CS248508B1 - A method for producing a hardened steel with a subledeburitic matrix - Google Patents

Abstract

The production method is based on the technology of granulation of the molten alloy and subsequent sintering of the granulate. Subledeburitic steel of the basic composition, i.e., without the addition of titanium compounds, is melted and the melt is granulated by one of the known methods. The resulting powder granulate is then, after any preliminary treatment, mixed with the appropriate proportion of titanium powder compounds, pressed and sintered.

Description

(54) A method for producing a quenchable steel with a subledeburitic matrix

The production method is based on the technology of granulating the molten alloy and subsequently sintering the granulate. Sub-base steel, i.e., without the addition of titanium compounds, melts and the melt is granulated by any of the known methods. The resulting powder granulate is then, after optional pretreatment, mixed with an appropriate proportion of the titanium powder compounds, pressed and sintered.

248 508

248 508 (11) (B1) (51) Int. Cl *

OJ C 22 C J8 / 14

This invention also relates to a process for the production of a hardenable steel with a subledeburitic matrix, enriched with a titanium compound, suitable for the production of powerful cutting and non-cutting tools.

The materials used hitherto contain a significant proportion of the tungsten, molybdenum, vanadium, or tungsten carbide carbides, respectively. so-called complex carbides. Some of them are also enriched with titanium carbide or carbonitride. The steel which is the subject of the invention contains, in the state after quenching, in addition to the basic matrix, exclusively titanium compounds, or a small residual amount of ledeburitic carbides of other types. The production of this steel by conventional metallurgical processes, ie from ingots or directly in the form of castings, does not make full use of the advantages that result from its chemical and phase composition. Steel produced in this way has sufficient hardness, but low toughness and difficult to grind.

The above-mentioned disadvantages are overcome by the process for the production of the hardenable steel with the subledeburitic matrix according to the invention comprising from 0.3 to 0.7% by weight, at most 3% by weight of silicon, at most 5% by weight of chromium, at most 2% by weight of vanadium. %, not more than 4% by weight of molybdenum, not more than 10% by weight of cobalt and enriched from 10 to 60% by volume of the titanium compound. The principle of the invention consists in that the base alloy is granulated after melting, after which the powder granulate is mixed with a proportion of the titanium compound and subsequently pressed and sintered.

The process according to the invention is based on the technology of granulating the molten alloy and subsequently sintering the granulate. According to this process, the subledeburitic steel of the basic composition, i.e. without the addition of titanium compounds, is melted and the melt is granulated by any of the known methods, for example by spraying with neutral gas, water and the like. The resulting powder granulate is then mixed after optional pretreatment, such as grinding, annealing and the like,

248 508

- 2 with an appropriate proportion of the titanium powder compounds, pressed and sintered. Various powder metallurgy processes already in use in the manufacture of tool materials can be used for stamping and sintering.

The steel produced by the process according to the invention contains particles of titanium compounds in a very dispersed form which guarantees the necessary wear resistance and effectively prevents grain growth when heated to the quenching temperature. The homogeneity and isotropy of the structure ensure sufficient toughness and favorable mechanical properties even for single-sided rod blanks ·

Example 1

A base alloy having a carbon content of> 5% by weight manganese 0.4% by weight silicon 0.3% by weight chromium 4% by weight tungsten 3.5% by weight molybdenum 2% by weight is granulated by a stream of nitrogen after melting. After treatment, the granulate is mixed with titanium carbide in a ratio of 70:30 by volume. The resulting mixture is homogenized and pressed into blanks, tools or functional elements such as cutting inserts. The moldings are then sintered at a temperature of 1200 to 1250 ° C.

Example 2

Base alloy of carbon 0,4% manganese 0,4% silicon 1,8% chromium 4,5% tungsten 1,4% molybdenum 3,5% vanadium 0,8% cobalt 8% is granulated with water after melting. The granulate is mechanically adjusted to

248 508 an average particle size of about 10 µm, anneals at 900 to 95 ° C under a vacuum of 10 pa 3pa and, if necessary, dopes with carbon (for example in the form of carbon black). They are then mixed with 60:40 parts by volume with titanium carbide. After homogenization, the products are pressed with a pressure of about 500 MPa, which are then sintered at a temperature of 1,150 to 1,250 C.

The process according to the invention can be used for the production of semi-finished and finished products, in particular tools and functional elements. The steel produced by the proposed method is suitable for the production of the most stressed cutting tools, it can also be used for cutting tools if they require extra compressive strength and / or wear resistance.

Claims (1)

SUBJECT OF THE INVENTION A process for producing a hardenable steel with a subledeburitic matrix, containing from 0.3 to 0.7% by weight of carbon, at most 3% by weight of silicon, at most 5% by weight of chromium, at most 2% by weight of vanadium, from 1 to 9% by weight of tungsten, % by weight of molybdenum, not more than 10% by weight of cobalt and enriched from 10 to 60% by volume of the titanium compound, characterized in that the base alloy is granulated after melting, after which the powder granulate is mixed with a proportion of the titanium compound and subsequently pressed and sintered.