CS214651B2 - Cast iron resisting the wear - Google Patents

Description

The invention relates to wear-resistant cast iron with high chromium content. Such types of cast iron can be used in the manufacture or repair of parts subjected to abrasion and abrasion and shock, such as, for example, cog teeth. wheeled and other excavators and diggers, working parts of hammer and jaw crushers, drilling tools for drilling sedimentary rocks, shovels' bulldozers and scraper blades. Said individual parts or their working parts can be produced or repaired using cast iron of the design composition, mainly by electrically remelting cast iron electrodes under the etrusk in molds whose walls and bottoms have a shape corresponding to the individual parts to be produced or repaired.

Various types of wear-resistant cast iron are already known. The widespread use of these types of cast iron in modern technology is conditional, firstly, on the low cost of diamond and sintered carbide cutting tools, such as tungsten, titanium and tantalum, and secondly on a sufficiently high notch toughness, which is particularly important and, thirdly, a sufficiently high abrasion resistance.

It is known to wear-resistant cast iron which is used for repairing worn parts by arc welding and which has this mass. composition: 2.5 to 3.5% carbon, 0.5 to 2.0% silicon, 0.1 to 1.0% manganese, 5.0 to 20.0% chromium, 0.4 to 1.5% boron, below 1.0% nickel, the rest to 100.0% iron and impurities.

Such cast iron is suitable for welding relatively thin layers on individual parts which, together with other metal parts and their alloys, are subjected to abrasion, for example, to welding on the faces of the exhaust spindles. valves in internal combustion engines ..

The use of such cast iron for the manufacture of individual parts or their working parts, which are subject to abrasion and impact wear, is ineffective because of its insufficient mechanical strength.

Furthermore, wear-resistant cast iron is known which is characterized by higher strength and can be used to manufacture new or repaired worn parts which are subject to abrasion or abrasion and impact. This cast iron contains by weight. concentration: about 3.0% carbon, about 1.0% silicon, about 1.5% manganese, up to 20.0% (chromium, about 0.5% molybdenum, the rest to 100% iron and impurities, see Petrov IV: Use of Wear-Resistant Welded Coatings to Extend the Working Life of Work Parts of Power Machines214651; Composite Volume “Science Results”, Edition “Welding”, - Publisher

Metallurgia, 1969.

However, the individual parts made using the cast iron described above are characterized by insufficient resistance to impact stress, which leads to the re-splitting of the outer layers and uneven shape deformations of these parts. The deviation of the shape of the parts from the shape prescribed by the design results in an increase in the dynamic load of the machines in which they are used and an increase in energy consumption. This circumstance causes these parts to be replaced before actual wear.

Of the known types of cast iron, cast iron containing, by weight:

carbon silicon manganese chromium nickel iron and impurities

2.5 to 3.3 % 2.8 to 3.5 % . to to 1.5 % 25 to 31 % ' • 3.9 to 5.9 %

remainder to 100.0%

This cast iron, welded in a thin layer on the parts made of high-grade steel and is resistant to abrasion and abrasion. However, due to the high silicon content and the coarse-grained microstructure, this cast iron is characterized by an increased brittleness in layers whose thickness is comparable to or greater than that of the steel part. For this reason, the use of such cast iron as a material for the production of workpieces, such as the tips of bucket teeth, bucket hammer noses and the like, can lead to breakage of them under impact load.

The combined impact stress and abrasion of such workpieces of work castings of the above cast iron further reduces their service life. -.

The purpose of the invention is to overcome the described drawbacks, ie. extend the life of wear parts cast from cast iron.

The object of the present invention was to reduce the silicon content and to produce a fine-grained microstructure of cast iron, which is characterized by increased resistance to impact wear and abrasion.

Given. The object is achieved by the wear-resistant cast iron according to the invention, consisting of carbon, silicon, manganese, chromium, nickel, iron and admixtures. The invention is furthermore characterized by the fact that it additionally contains titanium, said components being present in a concentration by weight of the following, namely carbon 3.9 to 3.5% silicon 9.6 to 1.5% manganese 9.8 to 1 5% chromium 23.9 to 27.9% nickel 3.9 to 3.5% ^! titanium. 9.6 to 1.9%

Iron and admixtures. rest up to 199,9%

By using silicon in mass. an amount of not more than 1.5% and the introduction of titanium significantly improves the wear-resistant microstructure of the cast iron; brittleness and increase resistance to impact wear and abrasion.

