DE2734408C2 - Process for the manufacture of high speed tools - Google Patents

Description

The invention relates to a method for the production of high-speed tools with niobium or niobium / vanadium precipitated carbides in addition to eutectic carbides rich in tungsten and molybdenum.

From GB-PS 8 73 529, which is mainly concerned with the alloying composition of high-speed steels, steel compositions are known which contain 0.6 to 2% carbon, 1% silicon, 1% manganese, 3 to 10% chromium , 0 to 12% molybdenum, 0.5 to 23% tungsten, 0 to 8% vanadium, 0 to 23% cobalt, up to 0.5% nitrogen, 0 to 3% aluminum, 0 to 3% boron. 0 to 6% titanium . 0 to 6% zirconium, 0 to 10% niobium, 0 to 10% tantalum and the remainder iron. The tools are produced by casting, which is followed by a heat treatment, which consists of annealing for one to eight hours at 1050 to 1200 ^° C. and hardening by quenching from a temperature between 1200 and 1350 ^° C. with subsequent tempering to temperatures / wipe 500 and 600 ⁰ C exists. Forged tools are made from a steel that contains 1.25 to 1.45% carbon, 12.5% tungsten, 4% chromium, 4% vanadium, 5% cobalt and the remainder iron. The cast tools have a longer service life than the forged ones Tools.

The object of the invention is to be seen in a method for producing high-speed tools to create whose service life exceeds the tools that are made of forgeable steel according to the GB-PS 8 73 529 are made.

ίο This task is solved with the im Claim 1 indicated measures. Further advantageous refinements of the invention are set out in the claims 2 and 4.

The invention is explained, for example, with reference to the drawings.

Show in the drawings

1 to 3 show typical microstructures of carbides in the as-cast state;

4 to 7 show the morphological control of the particle shape of the special carbides;

F i g. 8 the influence of the increase in the niobium content and the simultaneous decrease in the vanadium content; F i g. 8 to 13 are graphs of hardness;

Figs. 14 and 15 are graphs of grain size and that, respectively Service life.

Typical microstructures of carbideu of the erfindungsg <; according to the manufactured alloy in the as-cast state with a basic composition of 4.0% chromium, 8.0% tungsten, 4.5% molybdenum, 10% cobalt and different contents of vanadium and niobium are in F i g. 1 to 4, all obtained at 200X and without etching, and although F i g. 1 with 0.2% vanadium and 2.5% niobium, FIG. 2 and 3 with 2.7% niobium and F i g. 4 with 0.5% vanadium and 2.2% niobium. In Figs. 2 and 3 are the different Morphologies can be recognized which the individual carbides can adopt (square or thread-like).

In general, the morphology of the precipitation carbides or special carbides by the vanadium content, the niobium content, the ratio of niobium to Vanadium, the action of aluminum or other deoxidizers and the manufacturing process influenced.

The shape of the special carbide is controlled by the use of deoxidizing agents, such as Aluminum, titanium, rare earth metals, calcium, silicon, zircon and combinations thereof in one Quantity up to 0.4% of the total batch. The effect of aluminum is shown in Fig. 5 (200x magnification,

without etching). The deoxidation can also be carried out under vacuum, ie at pressures of less than 6650 N / m ² , the effect in FIG. 6th

(200X magnification, without etching) is shown.

Sometimes such techniques are not required if a small grain size iron-niobium alloy, about less than 0.56 mm, is used and when casting is carried out immediately after this state.

The morphology of the special carbides changes in the end product depending on the structure in the As cast, the vanadium and niobium content. the manufacturing process in the steelworks and the one used Thickness decrease during rolling. F i g. 7 (in the table alloy 2) shows an enlargement of 100 times electrolytic etching and the distribution and size of the special carbides.

Such alloys have a formability for forging and rolling that is comparable to that in the trade available alloys with a similar composition

/ iing 'is equivalent. and can be in a conventional line Plant can be forged and rolled.

The heat treatments of these alloys are carried out in salt baths, with austenitizing at 1100 to 12fcO 'C is run with a cool down to for 13 minutes in a further bath held at 400 to 100'C and with a further cooling Lull. Tempering takes place, depending on the desired hardness, at 400 to 650 ° C and at least twice Avoidance of an excessive amount of residual plastic.

