DE1458426C3 - Austenitic cast iron with spheroidal graphite - Google Patents

Description

Austenitic types of cast iron are high-alloy materials that, because of their multiple physical and technological properties a great deal. have meaning. In contrast to unalloyed cast iron these materials are free from structural changes; they are fully austenitic, d. i.e., their grille is Cubic area-centered. Most of the carbon is graphite. Differed the material groups austenitic cast iron with lamellar graphite and austenitic cast iron with Spheroidal graphite.

A cast iron with flake graphite is known as follows Composition in percent by weight:

2 , 5 until 5.3% Carbon, 1 , 25 until 2.25% Silicon, 0 , 7 until 1.5% Manganese, 12th until 16% Nickel, 1 until 6% Chrome, 5 until 8th% Copper, rest Iron.

Max. 3% Carbon, 1.75 until 3% Silicon, 0.7 until 1.0% Manganese, 18th until 22% Nickel, 1.75 until 2.5% Chrome, rest Iron.

Max. 2.4% Carbon, 1.5 until 2.75% Silicon, Max. 0.5% Manganese, 34 until 36% Nickel, 2p until 3% Chrome, Remainder iron.

The known austenitic cast iron alloys with spheroidal graphite have a higher tensile strength, which amounts to 37 to 50 kp / mm ² for the various types. However, they have no copper content. However, their nickel content is high and amounts to 18 to 36 percent by weight for the various types.

An austenitic cast iron with spheroidal graphite with only 12 to 14 percent by weight is also known Nickel, but with a comparatively high manganese content of 6 to 7 percent by weight is. This alloy also has no copper.

So far, the view would be that for Production of austenitic cast iron is over 3 percent by weight Excessive amount of copper in the alloy leads to the crystallization of the graphite in The graphite prevents spherical shape after solidification the melt is in lamellar form.

Furthermore, the austenitic cast iron Formation of spheroidal graphite with a proportion of max. 4% copper is only considered possible if high-purity special pig iron in the form of Swedish charcoal iron in connection with selected Steel scrap would be used. Charcoal irons are very expensive to use and to use of selected steel scrap associated with such difficulties that the large-scale Production of austenitic cast iron with spheroidal graphite in the presence of copper in practice would not be done.

The present invention is based on the object of an austenitic cast iron with spheroidal graphite to create with a copper content of more than 4% and in an economical way when using usual Manufacture of pig iron and steel scrap.

The cast iron alloy of the invention of austenitic Structure with spheroidal graphite has the following composition in percent by weight:

With a high proportion of copper, this austenitic cast iron has no carbon in the form of spheroidal graphite, but lamellar graphite and, within the specified analysis ranges, only a tensile strength of 14 to 18 kp / mm ² with an elongation of only 1.6 to 2%.

An austenitic cast iron alloy with spheroidal graphite of the following composition is also known:

1.5 until 3 Vo Carbon, 1 until 5 <Vo Silicon, 0.3 until 4% Manganese, 12th until 18% Nickel, 0.5 until 5% Chrome, 5.0 until 9% Copper, 0.03 until 0.2% Magnesium, 0.02 until. 0.2% Aluminum, rest Iron and melt-related defects cleaning like Phosphorus and sulfur.

An austenitic cast iron alloy with spheroidal graphite of the following composition is particularly advantageous whose structure is shown in the figure:

An austenitic cast iron alloy with spheroidal graphite with the following composition is also known:

2.5% Carbon, 2.5% Silicon, 1% Manganese, 14.5% Nickel, 6.5% Copper, 2.5% Chrome, 0.07% Magnesium, 0.025% Phosphorus, 0.008% Sulfur, 0.05% Aluminum, rest Iron and trace elements