The wear-resistant cast iron of the chemical composition according to the invention can be produced in arc and induction furnaces with basic lining by melting a charge consisting of gray pig iron, steel waste with low (up to 9.3%) carbon, ferrochromium, ferromangan, ferrosilicon, nickel and ferrotitanium (or titanium metal).

Firstly, pigs of pig iron and steel waste are introduced into the electric furnace, the melting chamber of which has a temperature of approximately 1900 ° C, depending on the degree of melting of these components into the electric furnace. in small amounts (ranging from 15% to 25% of the calculated amount) is added with ferrochromium and nickel is added to the resulting chromium-containing melt. After melting of all the above components and after the melt has been homogenized, the lime additive in wt. an amount of about 5% by weight. the amount of charge, and the contents of the electric furnace are heated to 1439-59 ° C for 1 to 1.5 hours, until a thin slag is formed. In order to increase the flowability of the slag, it is possible to add to the furnace a mass of livestock. an amount of about 3% based on the amount of charge. Fepromangan is introduced into the metal melt and, after melting, ferrosilcium is optionally added and melted. After the slag has been removed, titanium metal or ferrotitanium is added to the furnace. The melt is homogenized and the wear-resistant cast iron is tapped off.

The produced cast iron is expediently cast into molds whose capacity corresponds to the volume of individual electrodes for the production of individual machine parts by electric remelting under slag. Necessary machine parts. can also be produced by direct casting of wear-resistant liquid cast iron into sand molds.

The wear-resistant cast iron articles of the chemical composition according to the invention are characterized by the following properties:

hardness, HRC 48 to 55 flexural strength,

MPa 696.27 to 735.49 deflection, measured at fracture of a sample of dimensions

349 X 49 X 29 me approximately 3.45 onwards. the abovementioned examples of wear-resistant cast iron compositions of the invention illustrate the invention in more detail.

Example 1

The wear-resistant cast iron consists of these components, the content of which is given by weight. concentration:

carbon 3,0% silicon 0,6% manganese 0,8% chromium 23,9 ° / n nickel 3,0% titanium 0,6% iron and impurities rest up to 100,0%

As an admixture to be checked, this cast iron is resistant to wear up to 0.05% phosphorus and up to 0.05 percent sulfur.

This cast iron is obtained from a batch containing the following components, the content of which is given by weight. concentration:

crude steel iron 12.8% steel waterfall 44.6% ferrochromium 35.2% ferromanganese 0.9% nickel 2.5% titanium 4.0%

Ferrosilicon may be used in an amount of about 2% by weight based on the total mass to adjust the chemical composition of this cast iron according to the results of rapid analysis of the melt samples. the amount of the aforementioned batch components.

The chemical composition of the above batch components is shown in Table 1.

Table 1 Chemical elements and their tips. concentration in charge components in%

charge components Fe O Si Mn Cr Ni Ti WITH P Cu As pig iron 93.15 4.0 2.2. 0.50 0.02 0.13 steel waste 98.48 0.18 0.12 0.5 0.2 0.15 - 0.05 0.04 0.2 0.08 ferrochrom 18.7 7.8 1.3 0.8 71.4 - - - -  - - ferromangan 18.89 7.0 1.9 73.0 - - 0.01 0.20 - - nickel - - - '- 99.99 -. - - ·, - - titanium -. -r- - - - .— 99.99 - - —- ferrosillcium 54.32 - 44.0 0, -6 0.5 ... - 0.03 0.05. . -

The amounts of the individual components of the charge required to melt the cast iron are calculated in a known manner, based on the capacity of the crucible of the electric furnace and the above-mentioned charge composition characteristics.

Wear resistant cast iron is obtained by melting in an induction furnace in a crucible containing 2.5 tons of quartz sand or ground ¹ quartzite. The electric power input of the furnace is 1300 kW.

The steel crucible and steel scrap are introduced in a calculated amount into the crucible of the induction furnace prepared in a known manner for melting, and these components are melted gradually over a period of 40 to 50 minutes, increasing the melting point up to 1430 ° C.

