Method of tool steel properties improvement

FIELD: mechanical engineering; aircraft industry; shipbuilding; methods of metal forming.

SUBSTANCE: the invention is dealt with the methods of metal forming intended to increase durability of tool steels and may be applied in the field of mechanical engineering, aircraft industry, shipbuilding and other industries. The substance of the offered invention consists in plastic deformation of billets blanks out of a tool steel by a compression setting with a twisting till the accumulated deformation defined by the formula:

where - the critical deformation causing an intensive growth of grains of a microstructure of the steel; and - additional optimal deformations of compression and shift ensuring the maximum increase of the steel wear resistance. Application of the given invention in an industry will allow to increase rather efficiently the steel wear resistance of the steel, that may be used for production of cutting and measuring tools.

EFFECT: the invention ensures the maximum increase of wear resistance of the steel, that may be used for production of cutting and measuring tools.

 

The invention relates to the processing of metals by pressure applied to the hardening of tool steels and can be used in aircraft construction, shipbuilding and other industries.

The known method [1] to improve the properties of the billet of tool steel, including plastic deformation of the workpiece draft to the relative deformation, equal to the sum of the critical strain, resulting in the subsequent heat treatment intensive grain growth microstructure of steel and is determined empirically optimal incremental deformation, providing the greatest resistance of steel.

The disadvantage of this method is the limited possibility to increase the resistance of tool steel, only due to the plastic deformation of precipitation.

The invention is directed to providing a higher degree of increasing the resistance of tool steels by combining deformation precipitation and shear strain in the process.

This is achieved by the fact that the billet of tool steel is subjected simultaneously with a draft of the torsion to the accumulated strain equal to

where ekrcritical accumulated strain, resulting in the subsequent heat treatment intensive grain growth microstructure of steel, and the self is haunted by lowering the resistance of the latter; Δfwiththat Δγ - defined empirically optimal incremental logarithmic strain compression and shear deformation, providing a higher degree of increasing the resistance of steel.

The essence of the method consists in the following. The manufacture of rods of tool steel billet is subjected simultaneously with plastic draught torsion to accumulated strain E.

In the complex loading to which it relates and sludge, torsion, deformation theory of plasticity appreciate the value of accumulated deformation (or rate of deformation) that is

In the present invention the accumulated deformation e is determined by the formula

Here

logarithmic strain compression, where h0h - respectively the source and the current height of the workpiece;

the shear deformation at the point of the cross-section of the workpiece radius ρvarying in the range of 0≤ρ≤r ϕ - the absolute angle of rotation of the end sections of the workpiece relative to each other; r is the current radius of the workpiece defined by the formula

where r0is the initial radius of the workpiece.

The present invention dostat is a rule can be effectively used to increase the stability of the instruments cylindrical type reamers, end and cylindrical cutters, countersinks. These types of tool cutting edges are located on a cylindrical surface. In this regard, to assess the deformed condition by the formula (3) you have to shear deformation to determine when ρ=r, ie,

Critical accumulated strain in the formula (1) is also determined according to relation (2), from which it follows that

wherethat γ0accordingly critical logarithmic strain compression and shear deformation, defined respectively by the formulas (3) and (4). According to the same formulas also define and Δfwithand Δγratio of (1).

According to the formula (1) pre-determine the critical accumulated strain (ekr), and then by extension the optimal deformation of the compression and shear Δfwithand Δγproviding a higher degree of increase of the resistance of steel. Further deformed billet is subjected to thermal hardening and subsequent tempering at the appropriate for each tool steel temperature mode.

An example implementation of the proposed method considered at low-alloy tool steel 9ÕÑ.

From the mentioned steel rods were manufactured by zagotavlivaetsya d 0=15 mm and a height of h0=25 mm, After which the workpiece before heat treatment were subjected to upsetting twist to accumulated strain E.=0,1; 0,2; 0,3; 0,35; 0,45; 0,50; 0,55; 0,6. The deformation of the workpieces held in a specially designed and manufactured stamp, allowing time to settle and twist. The design of this stamp is presented in [2].

To determine the critical accumulated strain of the part of the plastically deformed workpiece after heat treatment were microsections for estimating the grain size of the microstructure of the investigated steel. The result of statistical processing of experimental data determined that the critical accumulated strain ekrfor steel 9ÕÑ was 0,107(; γ0=0,132).

To establish the effect of increasing the resistance of steel were conducted stoimostnye tests made of the deformed billet cutters with appropriate heat treatment (hardening and subsequent tempering).

Tests incisors showed that the resistance of steel depends on the accumulated strain. Moreover to strain e=ekrthere is a reduction of resistance of steel (almost 29%) compared to the non-deformed plastically steel.

When deformation e>fkris monotone increasing the resistance of steel. The largest is ysenia, almost 2.4 times (by way of a prototype 1.8 times) the resistance of steel relative to the resistance of the processed according to the traditional technology (without plastic processing blanks), occurs when accumulated strain e=0,43 and, accordingly, the optimal values of Δfwith=0,20, Δγ=0,339. Increase resistance on resistance on the way the prototype was 1.33 times (33%)which was significant for cutting tools. Temperature heat treatment in the comparable methods were identical.

The use of the invention in industry will effectively increase the resistance of tools (cutting and measuring).

SOURCES of INFORMATION

1. RF patent №2215795, C 21 D 8/00, 7/00. 10.11.03. Bull. No. 31.

2. RF patent №2109264, G 01 N 3/08, 20.04. 1998, bull. No. 11.

Method for improving properties of a workpiece tool steel, including plastic deformation of the workpiece draft up the necessary degree of deformation and subsequent heat treatment, characterized in that simultaneously with the draft of the workpiece is subjected to torsion to accumulated strain, the value of which is calculated by the formula

where ekrcritical accumulated strain, resulting in the subsequent heat treatment intensive growth of grains m is crostructure steel; Δfcand Δγ - defined empirically optimal incremental accordingly logarithmic strain compression and shear deformation, providing a higher degree of increasing the resistance of steel.



 

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