RU1780890C - Two-layer mill roller - Google Patents

Description

1

(21) 4909997/27 (22) 11.02.91 (46) 12/15/92. Bull.Mg46

(71) Ukrainian Research Institute of Metals

(72) E.N. Vishnova, V.K. Parfenyuk, V.V. Korobeinik, V.P. Prikhodko, N.A. Krupa, V.A. Movov, V.I. Komlkov and S .P. Pavlov (56) Japanese Application No. 59-225806,

class B 21 B 27/02, 1984.

Author's certificate of Czechoslovakia No. 218329, cl. B 21 B 7/00, 1985.

U.S. Patent ISfc 3997370, CL 148-12R, 1976.

(54) TWO-LAYER ROLLING SHAFT (57) Use: cold rolls for rolling mills. SUMMARY OF THE INVENTION: the outer working layer of a rolling roll is made of alloyed cast iron composition, wt.%: C 3.0-3.3; Si 1.0-1.5; MP 0.3-0.6; N1 2.0-2.8; Cr 0.2-0.4; Cu 0.5-1.5; Md 0.001-0.05; Mo 0.2-0.4; Fe the rest. The core and neck of the roll are made of cast iron composition, wt.%: C 3.0-4.0; Si 1.5-2.0; MP 0.2-0.4; Cr 0.1-0.3; Md 0.02-0.06; Fe the rest. The total ratio of graphitizing and carbide forming elements of the material of the outer layer to the core material is 1.45-1.6. 3 tab.

The invention relates to metallurgy, in particular, to the search for materials for rolls of cold-rolled sheet mills, characterized by a high level of strength and operational properties of the roll barrel, good machinability of the neck of the rolls with high cracking resistance, intended for use in the manufacture of massive products operating in conditions of intense abrasion.

A known roll with drive necks of mild steel and a method for its manufacture are known.

Viscous steel is used for the ends of the necks that are joined to the neck by welding. Preheating is done by inductors. The end of the roll is pressed to the neck when welding with a hydraulic jack. The material of the outer layer is adamite or alloyed cast iron. Core Material - Cast Iron

(L

WITH

with a spheroidal graphite chemical composition, wt.% 1:

Carbon

Silicon

Manganese

Nickel

Chromium

Molybdenum

Iron

Quite

3.0-3.8 1.5-2.5 0.4-1.0 2.0

0.1-1.0 0.2

The rest is difficult exercise

00

about

00

what about

the welding process and a significant heat affected zone cannot provide the required quality level for small diameter rolls, and the material of the roll barrel does not meet the requirements for rolls of cold-rolled sheet mills.

Known cast iron metallurgical rolls for hot rolling of plate, chemical composition, wt.%: Carbon 2.8-3.5

Manganese 0.6-1.2

Silicon 0.8-1.4

Phosphorus 0.05-0.25

Sulfur0.001-0.03

Magnesium 0.02-0.08.

In addition, cast iron must have at least four of the following alloying elements, wt.%:

Chrome 0.05-0.5

Nickel 3.2-4.0

Molybdenum. 0.03-0.6

Copper 0.5-1.0

Vanadium 0.03-0.2

IronOther

Rolls made of such cast iron are characterized by an insufficient level of properties and hardness required for cold rolling rolls. This is explained by the fact that with such a composition, perlite bainite base and granular graphite are realized. Known multilayer cast iron rolls for rolling at temperatures up to 1800 ° C the following chemical composition of the outer layer, wt.%:

Carbon 3.3-3.7

Manganese 0.35-1.25

Silicon, 1.0-2.0

Nickel 3.75-5.75

Chrome 0.75-1.35

.Molybdenum 0.4-1.1

Magnesium 0.3-0.08

IronOther

Rolls of such materials are characterized by high heat resistance, which is necessary for hot rolling of products. However, for the work of the rolls during cold rolling, it is necessary to obtain a bainitic carbide structure, which will ensure high wear resistance with a sufficiently high hardness.

The closest in technical essence to the claimed is a multilayer bandage roll with a caliber made by centrifugal casting, the outer layer of which has a chemical composition, wt.%:

Carbon 3.0-3.7

Silicon 1.5-2.5

Manganese 0.2-1.0

Nickel 0.7-3.0

Chrome. 0.1-0.5

Molybdenum 0.1-1.0

Magnesium 0.02-0.1

IronOther

inner layer, wt.%:

Carbon 2.8-3.8

Silicon 1.8-2.8

Manganese 0.1-1.0

Nickel 2.0

Chrome 0.4

Molybdenum 1.0

Magnesium 0.02-0.1

IronOther

A disadvantage of such a bandage is the inapplicability of the transfer of material for hot-rolling rolls of high-grade 5 mills to rolls of cold-rolled sheet mills due to significant adhesion processes leading to premature roll exit from the system in bulk.

