JPS5873703A - Production of powder metal forged parts having excellent hardenability and toughness - Google Patents

Abstract

PURPOSE:To produce powder metal forged parts having excellent hardenability and toughness in the stage of producing the powder metal forged parts by using the Cr-Mn low alloy steel powder of ultra low oxygen produced by an oil spraying method for the raw material, subjecting green compacts to a water infiltration treatmnt and decarburizing the green compacts in the stage of sintering. CONSTITUTION:The melt of inexpensive Cr-Mn alloy steel having excellent hardenability is pulverized by an oil spraying method using nonpolar solvents or mineral oils, vegetable oils, etc. The powder is degreased and in that state the powder is molded under pressure without decarburizing and annealing to produce green compacts. The green compacts are subjected repeatedly to water infiltration and drying to control the content of oxygen up to the content necessary for decarburization. Thereafter the green compacts are heated and sintered in an inert gaseous atmosphere, and are then decarburized at the oxygen content controlled in said sintering stage; thereafter the temp. is reduced down to the forging temp. at which the green compacts are forged. The powder metal forged parts having excellent hardenability and toughness are produced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides Ct-M produced by an oil spraying method using a non-polar solvent, mineral oil, or animal and vegetable oil as a spraying medium, and subjected to decarburization and annealing treatment. This invention relates to a 4° method for manufacturing powder forged products with excellent hardenability and toughness using FI-based low alloy steel powder as a raw material.

As a raw material for powder forging, water spray powder is considered to be optimal for both iron powder and alloy steel powder in terms of performance and price. and,
Hardenability and price are issues for alloy steel powder used in parts with strict quality requirements.

Regarding hardenability, for example, when targeting passenger car parts, Ns-Mo (460G), which has been conventionally used, is used.
Steel powder is in short supply. Therefore, it is essential to use an alloy powder containing Cr%M4, and replacing it with Cr% glue is also effective in lowering the price.

However, Cr and MH are more easily oxidized than N1 and MQ when water is sprayed, and since the formed oxides are relatively inexpensive, they are difficult to reduce and have a high oxygen content. This oxide deteriorates the toughness of powder forged products as non-metallic inclusions.

It is difficult to reduce the oxygen cap in Cr-M and copper powder at the powder stage. be.

However, even if a high sintering temperature is used, a large amount of oxide remains, reducing the toughness of the forged product and having a negative effect on the hardenability. According to experiments, the oxygen content is 0.02
If the impact value exceeds -, the impact value decreases significantly, but powder forged products produced by the conventional water spray method contain a large amount of at least 0.3- or more.

Therefore, we aimed to have good quenched toughness at least as good as rolled steel and a low price (Y-Mfi copper powder has various problems with the current manufacturing method, and although mass production technology has been established, it is round.

In view of the current situation, this invention was invented by the applicant earlier and is manufactured by the 9-oil spraying method, and only undergoes degreasing treatment without decarburization or annealing treatment. This issue proposes a manufacturing method for powder forged products that uses copper powder as a raw material, performs water immersion treatment to reduce the amount of oxygen required for decarburization, and performs decarburization during sintering, which can significantly reduce manufacturing costs.゛It's something.

In other words, in this invention, molten metal is pulverized by an oil spraying method using a non-polar solvent, mineral oil, or animal and vegetable oil as a spraying medium, and then only degreased and matured coral is used. A green compact obtained by compression molding CR-M series low alloy steel powder is subjected to water immersion treatment with hot water etc. to adjust the oxygen content to the required tKli for decarburization, and then heated to the sintering temperature. The purpose is to sinter the product, decarburize it during the sintering process, and then hot forge it to produce a nine-powder forged product with excellent hardenability and individuality.

The raw material of this invention is ultra-low oxygen alloy steel made by oil spraying, and oxides present in the steel can be easily reduced, so sintering can be carried out by holding it at 1200"C for 15 to 30 minutes. As the sintering protective atmosphere gas, it is possible to use a mixed gas of an inert gas and a reducing gas, ammonia decomposition gas, propane gas, or hubtan converted gas.

In addition, since the raw material has not been decarburized, it contains medium carbon1, and this invention involves repeating water immersion and drying before sintering.
The amount of acid contained in the pot is adjusted to the amount required for decarburization by so-called water immersion treatment. During the sintering process, decarburization is carried out using the oxygen contained in the material.

Sintering of the green compact is carried out at 1200° C. in an inert gas atmosphere mainly composed of nitrogen gas, and after brining, the temperature is lowered to a normal forging temperature, and the temperature is kept soaked for hot forging.

In this invention, the undecarburized powder compact is decarburized in the sintering process after adjusting the oxygen content, so there is no need to add oxides etc. for the decarburization process. By mixing decarburized powder with the same composition as the raw material, which has the same composition as ultra-low carbon by decarburizing carbon, it becomes easy to adjust the carbon in the steel.

Next, embodiments of the invention will be described.

C0.60%, Mn 0.75%, Cr 1.01G
, Mo O, 24, 0.0.05 (the remainder substantially we
steel powder by oil spray consisting of 70- and C0,05'll
, MnO, 751, Cr 1.0111%Mo 0.
A raw material prepared by adding a small amount of zinc stearate as a lubricant to a mixed powder of 3G1g of decarburized powder consisting of 23'l, 0.0.05-1 and the remainder substantially F. was cold-rolled by applying a force of 6t/-. After compressing to produce a green compact with a density of 5.8 fb'cc and adjusting oxygen by repeatedly immersing it in water and drying it, 511 i
The sample was sintered by holding it in a sintering furnace K at 1200° C. for 30 minutes in an inert gas atmosphere of −951 N. And 1000”
When it descended to C, it was hot forged to make a powder forged product. The final product obtained had a CO of 0.26 m, 0.0.01 inch, and a density of 7-851'/cc.

Applicant: Sumitomo Metal Industries, Ltd. Continuation of page 1 0 shots: Masaru Nishiguchi 1-3 Nishinagasu Hondori, Amagasaki City Sumitomo Metal Industries, Ltd. Central Technology Inside the research institute

Claims (1)

[Claims] The molten metal is made into a powder by an oil spraying method using a non-polar solvent, mineral oil, or animal and vegetable oil as a spraying medium, and then only degreased and compression molded into undecarburized Ct-Mm low alloy steel powder. After applying water immersion treatment to the obtained nine compacted powder using hot water etc. to adjust the amount of oxygen content to the amount required for decarburization,
A method for producing a powder forged product with excellent hardenability and toughness, characterized by heating to a sintering temperature and sintering, decarburizing in this sintering process, and then hot forging.