DE3201204C2 - "Use of a carbon-manganese steel for components with high strength and toughness with simple heat treatment" - Google Patents

Abstract

As a material for components with a cross-section from about 40 cm ↑ 2, which after hot forming by rolling, forging or pressing at final deformation temperatures or annealing temperatures of up to about 1000 ° C and subsequent cooling in still or moving air, possibly after controlled cooling, a ferritic pearlitic structure with about 5 to 20 ferrite, the remainder pearlite and a yield point or 0.2 limit of at least 580 N / mm ↑ 2 and an impact energy measured on ISO-U samples of at least 25 J, the use of a Steel proposed with analysis given within the following limit values with appropriate coordination of the individual substances with one another: 0.3 to 0.6 carbon, 0.2 to 0.6 silicon, 0.55 to 2.5 manganese, 0.05 to 0.2 Vanadium, 0 to 0.3 zircon, 0 to 0.2 niobium, 0 to 0.5 chromium, 0 to 0.5 nickel, 0 to 0.5 copper, 0 to 0.3 molybdenum, 0.01 to 0, 05 sulfur, 0 to 0.1 aluminum, 0.0005 to 0.005 boron, 0 to 0.04 nitrogen, less than 0.0 003 hydrogen, remainder iron and impurities from the melting process.

Description

0.43% carbon 0.30% silicon 1.80% manganese 0.08% Vanadium 0.14% chrome 0.046% sulfur 0.035% aluminum 0.001% boron 0.01% nitrogen

The remainder contains iron and impurities caused by the melting, as a material for components with a cross-section from 40 cm "'to 500 cm ² , which after hot forming by rolling, forging or pressing at band deformation temperatures or annealing temperatures of 900 to 950 C and subsequent cooling in still air longer than 60 minutes or in moving air shorter than 30 minutes a critical-pearl structure with about 5 to 20% ferrite.

[N / mm'l = 850 to 970 Ro .: [N / mm ") = 600 to 720 Λ M. = 17 to 20th Z [%1 = 56 to 57 Λ, [J] (ISO-U) = 26 to 28 , 5ZDW [N / mm ² ] = 400 to 420

Lair waste from the edge to the core of the largest cross-section of 500 cm ² 3% to 15%.

3. Use of a steel according to claims I or 2 as a material for components subject to alternating loads.

4 Use of a steel for the purpose according to claim 3 with the proviso that this / original-The invention relates to the use of a steel as a material for components with a cross-section from about 40 cm ² , which after hot forming by rolling,

ίο forging or pressing at Endverformungstemperaturen up to about 1000 "C or Glühiemperaturen up to about 1000 ^C C and subsequent cooling in still or moving air, if necessary after controlled cooling, a ferritic-pearlitic structure with approximately 5 to 20% ferrite, balance pearlite and a yield - or 0.2 limit of at least 580 N / mm ² as well as a notched bar, measured on ISO-U samples, vt .i at least 25 J.

From DE-PS 30 09 443 the use of a certain steel for components is known, which in addition to a high strength should also have a considerable toughness, namely enjoyed a notched impact work ^{at a yield or 0.2 limit of 580 N / mm 2} on DVM samples from 35 years without having to undergo an expensive heat treatment

-5 treatment would have to be subjected. As a composition, steel satisfying such conditions is used specified:

0.3 to 0.6%
0.65 to 1.2%
0.55 to 1.5%
0.05 to 0.2%
0 to 0.5%
0 to 0.2%
0 to 0.1%

carbon

silicon

manganese

Vanadium

chrome

sulfur

aluminum

0 to 0.04% nitrogen

The remainder is iron and impurities from the melting process.

Such a steel specified in said patent specification with relatively high proportions of vanadium within the analysis limits. When a bar rolled to 155 mm diameter is deposited in air, aluminum and nitrogen should have a 0.2 limit of 578 N / mm ^J , a tensile strength of 865 N / mm ² and an impact energy of 35 J measured on DVM samples.

In contrast, the object of the invention is. Steel for components with even higher strength at the same time still providing sufficiently high toughness, this being done by simply cooling the components in air after hot forming or an annealing process without further heat treatment should be.

As a solution to this problem, the use of steel according to the im Claim 1 indicated analysis proposed. Further advantageous refinements for this are shown in Characterized subclaims.

The invention is based on the following considerations shown below:

As the carbon content increases, the amount of steel in the steel and thus its strength wedge increases, Hardness and brittleness; up to about 0.6% carbon content also decreases its conversion rate at the same time on cooling from the final deformation temperature or annealing temperature. With up to 3% is manganese just like chromium Im 7-Elsen very soluble and increase! the strength without embrittlement by increasing the hardness of the Icrltantclles. the achievement of good earnings

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is necessary. In contrast to chromium, however, manganese forms far fewer carbides which impair the later machinability of the component and lowers the eutectoid point far less than chromium; Even with a relatively large proportion of manganese, the formation of cementite is avoided, which would particularly impair the subsequent processing of the component. Manganese also delays As mentioned above, a carbon content of up to 0.6%, the rate of conversion when the Component from the final deformation temperature or annealing temperature of around 1000 ° C, but at the same time lowered also all transition temperatures; arises within a large cooling rate range In addition, an almost constant perlilization with, depending on this, the same high strength, also for components with different cooling speeds caused by different wall thicknesses at different points. Due to the great affinity of manganese to impurities such as B. sulfur possible different longitudinal and transverse strength due to elongated structural interruptions caused by manganese sulphides and gas inclusions can occur when the the sulfur content through injection and evacuation processes in the pan treatment with appropriate additions through the formation of spherical impurities be bypassed. These affect the strength isotropy far less and still grant one of the Sulfur content dependent on good machinability of the component.