Ferrochromium is added to the melt five times in portions of 20% of the calculated total amount over 1 hour, each subsequent portion being added after melting the previous portion. The resulting chromium-containing melt is charged with a calculated amount of nickel and, after melting, the melt is maintained at a temperature in the range of 1430 to 1450 ° C for 1 to 1.5 hours. During this time, a lime additive of 5% of the total weight of the charge is added to the crucible to prevent attack of the crucible lining, and a fluorspar of 3% of the total weight of the charge is added to the resulting slag. The slag protects the melt from oxidation and contributes to its degassing.

up to 30 minutes before the end of the melting, the slag is removed, ferromangan is added to the melt in a calculated amount, and after melting, melt samples are taken for rapid analysis. According to the results of this analysis, the chemical composition of the melt is adjusted by adding ferrosilicon.

Immediately prior to discharge, titanium is added to the melt in a calculated amount. The melt is discharged into a pre-heated ladle.

Above, a particular example of a wear resistant cast iron with the above chemical composition is described. In view of the fact that the chemical composition of industrially used batches is characterized by data generally deviating from the data given in Table 1, wear-resistant cast iron melting requires rapid analysis of the chemical composition of the melt several times, use not only ferrosilicon, but also other ferrous alloys. Each time the sample is taken, the furnace is set aside for 10 to 20 minutes, ie for the time required for rapid analysis.

Wear-resistant cast iron is cast into well-dried clay sand molds to produce 10-15 mm thick slab and bar blanks, which are prepared by electrically remelting under the slag of the specimen to determine Rockwell hardness, flexural strength, the deflection of the specimen at break, the coefficient of relative abrasion resistance and the coefficient of relative abrasion resistance and impact.

214851

The hardness is determined by a known method in a Rockwell hardness tester on 10 mm thick plate samples.

The flexural strength is determined under static loading of cylindrical specimens of 30 mm thickness and 660 mm length. The distance between the prisms is 600 mm. The sample is loaded concentrated in the middle.

Deflection is measured on the same specimens after breaking. .....

The coefficient of relative abrasion resistance is determined in Chauort. A test apparatus by scraping 70 X 35 X 20 mm samples made of wear-resistant cast iron, chemical composition according to the invention, the known wear-resistant cast iron and annealed steel 45 serves as a comparative standard. The total of 45 contains 45 wt. concentration of 0.42 to 0.50% carbon, the remainder being iron and impurities. .

Granular grit with a grain size of 2 to 3 mm is used as an abrasive. Each test specimen is weighed, rubbed for 15 minutes at a load of 150 kp, then weighed again, and - taking the abrasion size of the test specimen of steel 45 as a unit of measure - a coefficient of relative abrasion resistance of abrasion is calculated according to. yr_ APst45 ^L ~ AP _VG 'where

AP _St 45 means the weight loss of the test specimen made of steel 45, a

AP _V g means the weight loss of the wear-resistant cast iron test specimen.

The coefficient of relative abrasion and impact resistance is determined by determining the condition of the bucket bucket teeth under industrial conditions. This caterpillar wheeled excavator has a bucket wheel equipped with nine single buckets, each bucket having 6 teeth with a working length of up to 100 mm.

For. The test is produced in three sets of test teeth, the working parts of which have been produced by the electric slag remelting of the wear-resistant cast iron of the chemical composition according to the invention and of the known cast iron with subsequent welding to steel shafts.

During each test cycle, 27 teeth of each type are consumed for cleaning work in quartz sandstone layers. The wear resistance is determined from the width of the worn surface at the trailing edge of each tooth. When the width of said surface reaches 35 mm, the worn tooth is replaced by a new tooth of the same type.

The coefficient ψ of the relative abrasion resistance and impact resistance is determined from the relation where

N _c means the number of teeth to be replaced with the workpieces known. cast iron, and

Nvg means the number of teeth replaced with wear-resistant cast iron workpieces of the chemical composition according to the invention.

The results of the individual tests are summarized in Table 2.

property and unit of measurement 'Table 2 values obtained in tests with cast iron resistant to known cast iron wear of the composition ......

according to the invention hardness, HRC flexural strength, MPa deflection of test specimen at fracture, mm coefficient of relative wear resistance by abrasion and impact up to 52. 48 to 50 ...

