CS257476B1 - A method of producing heat treatable steel powder parts - Google Patents

Abstract

The subject of the solution is the production of heat-treatable components from steel powders, including the processing of chips generated during chip-forming machining of metals, containing in mass concentration 0.2 to 1.2% manganese, 0.4 to 1.7% chromium, 0.03 to 0.7% silicon, 0.7 to 1.5% carbon and the remainder, excluding impurities, iron. This method consists of crushing the chips into a powder having an oxygen concentration of 0.5 to 2% by weight, annealing this powder with the addition of 0.5 to 3% by weight of iron oxide in an atmosphere with a predominant proportion of hydrogen or nitrogen at a temperature of 700 to 1,100 °C, pressing the components from the powder with the addition of graphite, sintering the components at a temperature of 1,100 to 1,350 °C in an atmosphere containing completely or predominantly hydrogen or nitrogen and compacting the sintered components under heat, preferably by forging, rolling or overextrusion.

Description

257476

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for the manufacture of heat treatable steel powder components, which is preferably used for the production of powder and metal powder grades thereof.

The powders for the production of components to be heat treated preferably also contain elements such as manganese, chromium and silicon, and always carbon. It is sought to process the powder which would be used for the production of heat-treatable components of the powder-coated non-metallurgy and chips produced by the chip processing of cast steels for heat treatment.

The only drawback of the prior art from the known methods of preparing powders, suitable for the manufacture of components by powder metallurgy processes from various wastes resulting from the processing of cast steels or cast iron, since no one is yet introduced to produce components that fail to reduce the oxygen concentration necessary annealing the powder to a value of less than about 1000 ppm, preferably 500 ppm, and a carbon concentration of less than 0.1%. Low carbon concentration is necessary to achieve good compressibility of the powder and good strength in the non-sintered state needed for further handling. For example, by pressing the pressure of 589 MPa, a compacted density of 6.4 to 6.7 g.cm should be achieved, thus improving the normal compressibility of other powders. A low oxygen concentration is already required in the powder because oxygen is bound bound by elements such as manganese, chromium and silicon and their oxides are easily reducible. Their presence in the burnt sintered and densified component deteriorates in particular the toughness properties. To date, it has been carried out in atmospheres containing predominantly hydrogen or endothermic gas, thus reducing atmospheres. The decarburization of the individual particles is uneven. The smaller ones are sometimes full-blown and only partial.

The above mentioned drawbacks are eliminated according to the invention by a process for the production of heat-treatable steel powder components, including the production of steel powder from chips, produced by the machining of cast steels, the powder annealing, the pressing of the parts thereof, the sintering and the heat-compaction, characterized in that the chips arising from the chipping of cast steels, containing by weight 0,7 to 1,5% carbon, 0,2 to 1,2% manganese, 0,40 to 1,7% chromium, 0,03 to 0,7% silicon and the remainder of the iron, apart from contaminants, is crushed in the state of formation or after hardening by quenching to a powder of predominant size of 0.315 mm, which has 0.5 to 3% oxygen in mass concentration, then iron oxide powder of 0.5 to 4% is powdered weight. This powder mixture is then calcined in an atmosphere containing complete or predominantly hydrogen or nitrogen at a temperature of 700 to 1100 ° C for 0.5 to 8 h. To sieve the powder in an amount sufficient to produce a concentration of carbon in the component after sintering. 0.2 to 1.2% by weight. 2 of this powder blend with conventional lubricant addition components are then sintered at a temperature in the range of 1100 to 1350 ° C for 120 to 15 minutes. in an atmosphere of dew point below -10 ° C containing complete or predominantly hydrogen or nitrogen. Thereafter, the sintered components are hot-compacted, either by pressing, forging, rolling or extruding at a temperature of 650 to 1200 ° C. This produces heat treatable steel powder components.

The main advantage of the production method according to the invention is that it allows the prior art to be processed, e.g. chips after turning, drilling, planing or milling the cast steels of said chemical composition to the desired quality powder. This acosl is a characterisable, and hence necessary, low carbon concentration compared to its concentration in chips and low oxygen concentration.

This makes it possible to squeeze and sintered and compacted under hot conditions the machine parts, which then can be either cemented or refined according to the adductivity or sintering conditions of the bonded carbon concentration in the component.

