CS254887B1 - Cast iron with high abrasion resistance - Google Patents

Abstract

Cast iron with high abrasion resistance intended for the production of parts exposed to intensive wear by abrasive particles, e.g. for slag crusher hammers, has a composition of 2.8 to 3.1 wt. % carbon, 24.0 to 26.0 wt. % chromium, 0.3 to 1.0 wt. % manganese, 0.3 to 1.0 wt. % silicon, 0.1 to 0.2 wt. % titanium, 0.1 to 0.2 wt. % aluminium and 0.05 to 0.1 wt. % boron. For heavier castings, cast iron also contains from 0.4 to 0.6 wt. % nickel and 1.0 to 1.5 wt. % molybdenum. As a technological additive, cast iron contains cerium in an amount of from 0.05 to 0.1 wt. %

Description

The invention relates to cast iron with high abrasion resistance, intended for the production of parts exposed to intensive wear by abrasive particles.

Currently, a number of variants of cast irons of the Fe-Cr-C system with an increased chromium content and possibly with the addition of other elements are used for this purpose. The reason for the higher chromium content is the fact that from about 10% by weight of chromium in these cast irons, hexagonal carbide M?C ₃ crystallizes at the end of their primary crystallization as one of the quasieutectic phases, which has a higher hardness than cementite and cast irons with this carbide also show a lower tendency to brittle fracture.

They are used in a hardened or low-tempered state. This, among other things, results in the requirement for their good hardenability in the production of parts of greater mass? for this purpose, the basic composition is usually modified by the addition of molybdenum, nickel or copper, which improve their hardenability. Abrasion resistance is most significantly influenced by the carbon content in cast iron, but this is limited by the concentration corresponding, for a given overall cast iron composition, to the position of the interface between the austenitic field and the area of primary crystallization of carbide M^C ₃ , when exceeded when the carbon content in cast iron increases, the tendency of cast iron to brittle fracture significantly increases and the resistance of cast iron to abrasion also decreases.”

The above-mentioned disadvantage is eliminated by the cast iron with high abrasion resistance according to the invention, containing from 2.8 to 3.1 wt. % carbon, from 24.0 to 26.0 wt. % iron, from 0.3 to 1.0 wt. % manganese and from 0.3 to 1.0 wt. % silicon. The essence of the invention is that the cast iron further contains aluminum in an amount of from 0.1 to 0.2 wt. %, titanium from 0.1 to 0.2 wt. %, boron from 0.05 to 0.1 wt. % and as a technological additive cerium from 0.05 to 0.1 wt. %. According to another feature, the cast iron with high hardenability intended for castings of larger weights further contains nickel in an amount of from 0.4 to 0.6 wt. % and molybdenum from 1.0 to 1.5 wt. %.

The advantage of the cast iron according to the invention is that it has approximately 30% higher abrasion resistance than the corresponding type of cast iron used for the above purposes, with comparable or higher resistance to brittle fracture.

The cast iron according to the invention is the result of a theoretical study of the primary crystallization of cast irons of this type and the influence of the thermodynamic interaction between the atoms of the alloying elements on the mechanism of this crystallization and the displacement of the above-mentioned interface. The alloying elements, on the one hand, have a positive effect on the nucleation process of the cast iron by increasing the dispersion of both the matrix and the eutectic phases, thereby reducing its tendency to brittle fracture and increasing its resistance to abrasion. The alloying elements also form hard carbides that crystallize in the matrix and thereby increase its resistance to abrasion, while due to their high dispersion they do not increase the tendency of the cast iron to brittle fracture.

For these purposes, the cast iron in the variant for castings of smaller weights is alloyed with aluminum, titanium and boron, and in the second variant, characterized by high hardenability and intended for the production of heavier castings, additionally with nickel and molybdenum. In both of these cast irons, a technological additive of 0.05 to 0.1 wt. % cerium is preferably used, which favorably affects their nucleation mechanism, thereby improving their mechanical properties and resistance to abrasion.

Cast iron with high abrasion resistance is illustrated in more detail in the following examples. For comparison, the composition and properties of the Cr 25 cast iron produced to date, used for the production of deflector bars for Wageneder slag crushers, are given. Table 1 shows the composition of the comparative Cr 25 cast iron (designation A) and the cast iron according to the 1st point of the subject of the invention (designation B) and the 1st + 2nd points of the subject of the invention (designation C).

Table 1

Cast iron

CrMnSi

Ti Al B

Ni

Mo

A 2.91 24.97 0.76 0.84 B 2.90 25.02 0.68 0.77 0.19 0.14 0.11 C 2.95 24.95 0.70 0.72 0.20 0.09 0.09 0.62 1.30

Table 2 shows the properties of all three cast irons, namely in the as-cast state (designation 1), soft-annealed at 800 °C/4 hrs/furnace (designation 2), soft-annealed and quenched 950 °C/1 hrs/air (designation 3) and soft-annealed and quenched 950 °C/1 hrs/furnace 1 °C/min. (designation 4).

In addition to the abrasion test loss values, the hardness of the material is also an important material factor, as it significantly affects the economics of machining parts.

The property values after very slow cooling from the quenching temperature simulate the effect of larger casting thicknesses on these properties.

Table 2

Cast iron Heat processing Hardness HV 10 Max. deflection (mm) Abrasion test resistance (g) A 1 525 0.55 0.35 560 0.60 0.36 2 390 - - 425 - - A 3 734 0.45 0.35 792 0.51 0.37 4 525 0.73 0.48 570 0.82 0.50 1 579 0.47 0.27 620 0.52 0.29 2 345 - - B 373 - 3 613 0.52 0.24 681 0.54 0.26 4 317 0.63 0.40 357 0.85 0.42 1 572 0.17 627 - 0.18 2 464 - . - C 503 - - 3 627 0.36 0.16 707 0.49 0.18 4 357 0.55 0.36 402 0.68 0.40

The cast iron according to the invention can be used for the production of components such as bars or hammers of crushers for grinding slag or limestone, lining of hopper chutes on bell-ends of blast furnaces, containers for substrates, buckets of throwing wheels, parts of hauling and granulating pumps and the like.

Claims (2)

SUBJECT OF THE INVENTION 1. Cast iron with high abrasion resistance, containing from 2.8 to 3.1 wt. % of carbon, from 24.0 to 26.0 wt. % chromium, from 0.3 to 1.0 wt. % manganese and from 0.3 to 1.0 wt. % of silicon, characterized in that it contains aluminum in an amount of from 0.1 to 0.2% by weight, titanium from 0.1 to 0.2% by weight, boron from 0.05 to 0.1% by weight. and as a technological additive cerium from 0.05 to 0.1 wt. 2. The cast iron according to claim 1, further comprising nickel in an amount of from 0.4 to 0.6% by weight. and molybdenum from 1.0 to 1.5 wt.