Tabel

To avoid decarburization, ovens that work with a school atmosphere or even with a vacuum can be used. Austenitizing success: emperaturbercich in the above Ί. The hardnesses achieved after hardening and tempering in salt baths for alloys 1 to 5 are shown in FIGS. 8 to 13. These tempering curves were obtained by changing the Auslenitisicrungstemprair from 1180 to 1240 "C.

alloy

Si

Mn

Al

Cr

Mon

Nb

Co

0.87

0.47

0.31

0.029

0.029

0.002

3.71

7.97

4.31

2.68

0.008 9.76

1.14
0.34
0.26
0.031
0.030
0.010
4.12
7.75
4.52
2.65
0.20
0.009
10.02

1.18
0.30
0.23
0.029
0.025
0.009
3.93
8.18
4.38
2.18
0.51
0.010
10.00

1.26

0.38

0.24

0, U27

0.023

0.011

3.90

8.28

4.58

1.63

0.91

0.009

9.70

The introduction of niobium reduces the austenite grain size determined by the Snyder-Graff process. Such a reduction depends on the morphology and distribution of the special carbide and of the at Rolls applied decrease in thickness. This effect is in Figure 14 for certain compositions shown. Alloy 2 experienced the greatest decrease in thickness.

Tools made from such alloys were tested for machinability in comparison to an alloy without niobium and with vanadium (1.3% C, 4.20% Mn). The tool made from this alloy was designated with A. The woe ¹ ! Tools were designated as follows:

B alloy I
D alloy 3
F alloy 4
F alloy 5

Clearance angle

Exit angle

Tilt angle

Angle of attack

Radius of curvature

+ 7 + IO + 4 + W) 1 mm

The tools used
Geometry:

hold do the following Fs, a feed rate of 0.202 mm per revolution was used with a cuticle of p = 2 mm.

The material machined in this way was a steel SAF-4 340 which was hardened and on A hardness of 300 HB winch started. The service life

4 "> of the tool as a function of the wedge depending on the cutting speed is in Fig. Ib at a wear zone from /; = 0.6 mm shown.

The steels made from the steels according to the invention manufactured tools have a much longer time

Ι »Tool life than tools made from steel or niobium. For example, this tool b made from alloy 6 at a cutting speed of 35 m / min has a service life that is 100% longer than tool A. that made from an alloy without niobium

V) is established.

In addition 7 sheets of drawings

Claims (4)

Patent claims: 1. Process for the production of high-speed tools with niobium or niobium / vanadium precipitated carbides in addition to eutectic carbides rich in tungsten and molybdenum, characterized in that that a steel consisting of 0.7 to 1.50% carbon, 0.1 to 1.0% silicon, 0.15 to 0.50% manganese, a maximum of 0.03% phosphorus, a maximum of 0.20% sulfur, 3.50 to 6.0% chromium, greater than 0 to 10.0% molybdenum, greater than 0 to 10% tungsten, 0 to 4.0% vanadium, 0.2 to 12.0% cobalt, at most 0.08 % Nitrogen and a maximum of 0.25% aluminum, 0.1 to 7.0% niobium, the remainder iron with usual impurities, with aluminum, titanium, rare earth metals, calcium, silicon, zirconium or combinations thereof in an amount up to 0.4 % of the entire batch is deoxidized, the steel is forged or rolled after casting and then subjected to a heat treatment in which salt baths and austenitizing temperatures of 1100 to 1260 ⁰ C are used, cooling takes place in a ^{bath maintained at 400 to 650 0} C and further cooling in air, and tempering at 400 to 650 ^° C. is carried out at least twice. 2. The method according to claim 1, characterized in that the charge is deoxidized ^{under vacuum at pressures of less than 6650 N / m 2.} 3. The method according to claim 1 or 2, characterized in that an iron-N for deoxidation iob alloy with a grain size of less than 0.59 mm at the end of melting immediately added before pouring from the oven. 4. The method according to any one of claims 1 to 3, characterized in that instead of molten Salt baths austenitizing in furnaces with a controlled atmosphere or under vacuum is carried out.