Claims (4)

3 257476 Particulate Performance Requirements. In this way, it is possible to utilize residual steel chips, on the one hand, to reduce the cost of the powder and thus contribute to a more economically advantageous powder metallurgy technology. The method is also more energy-efficient compared to producing pre-alloyed powders by spraying molten metals, e.g., water. In particular, the method of the invention is possible by the addition of iron oxide powder to the powder by its annealing in an amount which ensures a balance between the oxygen of the oxides and the powder and the carbon in the powder. This allows a rapid reduction of the oxygen and carbon concentration in the powder. The currently reduced iron particles resulting from the reduction of this oxide are added to the powder particles from the chips. This will improve their compressibility, consistency of the compact in the non-caking and sintering of the system. EXAMPLE 1 The chips resulting from the turning of cast iron, containing 1% carbon, 0.3% manganese, 1.5% chromium and 0.3% silicon, were milled in a ball-and-mill mill to form powder. which had an oxygen concentration of 1.5% by weight. Iron oxide powder Fe 2 O 2 was added to the powder at 2% by weight. The powder mixture was annealed in nitrogen at 1050 ° C for 4 h. The powder was calcined at 0.06% and 0.07% carbon, respectively. Zinc stearate was then added to the powder as a lubricant and graphite at 0.4 and 0.8% by weight. From the powder mixture after mixing, the dimensions were 8 x 15 x 78 mm sized 589 MPa rods, which reached a density of 6.55 g.cm 3. The rods were then sintered with hydrogen at 1250 ° C for 30 min and then forged after heating at temperature 150 ° C. In the covariance of the rods, the components had a density of 7.64 g.cm and achieved an additional graft of 0.4% slip of 476 MPa, a breaking strength of 744 MPa, an elongation of 4.1% and a contraction of 10.3% and a graphite of 0.8 %, a yield of 537 MPa, a breaking strength of 757 MPa, an elongation of 3.7% and a contraction of 7.2%. From a steel powder of the same basic chemical composition produced by spraying a pre-alloyed metal melt with water treated with the same procedure for tearing rods, a density of 7.75 g.cm was obtained with an addition of 0.4% by weight of a slip of 335 MPa, strength limit. 549 MPa, 1.3% elongation and 3.3% contraction, and 0.83% graphite, 443 MPa, 544 MPa, 4.1% elongation and 4% contraction. The results show that the turning chips according to the invention produce components having higher strength properties than those of the same chemical composition made by spraying with water. The method can be utilized in the powder metallurgy industry, using, for example, bearing steel strips, as in Example 1, which is a mass source of contamination from other steel grades. The method can be advantageously used for the production of various components such as rolling bearings such as raceways, enclosing rings, floating rings, cages, but also others such as gears, connecting rods, etc. A method for producing heat-treatable steel powder components, comprising producing a steel powder from the chips produced by the casting, chipping, sintering, and hot-compacting of the hot-rolled parts, characterized in that the chips produced by the cast steel machining are containing by weight 0.7 to 1.5% of carbon, 0.2 to 1.2% of manganese, 0.40 to 1.7 1 of chromium, 0.03 to 0.7% of silicon in addition to contaminants and residual iron is crushed to a predominant particle size powder of less than 0.315 mm having an oxygen concentration of 0.5 to 2% by weight, then the powder to which iron oxide powder is added in an amount of 0.5 to 257476 3% by weight is annealed at a temperature of 700 to 1100 ° C for 0.5 to 8 hours in an atmosphere containing complete or predominantly hydrogen or nitrogen, then compressed from the screened powder and the lubricant components sintering at 1100 to 1350 ° C for 15 to 120 minutes in an atmosphere containing complete or predominantly hydrogen or nitrogen dew point below -10 ° C, then sintering the components at a temperature of 650 to 1200 ° C . 2. A method according to claim 1, characterized in that the steel chips are crushed in the state of their formation or after curing, preferably by quenching. 3. Method according to claim 1, characterized in that graphite is added to the annealed powder in such a way that, after sintering, the carbon concentration in the component is obtained in the range of 0.2 to 1.2% by weight. 4. A method according to claim 1, wherein the sintered components are heat-compacted by compression or forging, rolling, extrusion. Severografia, n. P., MOST Price 2,40 Kcs