With the smallest additions of boron and / or small additions of molybdenum, the rate of conversion can be further slowed down by one or more room powers.

Micro additions of vanadium and. aluminum and possibly also effect of zirconium and niobium in an appropriate coordination with the nitrogen content through nitride and carbonitride formation as crystallization cores for fine grain formation, good distribution of the ferrite, as well as precipitation hardening in the ferrite Increase in the ratio of yield strength / breaking strength and also an increase in strength. Said process takes place with a component that is not influenced It is cooled in room air from a final deformation temperature or annealing temperature of around 1000 ° C, in Dependence on the wall thickness or wall thickness of the component with a certain speed that through light blowing, for example by means of an air shower, can advantageously be shortened.

Taking these considerations into account, a steel is to be used for a component whose carbon and manganese content is primarily determined according to the fact that the desired strength can be achieved, with manganese to a certain extent Scope can also be replaced by chrome. The fine-grain-forming and precipitation-hardening alloy components must also be among each other as well as with regard to the carbon and manganese hall. Furthermore, so much boron and / or Molybdenum should be added that with the dimensions and production conditions of the component adapted cooling conditions with slower or faster cooling In still or moving air such a politicization ceases as the desired one Toughness values demand it.

These catfish can be treated by a slight alloying with easily available, cheap additions with the simplest treatment method - since no expensive [facilities are necessary - and with extremely low energy ■: - Inexpensive components that can be easily processed further are created that meet the strength and toughness requirements of the task. These According to the invention, requirements can be met by using steel with the following analysis limits will:

0.3 until 0.6% carbon 0.2 until 0.6% silicon 0.55 until 2.5% manganese 0.05 until 0.2% Vanadium 0 until 0.3% Zircon 0 until 0.2% niobium 0 until 0.5% chrome 0 until 0.5% nickel 0 until 0.5% copper 0 until 0.3% molybdenum 0.01 until 0.05% sulfur 0 until 0.1% aluminum 0.0005 until 0.005 * , Boron Q until 0.04% nitrogen fewer as 0.0003% hydrogen

The remainder is iron and impurities from the melting process.

With a steel that meets the above conditions and is within the corresponding analysis limits

0.43%

0.30%

1.80%

0.08%

0.14%

0.046%

0.035%

0.001%

0.01%

carbon

silicon

manganese

Vanadium

chrome

sulfur

aluminum

boron

nitrogen

The remainder of iron and impurities from the melting process became shafts with a diameter of 250 mm from a final forging temperature of 550 C to 500 "C cooled in air and achieved the following strength values, which can be found in the table below:

Component diameter

[mm]

Coolant

Cooling time [min]

R _n , [N / mm- ¹ ]

Ro.2 [N / mm ² ]

A "[J] on ISO-U-Probe

O ₂ DW [N / mm *]

with 16 mm trial rod 0

blasted

Hardness H _s (edge)
Hardness H _e (core)

250 250

still moving air

Air (light blowing on the component)

75 25

858 968

600 718

20 17

57 56

27.5 26

400 420

248 282

240 246

From the table above it can be seen that in a component with a material proposed according to the invention even when it is cooled in still air very high strength and toughness values can be achieved, which can be achieved by specifically influencing the cooling

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- still smells a lot in terms of even better iVerte can be influenced. These values can be adjusted through more favorable alloy adjustments, especially the Klikrobeennaben can be further improved. The respected In any case, values show that with such a simply treated manganese steel it is practical Strength and toughness values as can be achieved with tempered steel, which the latter with the same : large dimensions (diameter 250 mm) to achieve the same strength and toughness values at least three times as high should be alloyed with alloy

elements such as chromium, nickel, molybdenum and others. Which, in their then necessary proportions, are in complete contrast to those used according to the invention Manganese steel would significantly worsen the later machinability of the component.

The steel proposed according to the invention provides these advantages particularly in the manufacture of components with larger cross-sections of about 40 cm ² and upwards, such as crankshafts or camshafts of internal combustion engines and the like, machine parts subject to alternating loads.

Claims (2)

32 Ol 204 up to 0.6% Steel with Patent claims: up to 0.6% carbon Using a up to 2.5% silicon 0.3 up to 0.2% manganese 0.2 up to 0.3% Vanadium 0.55 up to 0.2% Zircon 0.05 up to 0.5% niobium 0 up to 0.5% chrome 0 up to 0.5% nickel 0 up to 0.3% copper 0 up to 0.04% molybdenum 0 up to 0.1% sulfur 0 up to 0.005% aluminum 0.01 up to 0.4% boron 0 ■ than 0.0003% nitrogen 0.0005 hydrogen 0 little egg treatment of crankshafts or camshafts of internal combustion engines is used. Remaining iron and impurities caused by the melting process as material for components with a cross-section from 40 cm '', which after hot forming by rolling, forging or pressing at final deformation temperatures of up to 10U0 ° C or after annealing up to 1000 ° C and subsequent cooling in dormant or Moving air has a ferritic-pearlitic structure with 5 to 20% ferrite, the remainder pearlite and a Roj limit of at least 580 N / mm ² as well as an impact energy, measured on ISO-U samples, of at least 25 J. 2. Use of a steel according to claim I with the proviso that this