GB2281308A - TiC containing tool material - Google Patents

Abstract

A tool material comprising between 70% and 90% by weight of titanium carbide dispersed in a matrix containing between 12% and 20% by weight of nickel and between 2% to 6% by weight of chromium, the chosen percentages totally 100%. Tool shapes are preferably made from blended powders of the constituents sintered by hot isotactic pressing to a fully dense form for use as press tools much as punch sleeves and inserts for ironing rings as shown in Figure 2. <IMAGE>

Description

TOOL MATERIAL AND TOOLS MADE THEREFROM This invention relates to tool materials comprising a hard material dispersed in a metal matrix or binder, and further relates to tools made from the material; more particularly this invention relates to punch sleeves blank holders and other tool parts of tools used in a press to make can bodies.

Cans drawn and wall ironed from sheet metal, are made in long stroke presses, examples of which are described in US Patents 3270544 (Maeder), US 3735629 (Paramonoff) and US 4173138 (Main) to which the reader is directed for a detailed description. In all these presses a long ram is about 40" long (l.Om) and supported by a pair of bearings spaced apart so that about half the length of the ram is supported in cantilever fashion as it passes through a sequence of wall ironing rings. The ram has a punch sleeve of cemented carbide material fixed to the end which passes through the wall ironing rings.A copious flow of an emulsion of lubricant in water is applied to a can on the punch, the ram and the ironing rings during wall ironing so the punch and wall ironing rings are subjected to axial force, a significant bending moment and impactive load in a wet environment.

The tool material commonly used for the punch sleeve and inserts in the ironing rings is usually tungsten carbide in a nickel or cobalt, tool steel or matrix.

Tungsten carbide in a cobalt matrix suffers from leaching out of the cobalt matrix to leave unsupported tungsten carbide. The tungsten carbide-in-nickel tool material has density of above 13 g/cc so the punch sleeve is a heavy mass which gives rise to bending of the ram and consequent impact with the entry to each ironing ring. Tool steel punch sleeves display relatively low resistance to wear compared to carbides, and are also prone to corrosion.

As cemented tungsten carbide tool materials are of high density and tool steel materials give poor in wear and corrosion performance, there is a need for a lighter carbide in a matrix resistance to wet environments.

Whilst materials based on titanium carbide in a steel matrix have provided a lighter tool in material used for certain can tooling applications, use of these materials in a wet environment would give rise to rusting of the matrix steel and these materials lack toughness.

Accordingly this invention provides a tool material comprising between 70% and 90% titanium carbide by volume randomly dispersed in a matrix comprising between 12% to 20% nickel by weight, and 2% to 6% of chromium by weight, said percentages chosen totalling substantially 100%.

Preferably the tool material is formed by sintering powder, the particle size distribution of the titanium carbide being between 1 and 4Am. The particle size of the nickel and chromium being less than 3 sum. The density of the sintered tool material is less than 8g/cc.

The tool material may be used to make various tools such as punch sleeves, blank holders, die inserts or stripper fingers for a press tool such as is used to make drawn hollow articles.

Various embodiments will now be described by way of example and with reference to the accompanying drawings in which: Figure 1 is a schematic sectioned side view of a known press used to draw and wall iron can bodies; and Figure 2 is an enlarged sectioned side view of a punch sleeve, die, stripper and doming station incorporating the tool material.

Figure 1 shows diagramatically a typical form of long stroke press used to redraw a cup to a reduced overall diameter which is then passed through at least one ironing ring to reduce the thickness and increase the length of the redrawn side wall of the cup.

In Figure 1 the press 1 comprises a frame 2 which supports a tool pack 3 comprising a redrawing die 4, three ironing rings 5 and a stripper 6. A bottom forming pad 7 is axially aligned with the tool pack 3.

The press has a first action assembly comprising a long ram 8 supporting a punch 9, a connecting link 10, a lever arm 11 and a connecting rod 12 operably connected to a crank shaft 13 so that rotation of the crank shaft moves the punch 9 in and out of the tool pack 3. The lever arm 11 swings on a pivot 14 mounted in a block 15 on the frame.

The press has a second action assembly comprising a blank holder 16 mounted on a crosshead 17 connected to a pair of long push rods 18, 19 shown cut away in Figure 1, which extend to a spreader plate 20 which is coupled to a pair of second levers one of which is visible and denoted 21 which engages with a follower 22 engaged with a cam 23 on the crank shaft. An air cylinder 24 urges the follower on the second lever 21 to follow the rotating cam surface as movement of the lever and rods 18, 19 and crosshead 17 moves the blank holder towards the tool pack.

