples reach a density of 6.2 g.cm ^-3 , a yield strength of 180 MPa, an elongation of 5.3% and a hardness of 79 HV 10.

Samples prepared from said powder mixture after the same reduction sinter treatment were hot forged by precipitation with a 50% reduction in sample height after heating at 1100 ° C for 15 min. under a powder of graphite under a nitrogen atmosphere and then sintered at 1100 ° C for 2 h in split ammonia. After this treatment, the samples reached a density of 6.2 g.cm ^-3 , a strength limit of 275 LPa, an elongation of 1.3% and a hardness of 100 HV 10 at a carbon content of 0.13%.

Example 3

An iron oxide having a bulk density of 3.1 g.cm &^lt; ³ & gt ^; with a mean particle size of about 500 tim, resulting from the regeneration of exhausted pickling baths after pickling of steels with hydrochloric acid is ground in a suitable mill, most preferably in a vibratory mill typically have a bulk density of 1.5 g.cm ^-3 . After the iron oxide having a particle size below IC50 of 10, 10% by weight of graphite, 15% by weight of iron powder with a particle size of less than 100% and 5% by weight of methylcellulose powder are added based on all additives to the amount of iron oxide.

After mixing, tear-rod samples are pressed from this powder mixture at a pressure of 589 MPa, which is then sintered at 1095 ° C for 1 h in split ammonia, pressed at 539 MPa, and sintered again at 1100 ° C for 2 h at split ammonia. After such processing, the bars reach a density of 7.2 g.cm * ³ , between a strength of 260 MPa, an elongation of 8.1 $ and a hardness of 91 HV 10.

Samples prepared from said powder mixture in the same manner were forged in a post-sintering state by precipitation with a 50% reduction in height after heating at 1100 ° C for 15 min. in a bed of graphite under a nitrogen atmosphere and then sintered at 1100 ° C for 2 h in split ammonia. After this treatment the sample reaches a density of 7.4 g.cm ^-3 , a strength of 258 MPa, an elongation of 3.3% ε and a hardness of 92 HV 10.

Example 4

To a powder mixture consisting of ferric oxide according to Example 3.10% graphite and 10% iron powder, 5% by weight of media and 5% by weight of nickel based on the iron content of the mixture and 5% by weight of methylcellulose powder are added based on the amount of all components.

After mixing, tear-rod samples are pressed from this mixture at a pressure of 589 MPa, which is then sintered at 1095 ° C for 1 h in split ammonia, then

200,331 are pressurized to 589 KPa and sintered and sintered at 1100 ° C for 2 h in split ammonia. After this treatment, the samples reached a density of 7 g.cm < -1 >, a yield strength of 526 l Pa, an elongation of 4% and a hardness of 207 MPa.

After mixing, tear-rod samples are pressed from said mixture at a pressure of 294 KPa, which are then baked at 1095 ° C for 1 h in split ammonia, then hot-forged by precipitation with a 50% reduction in height after heating at 1100 ° C. for 5 min in a graphite powder under nitrogen atmosphere and sinter at 1100 ° C for 2 h in split ammonia. After this treatment, the samples reached a density of 7.42 g.cm ^-3 , a breaking strength of 680 MPa, a hardening of 3.6% and a hardness of 271 HV 10.

Example 5

To a mixture of ground treated shawls with a particle size of less than 100 μπι with a bulk density of 1,9 g.cm ³ and 10% by weight of ferric oxide resulting from the regeneration of exhausted pickling baths after pickling of steels with hydrochloric acid with a bulk density of 0,5 g.cm " 3 aa> adds 5% by weight of graphite based on the amount of iron oxides and 5% by weight of methylcellulose powder. From this mixture, 10 mm diameter 13 mm rollers are pressed under a pressure of 490 MPa and then sintered at 1095 ° C for 2 h in split ammonia, pressed at 589 MPa and baked again at 1100 ° C for for 2 h in split ammonia. After this treatment, the rollers have a density of 6.8 g.cm < 3 > and a hardness of 78 HV 10.

Spdaob's direct production of sintered unalloyed and alloyed iron compacts according to the invention allows, in addition to achieving the economic benefits mentioned, the elimination of iron oxide residues or solid reducing agents in finished moldings or strips, so that the preforms or preforms produced by this process can be further processed by powder metallurgy or materials with high technical parameters which do not have the same level of performance as the materials produced by the previous processes. The solution according to the invention for introduction into production only requires conventional powder metallurgy equipment for pressing, baking, rolling, extrusion and forging.

Claims (9)

1. A process for the direct production of sintered unalloyed and alloyed Iron Extrusions and strips of iron oxides, characterized in that iron oxides formed during the total regeneration of depleted pickling baths after pickling of steels with hydrochloric or sulfuric acid or the mixing of natural iron oxides or scraps and ferric oxide resulting from the recovery of spent pickling baths after hydrochloric acid pickling of the steels, and and adds a solid reducing agent in an amount of 2 to 10% by weight or in an amount of 20 to 30% by weight, iron powder in an amount of 2 to 10% by weight. In the case of 2 to 8% by weight, based on the amount of all components and, if appropriate, the alloy, in powder form, the resulting mixture is processed into compacts by compression or by strip rolling, which are then sintered in a reduced manner. gaseous reducing or inert atmosphere at 200 331 of less than 1100 ° C for less than 3 h. 2. The process according to claim 1, characterized in that the iron oxide used is the total recovery of the exhausted pickling baths after pickling of the steels with hydrochloric acid resulting from the decomposition of ferrous chloride at a temperature below 500 ° C, the bulk density of which is in the range of 0.5 to 0.7 g.cm ^- or formed by the decomposition of ferrous chloride at a temperature of 800 to 900 ° C, whose bulk density is then in the range of 2.5 to 3.3 g.cm - with a spherical shape After grinding, preferably in a vibratory mill, its particle size is less than 0.1 mm and its bulk density is less than 1.5 g.cm or ferric oxide formed by the decomposition of ferrous sulfate heptahydrate. 3. The process according to claim 1 or 2, characterized in that from 5 to 20% by weight of iron oxide, which is produced by regeneration of exhausted pickling baths after hydrochloric acid treatment by decomposition of hydrochloric acid, is added to natural iron oxides or scales in powder form. Fe (III) at a temperature of less than 500 ° C, the bulk density of which ranges from 0,5 to 0,7 g.cm ^- · ³ . 4. The process of claim 1, wherein a solid reducing agent is added to the iron oxides in an amount of about 10% by weight when the reducing sintering is carried out in a reducing atmosphere, or in an amount of about 30% by weight. the sintering is carried out in an inert gas atmosphere using graphite, carbon black or petroleum coke as reducing agent. 5. A method according to claim 1, wherein iron oxide and reducing agent are added with iron powder ε having a particle size of less than 0.1 mm in an amount of 2 to 10% by weight, based on the amount of iron oxides, 6. Process according to claim 1, characterized in that the alloys are added in the form of respective powdered metals or in the form of powdered ferroalloys or in the form of reducible oxides or in the form of non-reducible oxides for dispersion hardening, which may be for example alumina or magnesium oxide. . 7. The method according to claim 1, 5 or 6, characterized in that methylcellulose powder, sucrose or a cell-based or sulphite-leach adhesive are added as binders. 8. The method according to claim 1 or 7, characterized in that the powder or paste mixture is cold pressed in sealed dies by a pressure of 00 to 600 MPa. 9. The method according to claim 1 or 7, characterized in that a strip is rolled out of the powder or paste mixture.