Steels for bearingproduction from Ovako

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Contents:Metallurgy of bearing steels

Steel grades

Research and developemnt

For bars, tubes, rings and wire rod,see brochures:Bar products from Ovako, also available in German, French,Polish, Finnish and Swedish

Seamless Tubes from Ovako, also available in German, French,Finnish and Swedish

Rolled and forged rings from Ovako

Wire rod for a broad scope of applications, also available inGerman, French and Polish

These brochures can be ordered or printed as PDF from our website.

vako is one of the world’s largest manufacturersof through-hardening bearing steel. We will maintain thisleading position as the bearing industry continuouslychallenges us to make further technical and logistical im-provements. As a supplier to most of the leading bearingproducers, we have acquired unique knowledge and ex-perience in this field.

Total ControlOvako is a fully integrated bearing steel producer.We control the whole chain of production, frommelting the steel through rolling to producing afinished component.

Our product range of tube, bar, ring and wireaccommodates all the main components of a rollingbearing. And we meet all the requirements specifiedirrespective of the type of steel used for rollingbearing manufacture.

Total PartnershipOur objective is to be a true partner with our customers,from both a technical and business point of view.

Our technical specialists are dedicated to workingclosely with those of our customers. This allows us tooptimise the use of steel both from a product and aproduction perspective. We can develop new and bettersteels, tailor-make products and improve machinabilityand heat treatment responses.

By co-operating with our key customers we are ableto establish long-term business agreements and customiselogistical and EDI solutions. We support them in theirglobal sourcing strategies and contribute with multipleproduct packages that keep administration to a minimum.We also have experience in joint cost- reduction activities.

Total QualityTotal Quality Management is a central concept withinOvako. All our activities aim at producing and deliveringproducts and services to fulfil customer’s needs. Ourquality policy and comprehensive quality assurance helpus to achieve the highest standards.

Ovako’s quality system conforms to ISO/TS 16949 andISO 9001. The company is also ISO 14001 certified.

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The demand for increased reliability of rolling bearings inservice is continuous. Bearings are expected to last longerand endure higher stress under adverse conditions. Thisposes higher demands on the steel used by bearingmanufacturers.

Our long-standing cooperation with the world’s leadingrolling bearing manufacturers has given Ovako a uniqueunderstanding of material development for rolling bearingapplications.

By optimising and making full use of these skills ineach production step we can achieve high quality bearingsteel with optimum mechanical properties. Each step mustbe controlled with a high degree of precision to minimisethe content of harmful non-metallic inclusions.

By controlling cleanliness carefully and through theuse of a number of key technologies,such as magnetic induction stirring andvacuum degassing in the the secondarymetallurgy, and controlled casting,it has been possible to increase thefatigue strength of our bearingsteels considerably.

The objective is to produce steel,which is optimised regarding properties,quality and economy.

Metallurgy of bearing steels

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Clockwise from top left:Steel melting, continuous casting,billet rolling and oxygen scarfing.

Steel making and billet productionOvako has four steel works, three of which have a scrap melting electric arc processand one blast furnace – oxygen converter process. Like most other producers ofbearing steel, Ovako uses scrap melting process as its basis for bearing steelproduction. The blast furnace – oxygen converter process is also a possibility tomake bearing steels.

Raw materialLike most other producers of bearing steel, Ovako uses scrap as its basic raw material.The selection and procurement of scrap is of great importance to the quality of theend product. For that reason we have high demands and tight control over the scrapwe use. Used ferroalloys and other additions, too, are carefully controlled.

MeltingThe melting process requires complete control of all parameters, from liquid raw meltto furnace control, so that the melt has the correct properties when it goes to thenext stage of production. At this stage, a number of the most important propertiesinherent in the cast are already fixed.

Secondary metallurgyThis process stage determines the final metallurgical quality, i.e. the final chemicalcomposition and the cleanliness of the steel.

The metallurgical unit operations in this part of the production process include:

• control of alloy content

• deoxidation (reducing the oxygen content and inclusion count in the steel)

• desulphurisation (reducing the sulphur content of the steel)

• degassing (elimination of other harmful gases)

• temperature adjustment (to reach the appropriate temperature for teeming).

• soft induction stirring

During this secondary metallurgy treatment the molten steel is stirred by an inductioncoil or by argon bubbling to create the best possible uniformity, removing oxideinclusions, sulphur and undesirable gases.

CastingThere are two ways to solidify bearing steels in Ovako: the traditional ingot castingand continuous bloom casting.

The uphill teeming of ingots is Ovako’s traditional casting technique. It createslarge forging reductions, so as to achieve the desired final quality requirements. Forsome bearing steel products it is the only accessible casting method. Uphill teemingensures a minimum of inclusions and a good surface finish. The design of the ingotmould has been optimised to reduce segregation in the steel during solidification,and during teeming the molten steel is shrouded by inert gas to protect it fromreacting with the air around it.

Once solidified, the ingots are stripped from the moulds and taken directly tothe soaking pits and brought to an adequate temperature before primary rolling.The soaking is introduced to avoid harmful segregation in the steel.

Ovako has also a very long experience in continuous casting. The first concastfacility was started up in 1965 at Imatra Steel Works. The bloom caster, which wasmodernised recently, represents the latest concast technology. The large bloom sizeof 370×310 mm results in a good deformation in rolling. Naturally all molten surfacesare protected and the mould stirring is standard Ovako practice.

