SU1339160A1 - Wear-resistant cast iron - Google Patents

Abstract

The invention relates to a foundry, namely, to the search for compositions of high-carbon iron alloys. The aim of the invention is to reduce the tendency of pig iron to foil formation, to increase its fluidity, abrasive and hydroabrasive resistance when operating in alkaline media containing silica. The proposed cast iron has the following composition, wt.%: Carbon 3.0-3.5; silicon is 1.5-3.0; manganese 0.1-0.8; sulfur 0.06 - 0.08; antimony 0.05-0.8; molybdenum 0.1-0.5; chromium 0.03-0.6; boron 0.08-0.2; nitrogen 0.02-0.2; phosphorus 0.1-0.8; iron - the rest. Cast iron of such a composition can be used in the manufacture of parts of valves, pumping corrosive media containing particles of abrasive material. 2 tab. O) co; o

Description

The invention relates to a foundry, in particular, to compositions of high carbon iron alloys, and can be used in the production of castings operating under conditions of abrasive and hydroabrasive wear in alkaline media containing particles of abrasive material.

The purpose of the invention is to reduce the tendency of pig iron to foaming, to increase the fluidity, abrasive and hydroabrasive resistance of castings when working in alkaline media containing silica.

Cast iron of the proposed composition contains, wt%:

Carbon 3.0-3.5

Silicon1, 5-3,0

Manganese O, 10-0.8 Sulfur 0.06-0.08

Antimony 0.05-0.8

Molybdenum, 1-0,5

Chrome 0.03-0.6

Bor0.08-0.2

Phosphorus 0.1-0.8

Nitro0.02-0.20

IronErest

The limits of the content of the components are established, on the basis of obtaining the most favorable combination of the structure of the casting, mechanical, and service characteristics of the alloy.

The lower limit on the carbon and silicon content (3.0 and 1.5 wt.%) Is due to the necessity of patching the pearlite metal matrix and satisfactory technological properties, first of all, the fluidity of the melt. The upper limit on the carbon and silicon content is 3.5 and 3.0 mass%, respectively, of each element is limited to obtaining in the structure of the ferrite component no more than 5%.

The limits of the content of manganese (0.10 0.8% by weight), boron (0.08-0.2% by weight) and molybdenum (0.1-0.5% by weight) are chosen experimentally, based on the maximum hardening metal base of cast iron due to grinding of graphite inclusions, stabilization of pearlite, increasing its dispersity and microhardness. The content of manganese, boron and molybdenum below the lower limit leads to a sharp decrease in the strength characteristics, and above the upper limit it is not economically feasible.

Chromium in the composition of cast iron leads to the formation of ledeburite, which significantly increases the hardness of the material.

Chromium lower limit

(0.03 wt.%) Is limited by the effect of increasing hardness, the upper (1.0 wt.%) Is due to a decrease in fluidity and an increase in the tendency of cast iron to

foaming.

Antimony is the perlithizer of the iron cast iron base. Present in the alloy and contribute to the supercooling of the melt, changes the shape and

graphite dimensions. The total number of inclusions of graphite with the addition of antimony increases, which favorably affects the increase in wear resistance of the iron. Upper limit of antimony content

(0.2 wt.%) Is limited to a small increase in the perlitisation effect, the lower (0.05 wt.%) Is due to the achievement of the required accuracy.

Phosphorus substantially increases the fluidity of high-carbon alloys. In addition, in the presence of antimony, phosphorus in cast iron forms a complex phosphide-antimony eutectic with greater hardness (H 730 kg / mm)

compared to conventional phosphide

(H 580 kg / mmO. The addition of phosphorus crushes the eutectic grain, and the phosphide antioxidant eutectic, located at the grain boundaries in the form of a broken mesh, due to its high hardness increases the abrasive and hydroabrasive resistance of cast iron. wt.%) limited to

the maximum hardness of the alloy, the lower limit (0.1 wt.%) is set due to the reduction of the fluidity of cast iron.

When nitrogen is introduced into the pig iron, it substantially crushes the eutectic grain, which affects the increase in the mechanical properties of the iron. The increase in wear resistance due to additional micro-alloying of cast iron with nitrogen is explained by the formation of dispersed boron nitrides evenly distributed in the volume of the metallic base of the cast iron. When the nitrogen content is up to 0.02 wt.%, Its effect is insignificant, and with an increase in its concentration (more than 0.2 wt.%), The wear resistance decreases due to the coarsening of nitride inclusions, and the fluidity decreases. Optimal conformance

wearing nitrogen and boron in phosphorus and antimony iron 1: 1.

An example. To carry out comparative tests of the known and proposed cast iron compounds, six cast iron compositions are smelted - known at the middle level and proposed at the lower, middle and upper, as well as lower and higher than the upper damage to the content of components in the alloy,

The content of components in the investigated alloys are given in table. one.

Cast iron is melted in an acid lined induction furnace using steel scrap and pig iron in the mixture. To obtain the required composition of cast iron, ferroalloys of silicon, molybdenum, boron, chromium, iron sulfide are used.

Test specimens are poured into a dry land form. Before the gulf

The crystalline antimony, Cy2, and the electrothermal nitrated manganese are introduced into the liquid melt at 1450 ° C. The charge for obtaining iron of the required composition is calculated, based on the assimilation of silicon, antimony, manganese and nitrogen at a level of 85-90%, and molybdenum, boron and chromium 70-80%.

The abrasive wear tests were carried out on the friction machine by moving the emery cloth relative to the surface of the sample at a speed of 0.5 m / min at a relative pressure of 0.8 kgf / cm.

The hydroabrasive wear tests are carried out on an installation in which the sample rotates around a circle with a diameter of 300 mm in a liquid bath. The basis of the liquid bath is a 45% KOH alkali solution with the addition of silica sand, washed from the clay component, with a dispersity of 800 µm in an amount of 200 g / l of solution.

0

The fluidity of the alloy is measured by vacuum suction into a quartz tube with a diameter of 2.6 mm. The tendency of cast iron to foaming is evaluated visually as the ratio of the area of captivity to the full surface of the fracture.

Given in Table. 2 abrasive and hydro-abrasive wear of iron in an alkaline medium containing quartz sand, as well as indicators of hardness and linear characteristics show that the additional input of phosphorus and nitrogen into the composition of the iron significantly increases wear resistance and liquid-iron honor, and also reduces the tendency of iron to be foamed.

Claims (1)

The composition of cast iron undergoes laboratory tests and is used to manufacture the pump bodies of a unit for the chemical cleaning of castings obtained into shell molds. Wear-resistant cast iron containing carbon, silicon, manganese, sulfur, antimony, molybdenum, chromium, boron and iron, characterized in that, in order to reduce the tendency of pig iron to foaming, increase fluidity, abrasive and hydroabrasive resistance in alkaline media containing silica , it additionally contains nitrogen and phosphorus at the following ratio of components, wt.%: 3.0-3.5 five 0 0 five Carbon Silicon Manganese Sulfur Antimony Molybdenum Chromium Boron Nitrogen Phosphorus Iron 1.5-3.0 0.1-0.8 0.06-0.08 0.05-0.8 0.1-0.5 0.03-0.6 0.08-0.2 0.02-0.2 0.1-0.8 Else and about X l (N about " about, U S l n h 2 01 O P, with with t4 Famous Medium 311 Compiled by A. Barmykov Editor N. Gunko Tekhred L. Serdyukova Proofreader V. Girn to Order 4187/19 Circulation 604 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, Projecto st., 4 table 2 110 1.0 0.38