SU1399073A1 - Method of determining the optimum speeds of cutting - Google Patents

Abstract

The invention relates to metal working, in particular, to determining the optimal cutting speeds when machining steels with a carbide tool with a heated cutting layer, and can be used to designate cutting and heating modes when machining alloy steels and other hard-to-work materials. The purpose of the invention is to simplify by eliminating experiments related to cutting a hot metal, and improving the accuracy of determining the optimum cutting speed during processing with a heated cutting layer. The depth of the cut is taken equal to the size of the zone with a modified structure and use the following relationship to determine the cutting temperature of steel in a cold state Q (Q., -M): K, where Q p is the cutting temperature during processing without heating; Q „„ ductility dip temperature; Mz is the onset temperature of the martensitic transformation (preheating temperature); K is the experimental coefficient taking into account the effect of preheating on the properties of the workpiece, K V N H N, where, J is the dynamic hardness of the workpiece in the heated (initial) state. According to the plot, the cutting temperature is the cutting speed constructed for the machining conditions with a cutting depth equal to the depth of the metal area with a modified structure, and the milling speed is optimal for the temperature Q ". 3 il. with $ (L with so; about o 00

Description

The invention relates to metal working, in particular, to the field of determining the optimal cutting speeds when machining steels with a carbide tool with a heated cutting layer, and can be used to designate cutting and heating modes when machining alloyed steels, heat-resistant alloys and other difficult-to-work metals and alloys in various industries mechanical engineering related to their machining.

The aim of the invention is to simplify by eliminating experiments involving the cutting of a heated metal, and accuracy.

Fig. 1 is a graph showing the change in ductility (cG) of steel type 35XH2CM versus heating temperature (b); FIG. 2 is a graph of the cutting temperature — the cutting speed; Fig. 3 is a check chart of tool life versus cutting speed during plasma heating treatment.

Consider the sequence of determining the optimal cutting speed during plasma-mechanical processing of sheet parts made of steel type 35XH2CM.

Heating of the stock removed by the mill is carried out in the process of plasma cutting.

According to the results of short-term tests, a graph of changes in plasticity (c) -steel versus heating temperature (Fig. 1) is constructed, from which the temperature of plasticity failure is determined.

Heating temperature is accepted. The onset temperature of the martensitic transformation (MHz) for this steel is 280 °.

Proceeding from the conditions of ensuring the highest possible productivity, the technical capabilities of the machine and the thickness of the sheets being processed (15-25 mm), the mm / min feed and plasma cutting modes A and B are assigned.

For selected treatment modes, the temperature at various points on the surface is measured using a pyrometer (or some other method). This makes it possible to position the Mill from the plasma torch at such a distance as to provide the heating temperature of the cutting layer.

at the time of removal, equal to the temperature at which the martensitic transformation begins.

In order to provide high-quality processing for these processing modes, the dimensions of the zone with a modified structure (thermal zone or HAZ) are determined. HAZ is determined experimentally (plasma cutting of samples is carried out in the same modes, then microsection is examined). To eliminate these experiments, a computer calculation program was developed.

To exclude parts with a modified structure, this value is taken as the milling depth.

To determine the cutting temperature, use the following relationship:

, (:.) P-K

0 5

zo

five

about

five

0

where 0p is the temperature of metal cutting without heating;

0j, f, is the temperature of plasticity failure;

N is the heating temperature (the onset temperature of the martensitic transformation); K is an experimental coefficient that takes into account the effect of heating on the properties of the workpiece.

br, g en + y0, (1)

where 5p, g temperature during processing

heated metal; Higher temperature; heating temperature; / 30 — temperature increment from the process of cutting a heated metal.

The value of & in can be represented in the form of K 0p, which characterizes the change in hardness and strength of the material being processed during the heating process. The value of K can be determined by the ratio of hardness in the initial and heated state, and to approximate the experimental conditions to the real conditions of the cutting process, it is necessary to take the dynamic hardness

to WY (2)

I A.WCX

where ND is the dynamic hardness of the workpiece (respectively, in the initial and heated states).

Substituted in formula (1) instead of е „-М„, Л0-бр., And 9р, - bar. we get

Bishop, Mn + to-er.,.

(bp n -My)

 eight

Rx

For this case

0р.,

K -iPSOO U 6600

940-280

0.65.

0.65

1010.

According to the graph, the cutting temperature – cutting speed determines the optimal cutting speed Vg 215 m / min.

Claims (1)

Invention Formula The method of determining the optimal cutting speeds of steels with a carbide tool, including determining the ductile dip temperature and plotting cutting temperatures — is the cutting speed that, in order to simplify and improve the accuracy in determining the optimal cutting speed By heating, the allowance is heated to a temperature above the austenitic transformation temperature, and the cut layer is removed in a cooled one. R. e n, l temperature of the martensitic transformation of states, the dimensions of the thermal zone are preliminarily determined and taken as the cutting depth, and the optimum cutting speed is determined by the dependence of the cutting temperature — the cutting speed in accordance with the cold cutting temperature, equal Ep.p. - -Mn time., -, where 9p is the cutting temperature during processing without heating; ductility dip temperature; the onset temperature of the martensitic transformation (the temperature at which the layer being cut is heated at the time it is removed); experimental coefficient taking into account the effect of roar on the properties of the workpiece; H nvgr (ms) is the dynamic hardness of the surface of the workpiece at the heated (initial) state. M K-VH iagr..ish 100 200 300 40Q 500 600 700 VOO 900 JOB C Phi2.1 Zoo 250 300 V, M / MU