The alloys according to the invention have a tensile strength of 38 to 60 kp / mm ² , a yield point of 30 to 50 kp / mm ² and an elongation of 5 to 20 ⁰ I ₀ (Lo = 5 D), measured on the short proportional rod. They are also corrosion-resistant and resistant to oxidation "against attack by dilute acids, sea water and salt solutions. They have good sliding properties with a high load-bearing capacity and are non-frangible with low chromium contents.
The austenitic cast iron alloys with spheroidal graphite proposed according to the invention have a strength with comparatively only small proportions of nickel of 12 to 18%, which is at least equivalent to the values of the previously known austenitic cast iron alloys with spheroidal graphite with contents of 18 to 36% nickel. With the alloys proposed according to the invention, a tensile strength of 60 kp / mm * and a yield point of 50 kp / mm * can be achieved.
The austenitic cast iron alloys proposed according to the invention also show improved corrosion resistance and have good resistance to oxidation, especially in dilute acids, seawater and salt solutions. In addition, the

Very good sliding properties with high load-bearing capacity. she are still not magnetizable with low chromium contents.

The austenitic cast iron alloys with spheroidal graphite proposed according to the invention can be found on p advantageous use for sliding and sealing rings in pumps and fittings, combustion chambers and charging housings for internal combustion engines ,, furnace components for heat treatment furnaces, non-magnetizable Cast parts and press covers for generators, push plates for electromagnets, housings for switchgear and seawater-resistant components.

The austenitic cast iron alloys with spheroidal graphite proposed according to the invention are produced in such a way that pure alloying elements, in particular copper in the form of electrolytic copper, are added and small amounts of aluminum, also in the form of aluminum-containing ferro-silicon or calcium-silicon alloys, are added to the inoculating alloy are added, wherein the aluminum addition of 0.02 to 0.2 ° / _0, based on the total weight of the melt, is.

It has been shown that small amounts of aluminum as an additive to the melt, the disadvantageous influence of copper on the formation of spheroidal graphite significantly reduce or switch off.

Have the inventively proposed austenitic spheroidal graphite cast iron alloys with increasing chromium and silicon content to each of 5 ° / ₀ a particularly high corrosion, erosion and oxidation, together with high yield strength. It has been found that optimal values are / _{0 is} reached in the strength properties when chromium contents of from 2 to 3 °. Increasing chromium contents continue to lead to increasing carbide deposits and a resulting increase in wear resistance.

The austenitis proposed according to the invention Cast iron alloys with spheroidal graphite compared to the known alloys with equivalent Properties have the advantage of significantly lower operating costs, because a greater "hedge" of the expensive Nickel is replaced by the inexpensive copper;

Claims (1)

Patent claims: 1. Austenitic cast iron with spheroidal graphite, characterized by the following 2ü
setting: 45 1.5
1.0
0.3
12th
0.5
5.0 to 3%
until 5%
to 4%
up to 18 ° / o
until 5%
till 9% Carbon, Silicon, Manganese, Nickel, Chrome, Copper, 0.03 to 0.2% magnesium,
0.02 to 0.2% aluminum,
The remainder is iron and impurities from the melt such as phosphorus and sulfur. 2. Austenitic cast iron with spheroidal graphite according to claim 1, characterized by the following Composition: 2.5 per cent Carbon, 2.5% Silicon, 1.0% Manganese, 14.5% Nickel, 6.5% Copper, 2.5% Chrome, 0.07% Magnesium, 0.025% Phosphorus, 0.008% Sulfur, 0.05% Aluminum, Remaining iron and trace elements: 3. A method for producing austenitic cast iron with spheroidal graphite according to claims 1 and 2, characterized in that pure alloy elements, in particular copper in the form of electrolytic copper are added and small amounts of aluminum are added to the inoculating alloy, also added in the form of aluminum-containing ferro-silicon or calcium-silicon alloys be, the aluminum addition 0.02 to 0.2%, based on the total weight of the Melt. 4. Use of an austenitic cast iron alloy with spheroidal graphite according to claim 1 or 2 as a material for objects that have a tensile strength of 38 to 60 kp / mm ² , a yield point of 30 to 50 kp / mm ² and an elongation of 5 to 20%, measured on the short Pfoportionalstäb, also have corrosion resistance against the attack of dilute acids, sea water and salt solutions and must have good sliding properties with high load-bearing capacity and non-magnetism. 1 sheet of drawing