In use, the cam 23 controls the blank holder motion to enter a cup fed from feeder chute 25 and press the cup against the surface of the redraw die 4. The first action assembly then moves the ram 8 with punch 9 into the cup to drive the cup through the tool pack until it strikes the bottom forming pad 7. On the return stroke of the punch/ram a drawn and wall ironed can 35 is stripped from the punch by the stripper 6.

The ram 8 and wall ironing rings 5 in the tool pack 3 are continuously flooded by an emulsion of lubricant in water which acts as a coolant and lubricant during wall ironing. The emulsion is delivered and distributed in the tool pack through a pipe 30 leading from a pump 31 which lifts the emulsion from a tank 32 to which spent lubricant is returned.

A problem arising in this sort of press is that the punch and ram assembly is long and slender, typically over a metre long by about 65mm diameter. The ram is supported by a pair of hydrostatic bearings 27, 28 and a slide way 29 (shown in dashed lines) which supports a coupling 30 which joins the ram 8 to the connecting link 10. However, there persists a problem of vibration of the punch arising from impact with the bottom doming pad and a problem of punch alignment with the tool pack because the weight of the punch causes the ram to droop.

The purpose of the blank holder 16 is to firstly enter the cup and centre it with respect to the redrawing die 4, and then apply an even pressure to a peripheral portion of the bottom of the cup to prevent wrinkling of the side wall of the cup as it is drawn to reduced diameter and greater height. Problems arise because: a). the long slender ram droops slightly so striking each ironing ring.

b). the punch, ram and ironing rings work in a wet environment capable of corroding or erroding the matrix of tool materials used hitherto; c). vibration and inertia forces arising in the ram are increased by the mass of punch material.

These problems may be reduced by use of tool material comprising a lighter hard material randomly dispersed in a matrix resistant to acqueous corrosion and erosion.

One such material comprises between 70% and 90% by weight of titanium carbide randomly dispersed in a matrix comprising between 12% and 20% by weight of nickel and between 2% and 6% by weight of chromium said percentages chosen totalling substantially 100%.

This tool material is preferably made by mixing powders of the constituents which are then compacted and sintered, preferably by hot isotactic pressing, to a fully dense form in a desired shape. The particle size distribution of the titanium carbide is between 1 and 4yam. The particle size of the nickel and chromium powders is preferably less than 3.

The density of the sintered mixture of powders is less than 7 g/cc and comprises discrete particles of titanium carbide dispersed in a nickel/chromium matrix.

A titanium carbide content greater than 90% will impair toughness. A titanium carbide content less than 70% will impair resistance to wear.

A nickel to chromium ratio below 2 to 1 will promote embrittlement, whilst a nickel to chromium ratio above 10 to 1 will degrade resistance to corrosion and wear.

This tool material is suitable for use as the punch sleeve 9, die insert 5a in wall ironing rings, doming pad 7 and stripper fingers 6a as shown in Figure 2.

As shown in Figure 2, the punch sleeve 9 is in the form of a tube of tool material which is a sliding fit on the end of the ram 8 to which it is retained by a core member.

The doming pad 7 is preferably housed in a recess in holding material (not shown); and the stripper fingers 6a may have a pad of tool material bonded to their working surface or alternatively be made entirely of the tool material.

Claims (7)

1. A tool material comprising between 70% and 90% by weight titanium carbide dispersed in a matrix containing between 12% and 20% by weight nickel and between 2% and 6% by weight of chromium said percentages chosen totally substantially 1008.

2. A tool material according to claim 1 made by sintering powders of said titanium carbide, nickel and chromium to a random dispersion of titanium carbide in a nickel chromium matrix with compaction to a density less than 7g/cc.

3. A tool material according to claim 2 wherein the titanium carbide powder has a particle size distribution between 1 lvum and 4jim.

4. A tool material according to claim 3 wherein the nickel and chromium powders have a particle size less than 3 pm.

5. A tool material according to any proceding claim when the form of a punch sleeve, blank holder, the insert or stripper finger.

6. A tool material substantially as herein before described with reference to the accompanying examples.

7. A tool material in the form of a tool substantially as here in before described with reference to Figure 2 of the accompanying drawings.