0 The aim of the invention is to prevent breakage of the necks of the rolls, to improve their machinability, to reduce the adhesion processes, and to increase the reliability of the rolls.

5 In order to achieve this goal, copper is additionally introduced into the cast iron of the outer layer in the following ratio of components, wt.%:

Carbon 3.0-3.3

0 Silicon 1.0-1.5

Manganese 0.3-0.6

Nickel: 2.0-2.8

Chrome 0.2-0.4

Copper 0.5-1.5

5 Magnesium .001-0.05

Molybdenum 0.2-0.4

Iron the rest,

the core contains elements in the following ratio of components, wt.%: 0 Carbon 3.0-4.0

Silicon 1.5-2.0

Manganese 0.2-0.4

Chrome0.1-0.3

Magnesium 0.02-0.06

5 Iron Else,

moreover, the total ratio of graphitizing and carbide-forming elements of the outer layer to the core is 1.45-1.6.;.,

0 The proposed material for the outer (working) layer of the rolls is characterized by high resistance to welds, and internal to cracking of the necks, which increases the reliability of the rolls. 5 According to the data available from the applicant, in the known solutions there are no features similar to those that differ from the prototype of the claimed solution, which allows us to conclude that there are significant differences with criterion 0.

The selected limits for the content of chemical elements in the proposed cast iron are provided by the following arguments.

Additionally introduced into cast iron for

5 working layer of copper rolls in an amount of 0.51, 5% allows to increase hardness, wear resistance. AND VISCOSITY, DECREASE AN INCLINATION

adhesion processes, which is very important for cold rolling rolls. This is due to the fact that one of the main defects

The cause of premature failure is billet, which accounts for 50% of the total yield of rolls due to defects. The introduction of copper in an amount of up to 1.5% makes it possible to limit the content of scarce and expensive elements: Ni not higher than 2.8% and molybdenum 0.4%, respectively, which indicates the efficiency of using copper as a substitute for them. The increase in the operational properties of the metal and the resistance to broths are associated with the hardening of the solid solution a-Pe with copper. In this case, the precipitation of copper occurs on the a-Fe slip planes, which makes their mutual displacement difficult, thereby preventing the metal from setting. An increase in wear resistance during copper alloying is achieved by increasing the amount of the pearlite component, lowering critical points and stabilizing austenite in bainitic and martensitic nodular cast irons, and isolating cuprous inclusions on the surface. Thus, in order to increase the operational properties, it is necessary to introduce copper into high-carbon alloys in an amount exceeding the limits of its solubility at operating temperatures.

The introduction of up to 0.5% Cu does not affect the operational properties of the rolls,

The introduction of copper in excess of 1.5% leads to a decrease in the thermal endurance of cast iron.

In addition, in the proposed cast iron, the combined effect of copper, nickel, and molybdenum should be considered, since copper serves as a partial substitute for nickel and molybdenum. Moreover, their total content is in the range of 2.7-4.7%.

Copper, nickel and molybdenum, reducing the free energy of the mixture of austenite and graphite, increase the thermodynamic potential for direct release of graphite. In addition, they provide the formation of a stable structure in the intermediate region, contributing to an increase in strength properties, hardness, thermal endurance and increase in the stability of the carbide phase, grinding of graphite incorporation and austenite decomposition products.

The presence in the cast iron of copper, nickel and molybdenum in amounts of less than 0.5, 2.0 and 0.2%, respectively, leads to the formation in the castings of a structure consisting of coarse austenite decomposition products of varying degrees of dispersion, which significantly embrittle the material, reduces the level

mechanical properties, increases anisotropy and reduces thermal endurance.

With an increase in the content of copper, nickel and molybdenum in amounts of more than 1.5, 2.8 and 0.4, the level of mechanical properties of cast iron, respectively, decreases, which is associated with a violation of the optimal ratio of graphitizing and carbide-forming

0 elements, the shape of graphite inclusions deteriorates, they enlarge and branch, which also affects the thermal endurance of the material.

5 When the content of carbon and silicon is less than 3.0 and 1.0%, respectively, coarse carbide inclusions appear at the grain boundaries in the structure of castings, which reduces the plastic characteristics and thermal endurance, which contributes to the chipping of the working layer of the roll during operation. An increase in the carbon and silicon contents over 3.3 and 1.5%, respectively, leads to flotation of graphite, which

5 is especially characteristic of massive castings, as a result of which there will be an uneven distribution of hardness and, consequently, wear over the cross section of the roll. In addition, increasing the content

0 silicon over 1.5%, due to its tendency to eliminate, impairs strength characteristics.