732.56 704.12

3.60 3.20

5.60 5.0

1.9 ¹ °

Example 2

The wear-resistant cast iron consists of the following components, the content of which is given by weight. carbon concentration 3.2% ^! silicon .1.2% manganese 1.1% chromium 25.0% nickel 3.2% titanium 0.8% iron and impurities rest up to 100.0%

As admixtures to be checked, the wear-resistant cast iron contains sulfur up to 0.05% and phosphorus up to 0.05%.

The cast iron of said chemical composition is prepared from a charge of these constituents, the content of which is given in wt. concentration:

crude steel iron 14.2% steel waste 41.5% ferrochromium 36.1% ferromanganese 1.1% nickel 2.8% titanium 4.4% '

According to the results of rapid analysis of the melt samples, ferrosilicon can be used in the amount of up to 2%, based on the total weight of the above batch components, to adjust the chemical composition of the wear-resistant cast iron.

Said batch components are characterized by the chemical composition shown in Example 1 in Table 1.

The wear-resistant cast iron is melted in an induction furnace similar to Example 1.

Plate and bar blanks of 10 to 15 millimeters thickness are produced from molten cast iron by casting into well-dried clay sand molds, from which the test specimens are prepared by electrical remelting under the slag to determine Rockwell hardness, flexural strength, break specimen deflection. , the coefficient of relative abrasion resistance and the coefficient of relative abrasion resistance and impact.

The tests are carried out similarly to Example 1. The test results are shown in Table 3.

Table 3 Property and unit of measurement obtained from tests with cast iron resistant to known wear cast iron of the composition according to the invention

hardness, HRC 50 to 53 48 to 50 flexural strength, MPa 709.02 704.12 deflection of the specimen at break, mm · 3.55 3.20 coefficient of relative resistance against abrasion 6.1 5.0 abrasion and shock 2,0 1.0 Example 3 To modify the chemical composition • resistant wear according to

Wear resistant cast iron consists of the following components, the content of which is given in weight concentration:

carbon silicon manganese chromium nickel titanium iron and impurities

3.5% 1.0%

1.5% 27.0%

3.5% 1.0 ·%:

remainder to 100.0%

As additives to be controlled, this iron contains up to 0.07% sulfur and up to 0.07% phosphorus.

The cast iron of said chemical composition is prepared from a charge of these constituents, the content of which is given in wt. concentration crude steel iron waste steel ferrochromium ferromanganese nickel titanium

14.8%

38.6%

37.6%

1.3%; 3.0% 4.7% of the results of rapid analysis of melt samples can be used up to 2% ferrosilicon based on the total weight of the above batch components.

The components are characterized by the chemical composition shown in Table 1 of Example 1.

The wear resistant cast iron is produced in an induction furnace similar to Example 1.

Plate and bar blanks 10 to 15 mm thick are produced from molten cast iron by casting to post-dried clay sand molds, from which the specimens are prepared by electrically remelting under the slag to determine the Rockwell hardness, flexural strength, break specimen deflection, coefficient of relative abrasion resistance and coefficient of relative abrasion resistance and impact.

The tests are carried out similarly to Example 1. The test results are shown in Table 4.

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Table 4 Property and unit of measure obtained in tests with cast iron with known wear resistant cast iron of the composition according to the invention

hardness, HRC 52 to 55 48 to 50 flexural strength, MPa 696.27 696.27 deflection of the specimen at break, mm 3.42 3.20 coefficient of relative resistance against abrasion 6.45 5.0 abrasion and shock 2.2 1.0

It will be apparent to those skilled in the art that wear-resistant cast iron may be characterized by a concentration of components other than those shown in the typical embodiments of the invention, provided that the particular concentration of the components does not exceed the nature of the invention and the scope of the desired patent protection.

Claims (1)

A wear-resistant cast iron consisting of carbon, silicon, manganese, chromium, nickel and iron, characterized in that it additionally contains titanium, said components being contained in the cast iron in the mass stated below. quantity, and I will invent it carbon 3.0 to 3.5% silicon 0.6 to 1.5% manganese 0.8 to 1.5% chrome 23.0 to 27.0% nickel 3.0 to 3.5% titanium 0.6 to 1.0% iron and admixtures remainder to 100.0% severografla, n. xirod 7, Moat