JPH0480305A - Manufacture of powder high speed steel product - Google Patents

Abstract

PURPOSE:To improve grindability and machinability without lowering mechanical property by making value in the specific range of high temp. heating and parameter at the time of HIP treatment. CONSTITUTION:In the manufacturing method of powder high speed steel product with the hot isostatic pressing (HIP) and forging, to the high speed steed powder containing >=0.01 vol% improving component for machinability, whose shape is varied under hot machining condition, the HIP is executed so as to be in the range of P = (4.0 - 5.6) X 10<4> at the time of using P = T(log t + 37), wherein, T: temp. ( deg.K), t: time (sec) for high temp. heating parameter P at the time of executing the HIP. The heating at higher temp. and for longer time which causes P to exceed the value of P = 5.6 X 10<4> the upper limit value of the high temp. heating parameter P, brings about coarsening of machinable inclusion. In the heating, which does not reach the lower limit value 4.0 X 10<4>, the density after executing the HIP is far from the true density, and even this is forged, the remaining voids are extended and anisotropy is made to high and mechanical property in the product is deteriorated.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention improves grindability without reducing mechanical properties.
This invention relates to a method for manufacturing powdered high-speed steel products with improved machinability. (Prior Art) To manufacture products such as tools from powdered high-speed steel, it often goes through the process of hot isostatic pressing (HIP) - forging - finishing by cutting or grinding. In order to improve the machinability of steel, free-cutting elements such as S and 3e are added, and mainly Mn5 (Se
) measures have been taken to generate inclusions consisting of Such inclusions are finely and uniformly dispersed in the high-speed steel powder obtained by molten metal spraying. However, in the subsequent heating process, inclusions agglomerate inside the powder, and inclusions aggregate and coarsen due to the concentrated S component on the powder surface, and the enlarged inclusions are stretched in the forging process. While increasing anisotropy, hot workability was worsened. For this reason, machinability did not improve as much as expected, and the decrease in mechanical properties led to a decrease in tool performance. In fact, the presence of inclusions with lengths exceeding 1 μIrL is often observed in HIP-forged powder high speed steel products. [Problems to be Solved by the Invention] An object of the present invention is to improve the current state of manufacturing technology for powdered high-speed steel products, to prevent the coarsening of free-cutting inclusions in the heating process, and to reduce the coarsening of free-cutting inclusions in the forging process. Aspect ratio of an object (vertical,
It is an object of the present invention to provide a method for manufacturing a product in which the increase in the lateral ratio (lateral ratio) is suppressed, the mechanical properties are not deteriorated, and the machinability improvement effect can be fully enjoyed. [Means for Solving the Problems] The method for manufacturing powdered high-speed steel products of the present invention is a method for manufacturing powdered high-speed steel products by hot isostatic pressing (HIP>) and forging, wherein A high-speed steel powder containing 0°01 volume % or more of machinability-improving components that change its shape is heated at high temperature during HIP by setting the heating parameter P to P=T (lop t+37> (where T is temperature (°K), When t is time (sec), HIP is performed in the range of P = (4,0 to 5.6) x 104. Powder high speed steel to which this method can be applied is: In terms of JIS steel type symbols, they are as follows: 5KH51, 52, 53, 55, 56, 58° 59.5
KH2, 3, 4, 10 [Function] As a result of research, the inventors found that in the manufacturing process of powdered high-speed steel products, the agglomeration and coarsening of free-cutting inclusions, especially at the particle interface of the powder, is a substantial problem. Proceeds when heated to a high temperature before reaching the upper true density (99.99% or more);
It was also found that the progress of this coarsening differs depending on the heating conditions. Furthermore, the free-cutting inclusions are relatively large (average particle size is 0).
．． It has been found that when the aspect ratio is 5μ or more), the aspect ratio tends to increase in the subsequent forging process. Therefore, we searched for heating conditions that would prevent the coarsening of the free-machining material centering on the powder particle interface and, therefore, less increase in the 7 spectral ratio after forging.As mentioned above, we found that the high temperature heating parameter P was The present invention was achieved by learning that conditions should be selected so as to fall within the range. High-temperature and/or long-term heating at which the high-temperature heating parameter P exceeds the upper limit of 5.6×104 causes coarsening of free-cutting inclusions. On the other hand, when heating does not reach the lower limit of 4.0X10', the density after HIP is far from the true density (90%).
Even if this is forged, the remaining voids are stretched, increasing the anisotropy and resulting in poor mechanical properties of the product.

【Example】

0.0 S as a free-cutting element was added to rDEX80J powdered high-speed steel for tools having the following alloy composition (weight %, remainder Fe).
Steels with various amounts added in the range of 1 to 1.5% were melted and powdered by a gas atomization method. CSi Mn Cr M. 2.8 0.3 0.3 4.2 6V
W.C. The powder was filled into mild steel cans, sealed under vacuum, and HIPed under different high temperature heating parameters.
The obtained sintered body was divided into A) as-is, B) forging at 1200°C (Kenryusha 10.23), and for each sample, the volume % occupied by free-cutting inclusions and the average aspect ratio (L/T > I looked into it.
This measurement was performed on particles having a size of 0.1 μm or more. After the sample was quenched and tempered, it was ground using a white alundum grindstone, cut using an end mill, and subjected to an impact test, and the following physical properties were measured. Grinding ratio: Grinding amount/Wheelstone wear amount Cutting performance index: The value of NO3 that gave the best result was set to 100
In order to compare the relative value of the transverse rupture force in the lowest direction, experiments were also carried out when the high temperature heating parameter P was outside the range of the present invention. The data are shown in the table below. [Effects of the Invention] By producing a powder high-speed m product by the method of the present invention, it is possible to enjoy the effect of improving machinability while avoiding the deterioration of mechanical properties caused by the addition of free-cutting elements. Patent Applicant Daido Steel Co., Ltd. Agent Patent Attorney Souo Suga Procedural Amendment (Voluntary) IO September 9, 1991

Claims (1)

[Claims] In a method for manufacturing powdered high-speed steel products by hot isostatic pressing (HIP) and forging, a machinability-improving component whose shape changes under hot working conditions is 0.01% by volume. High-speed steel powder containing the above-mentioned high-temperature heating parameter P during HIP is P = T (logt + 37) [where T is temperature (°K) and t is time (sec)], P = (4.0 A manufacturing method characterized in that HIP is performed in the range of ~5.6)×10^4.