Manganese, chromium and molybdenum are carbide forming elements. However

5 in the claimed composition as a result of the interaction of graphite-forming elements. (silicon, nickel and copper), austenite is combined with carbon, as a result of which the manganese, chromium and molybdenum in the selected quantities are mainly used not for the formation of an excess carbide phase, but for alloying, which improves the mechanical properties of cast iron and increases the stability of the carbide phase in conditions x

5 thermal cycling that occurs during the operation of the rolls.

It was found that the optimum manganese content is 0.3-0.6%. With a manganese content of 0.3%, a ferritic component may appear, hardness may decrease and an inhomogeneous structure may form, which contributes to intensive wear during operation. Manganese content of 0.6% reduces carbon activity

5 and a decrease in the number of graphite nuclei, which creates the conditions for the formation of excess cementite and a decrease in ductility.

The introduction of chromium in an amount of 0.2% is not enough to increase hardness and

strength of cast iron, and an increase in its content of over 0.4%, especially in the presence of other carbide-forming elements, contributes to the formation of a coarser carbide phase, prone to chipping under thermal cycling and high specific pressures.

To produce spherical graphite, cast iron is modified with magnesium in an amount of 0.001-0.05%. When the magnesium content is less than 0.001%, spherical shape of graphite is disturbed and lamellar precipitates appear. An increase in the magnesium content above 0.05% helps to increase the stability of structurally-free cementite, worsens the shape and distribution of non-metallic inclusions, without having a positive effect on the properties of cast iron.

To ensure these properties, the composition of cast iron must be stabilized so that the total ratio of graphitizing and carbide forming elements of the outer layer to the core is 1.45-1.6.

In this respect, a strong working layer is achieved, with a viscous core and roll necks, which increases their service life.

With a total ratio of graphitizing and carbide-forming elements of the outer layer to the core of 1.45, due to the insufficient number of graphitizing elements in the metal of the outer layer, a tendency to adhesion processes is not reduced, which leads to a reduction in the service life of the rolls. When the total ratio of graphitizing and carbide-forming elements of the outer layer to the core 1,6 is formed, a large number of graphitizing elements are formed in the metal of the outer layer of the rolls, which does not provide sufficient wear resistance and, therefore, reduces their reliability.

The roll is made as follows — first, molten metal is poured into the rotating mold in a centrifugal casting unit and the outer layer is formed, then, after the inner surface of the outer layer has hardened, the core of the roll is filled.

Since the rolling rolls operate under thermocyclic conditions and are prone to adhesive processes, the resistance to chipping of materials was assessed based on the metal's tendency to weld.

In order to determine the mechanical and operational properties of the proposed roll, 6 alloys were cast with boundary and optimal ratios of ingredients for the working layer and core. For

For comparative analysis, 4 alloys with boundary and optimal ratios of alloys according to the prototype and 1 alloy of forged steel 9 X2 of current production 5 were cast (Table 1).

Each alloy was smelted in a 200 kg induction furnace. The following materials were used as charge materials: steel scrap, FeSi (75%), FeMn (45%), FeCr (72%), granulated nickel, hydrolyzed copper. Rolls were cast on a centrifugal horizontal machine 552-2. From the obtained alloys were made samples that were tested for hardness; strength, heat resistance, 5 workability, the amount of wear, the tendency to adhesive processes were determined.

Thermal stability tests were carried out by thermal cycling the samples at temperatures of 600 fc200C until the first cracks appeared, which reflects the conditions of heating and cooling during operation of the rolls on sheet mills.

The machinability of the test alloys after annealing was evaluated by drilling 5 templates with a thickness of 20 mm. For standard drills, the axial thrust during drilling was determined by the formula

Foc 0.195 (HB) f 0.8o + 90.02, where HB is the Brinell hardness of cast iron; 0 f-feed, mm per revolution;

D is the diameter of the drill, mm

Providing a constant axial force, diameter of the material of the drill, the number of spindle revolutions, feed per revolution f - 5 is the criterion for the workability of the material. When drilling each template, new drills with a diameter of 10 mm made of steel R 6M5K5 were used. Drilling was performed without cooling the tool, fixing 0 the time the drill passed through the template and calculating the feed rate per revolution. Each template was drilled at least 5 times,

As shown by the data of the tests (Table 2), the obtained alloys (1-4) 5 were characterized by the following level of properties: the metal of the outer layer — ultimate strength in bending of 900–950 N / mm2, impact strength — 9–10 J / cm2, heat resistance

-1900-2150 cycles to failure, hardness 82-85 NZD. Metal of the core and necks

-bending strength - 480-550 N / mm v / dar viscosity 13.8-15.0 J / cm. heat resistance 2900-2980 cycles to failure, hardness 300-311 HB.

5 When the boundary values of the ingredients and the ratios of carbide-forming and graphitizing elements of the outer layer and core are exceeded, the level of mechanical and operational properties is lower.

