Use of Sormite-Type Alloys for Dies
Abstract Generated abstract
This paper examines the use of cast sormite-type alloys as materials for dies, where deposited hard alloys had already shown improved wear resistance but were difficult or impossible to apply in some tool geometries. Five chromium, carbon, nickel, silicon, and manganese iron alloys were prepared by high-frequency melting, cast in sand molds, and tested to determine suitable oil-quenching temperatures across 800 to 1200°C. Hardness measurements indicated that raising the quenching temperature above about 950 to 1000°C reduced hardness, likely because of increased alloying and retention of austenite. Production trials with cast bending and drawing dies showed service lives approximately two and three times greater, respectively, than comparable Kh12 steel dies, suggesting that cast sormite-type alloys may be useful for selected die applications.
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USE OF SORMITE-TYPE ALLOYS FOR DIES
V. A. Samylov
(Presented by Professor, Doctor A. N. Dobrovidov)
Sormite-type alloys have a fairly wide application in industry and are used for manufacturing wear-resistant machine parts and tools—parts of stone crushers, teeth of excavator buckets, knives for cutting metal, etc.
In the overwhelming majority of cases, alloys of this type are used as a material deposited onto parts by various methods: surfacing with an oxyacetylene flame, welding with an electric arc, and surfacing by means of high-frequency currents.
For dies and other tools, deposited alloys have been used only recently. Their field of application is limited to dies and punches of bending and drawing dies, simple blanking dies, metal knives, and measuring instruments. Since a built-up tool shows a service life several times greater than that of a non-built-up one, the advisability of using sormite-type alloys is obvious.
However, not all tools are convenient to build up or weld, and in some cases this is impossible (for example, the surface of the inner diameter of a small drawing die). Furthermore, when welding, it is difficult to obtain a high-quality surface layer of alloy that is precise in chemical composition; therefore attempts to obtain cast dies from a sormite-type alloy are quite natural.
The service life of sormite dies for drawing dies is 16–20 times greater than the service life of dies made of carbon steel.
The use of cast sormite-type alloy for bending and blanking dies has not been covered in the literature; heat-treatment regimes require more detailed investigation. As for data from service-life tests of sormite dies in comparison with Kh12-type steels, the most widely used for dies, none are available at all. The purpose of our work was to find heat-treatment regimes and to obtain the results of service-life tests of dies with cast dies made of a sormite-type alloy under production conditions.
According to the literature, the chemical composition of sormite-type alloys varies within the following limits:
\[ \begin{aligned} \mathrm{C} &= 1.5\text{--}3.5\%, \qquad \mathrm{Cr} = 13.5\text{--}31.0\%, \qquad \mathrm{Mn} = 0.5\text{--}1.5\%,\\ \mathrm{Ni} &= 1.5\text{--}7.0\%, \qquad \mathrm{Fe} = \text{balance}, \qquad \mathrm{Si} = 0.6\text{--}4.0\%. \end{aligned} \]
The percentage composition of the alloys we studied is given in the table.
Table
| Alloy No. | C | Cr | Mn | Si | Ni | Fe |
|---|---|---|---|---|---|---|
| 1 | 1.72 | 17.75 | 1.41 | 2.30 | 2.98 | remainder |
| 2 | 1.80 | 18.40 | 1.20 | 2.58 | 3.09 | remainder |
| 3 | 2.30 | 16.00 | 1.40 | 1.90 | 1.70 | remainder |
| 4 | 3.00 | 17.60 | 1.09 | 3.60 | 2.18 | remainder |
| 5 | 3.40 | 17.00 | 1.00 | 2.87 | 2.49 | remainder |
The indicated alloys were obtained by melting Kh12 steel scrap with additions of ferrochrome, nickel, ferrosilicon, and ferromanganese in a three-kilogram graphite crucible in a melting high-frequency installation.
The crushed materials were charged with ground graphite, and the melt was deoxidized with aluminum, at the rate of 1 g of aluminum per 1 kg of alloy. Pouring was carried out into a dry sand mold; the pouring temperature was determined by means of an optical pyrometer.
To determine the heat-treatment conditions, specimens of each alloy indicated in the table were taken and quenched in oil, with heating carried out within the range from 800 to 1200°C in 50°C increments. Each specimen was quenched only once.
The change in the hardness of the alloy as a function of the quenching temperature is shown in Fig. 1, from which the quenching temperature for each of the indicated alloys can be selected. Analysis of Fig. 1 shows that, when the quenching temperature is raised above 950–1000°C, the hardness of the alloys decreases, which is explained by an increase in the degree of alloying of the austenite formed and, consequently, by an increase in its amount.
Fig. 1. Effect of quenching temperature on the hardness of alloys Nos. 1, 2, 3, 4, and 5.
Production Tests of Cast Dies
Cast dies were made for two dies: a bending die from alloy No. 4 and a drawing die from alloy No. 5.
The bending die operated satisfactorily under production conditions and failed as a result of wear of the working part of the die; at the same time, its service life was twice that of an identical die made of Kh12 steel. Since no cracks were found on the die, one may hope that an alloy with a high carbon content can be used for a bending die. The drawing die with a matrix made of alloy No. 5, when tested under production conditions, showed a service life three times greater than that of an identical die made of Kh12 steel.
References
- I. V. Trush, V. A. Sechko—Cast dies made of sormite alloy No. 1, Stanki i instrument No. 11, 1956.