Based on the data presented, we can conclude that the claimed rolling roll (options 1-4) compared with the prototype (options 9-11) will increase the heat resistance of the metal of the necks of the rolls by 1.6 times, impact strength - by 1, 8 times with improved machinability 1.25 times, which helps to prevent breakage of the necks.

The effectiveness of the claimed material, in particular, by its propensity for adhesive processes (welding), the amount of rolled metal per installation, and wear was checked under experimental industrial conditions. For testing, rolls were cast whose composition corresponded to the proposed rolls, prototype rolls, and forged steel rolls of current production.

The tests were carried out under conditions similar to the serial production of rolled products by specific pressure on the roll, speed, rolling temperature, gauge, roll cooling mode. Checks were made to rolls occupying the same position in the stand. The depth of the working layer is 20 mm. Regrinding of all rolls was carried out at a constant mode. After being removed from the cage, the rolls were cooled in air. The ambient temperature was positive. Grinding removal was calculated taking into account the barrel wear.

The test results for options 1-3 and 8, 9, 12 are presented in table 3. The results given in the tables are confirmed by the test report.

The best results were obtained on rolls of the proposed composition (option No. 2), where metal wear is 2.0 times less than that of the prototype metal, and 2.3 times less than forged steel rolls due to a decrease in the amount of weld, which and in turn led to an increase in the number of rolled metal by 1.3 times compared with the prototype and 1.4 times compared with steel forged rolls due to the optimal structure. Moreover, for 30 installations, the working layer was used by 65%.

With the proposed chemical composition of cast iron according to options 1 and 3, wear and tear is 1.6 and 1.9 times lower than that of the prototype, and 1.9 and 2.1 times lower, respectively, compared to forged steel, the amount of rolled metal is 1 3 times compared with the prototype and 1.3-1.38 times more compared to forged steel rolls of the current production, respectively.

When you go beyond the boundary values of the ingredients (option 8) at 27 settings, wear is 1.14 times, and the amount of rolled metal is only 1.04 times more compared to option 1, 2 at 20 settings and slightly differs from the prototype (option 9 )

Thus, according to the data of the tests of the claimed invention in comparison with the prototype has the following advantages:

the heat resistance of the metal of the necks of the rolls is 1.6 times higher;

the impact strength of the metal of the necks of the rolls 5 is 1.8 times higher;

the workability of the necks is 1.25 times lighter;

Claims (1)

the amount of rolled metal per installation is 1.2-1.3 times higher; 0 roll service life is 1.3 times more. The inventive roll is of significant interest to the national economy, as it allows to increase the rhythm and productivity of rolling mills, to reduce the consumption of rolls, to ensure the yield of metal of higher grades, reduce the complexity of manufacturing rolls and reduce the consumption of fuel and energy resources . 0 Claims A two-layer rolling roll, the working layer of which is made of alloyed cast iron containing carbon, silicon, manganese, chromium, nickel, magnesium, molybdenum 5 and iron, and the core and necks are made of cast iron containing carbon, silicon, manganese, chromium, magnesium and iron characterized in that, in order to prevent breakage of the necks of the rolls, reduce adhesion processes, as well as increase the reliability of the rolls, the working layer additionally contains copper in the following ratio of components, wt.%: Carbon 3.0-3.3 5 Silicon 1.0-1.5 Manganese 0.3-0.6 Nickel: 2.0-2.8 Chrome 0.2-0.4 Copper 0.5-1.5 0 Magnesium .001-0.05 Molybdenum 0.2-0.4 Iron the rest, and the core contains elements in the following ratio of components, wt.%: 5 Carbon 3.0-4.0 Silicon 1.5-2.0 Manganese 0.2-0.4 Chrome0.1-0.3 Magnesium 0.02-0.06 Iron the rest, moreover, the total ratio of graphitizing and carbide-forming elements 9 w 11 12 950 940 900 850 830 800 820 780 790 79 $ 10.5 9.5 9.0 10.0 8.5 8.0 3: 8.0 7.9 8.1 1000-1500 20-30 Suggested composition 1EOO8255v13.829203009.45 10 2200 8ft52013.529803079.910 21,008 $ 50,014,829003119,710 21508348015.029703009,310 19008046010,026902789,0ID2 1550811.509.727602708.7U 187030.4309.027502858.910 1800824408,828002628,810 Bae about the "composition (prototype) 1700704509.518003517,510 165072 5008.3i8603637,610 1720714606.019003597,810 Forged Roller Current Production 9X2 Steel 150095-D8600-700 12-161000-1200 30-35 HSD the outer layer to the core is 1.45-1.6. T in 6 l and u a 1 Table 2 b l c a 3 Continuation of Table 3