The solidified blooms are hot charged into the reheating furnace for rolling. Thisbeneficial process provides clear advantages in surface quality and low level ofsegregations, resulting in good production economy.

Billet rollingThe entire metallurgical process at Ovako, from the steel melting to the finished billet,is carried out in a hot flow in order to minimise the risk of surface defects. Billets canbe surface conditioned by oxygen scarfing after the first stages of primary rolling, orby grinding.

Before the billets are transferred for secondary rolling, i.e. tube, bar, wire or rings,they are subject to magnetic particle testing testing, and, if needed, to grinding toremove the possible surface defects.

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Scrapping

Melting

Secondarymetallurgy

Rolling

Continuouscasting

Magnetic particletesting

Ingotcasting

Ovako mainly produces through-hardening steels forbearing applications, and is one of the world’s leadingcompanies in this segment. We also produce a significantquantity of carburising steel grades for this application.Listed below are some of our standard grades for bearingapplications.

Through-hardeningbearing steelsOvako specialises in high-strength through-hardeningbearing steels. These grades exhibit high fatigue and wear-resistance, good machinability, high hardness and gooddimensional stability. A hardness of 60-65 HRC can beachieved through martensitic hardening and tempering,making these steels ideal for bearing products. Thisdistinguishing property package is also suitable for othermarket segments and applications that have the same highquality requirements as the bearing industry.

100Cr6 type (SAE 52100)Used mainly for small and medium-sized bearing compo-nents. The 100Cr6 steel grades have high fatigue strengthand hardness, and good wear resistance. There are severaldifferent versions of this grade. For example:

Air hardening typeA steel grade specifically designed for air or gas quenching.By using gas cooling or air hardening it is possible to re-duce the amount of quench distortion. The use of quenchingmediums such as oil and salt can also be avoided.Hardenability corresponds to a bar with approx. Ø 40 mm(cooled in still air). The Ovatec® 677 series demonstratevery good mechanical performance, and is oftenrecommended for the most demanding applications.

Steel grades

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Designation acc. Ovakoto EN 10027-1 designation

100Cr6 803J Standard.

100Cr6 mod. F 803F With a controlled sulphur concontent for consistent machining properties.

100Cr mod. Q 803Q Isotropic properties and better fatigue strength due to higher cleanlinesslevels, and a finer size and distribution of non-metallic inclusions.

100Cr6 mod. Z 803Z Better cold forming properties due to reduction of the silicon content.

100Cr6 mod. D 803D Better machinability due to the higher sulphur content.

Designation acc. Ovakoto EN 10027-1 designation

70SiCrMnMo6-5 Ovatec® 677L Standard.

65SiCrMnMo6-5 Ovatec® 677Q Isotropic properties and better fatigue strength due to highercleanliness and a finer size and distribution of non-metallic

inclusions.

Through-hardening bearing steelsfor bainitic hardeningThese grades are used for bainitic hardened medium andlarge-sized bearing components. They all have a highfatigue strength, good toughness and excellent wear re-sistance. The through-hardenability corresponds to a ringwith wall thickness T, quenched in oil.

Through-hardening bearing steelsfor martensite hardeningThese grades are used for the martensite hardening oflarge- and medium-sized bearing components. They havehigh fatigue strength, high hardness and good wearresistance. The through hardenability corresponds toa ring with wall thickness T, quenched in oil.

Case-hardening bearing steelsOvako’s case-hardening bearing steels are adjusted to offergood machinability and minimal dimensional change afterhardening. The hard surface generated from case-hardening provides high fatigue strength and high wear-resistance, while the softer core gives the componenta high toughness. Ovako produces a number of case-hardening steels suitable for bearing applications.For example:

Definition of ringwall thicknessThe ‘‘T’’ section isdefined as the materialthickness that is thecontrolling factor inthe heat treatmentprocess, sometimescalled the rulingsection.

T

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Designation acc. Ovakoto EN 10027-1 designation

100CrMo7 824B Through hardenability corresponds to T< 20 mm (~ Ø 35 mm bar)

100CrMo7-3 825B Through hardenability corresponds to T< 30 mm (~ Ø 50 mm bar)

100CrMo7-4 826B Through hardenability corresponds to T< 50 mm (~ Ø 80 mm bar)

Designation acc. Ovakoto EN 10027-1 designation

100CrMnSi4-4 831B Through hardenability corresponds to T< 20 mm (~ Ø 35 mm bar)

100CrMnSi6-4 837B Through hardenability corresponds to T< 30 mm (~ Ø 50 mm bar)

Designation acc. Ovakoto EN 10027-1 designation

20MnCr6-3 126H Standard carburising steel with good toughness and highfatigue strength.

20NiCrMo2-2 152G Increased toughness due to a higher nickel content. Also availablewith normal sulphur content for better machinability.

17MnCr5 234K Controlled hardenability due to a tighter chemical composition.

18CrNiMo14-6 255G Excellent toughness and high fatigue strength, due to a highercleanliness specification and a high nickel content.

18CrMnMoNi9-5-5 277L Air-hardening carburising steel with high toughness and highfatigue strength.

18CrMnMoNi9-5-5 mod. 277Q Same as above, but higher cleanliness level.

Steel designation according to Quality C Si Mn S max. Cr Ni MoEN 10027-1 Ovako level % % % % % % %

100Cr6 803J BQ 0.97 0.25 0.35 0.015 1.50 - -

100Cr6 mod. F 803F BQ 0.97 0.27 0.35 0.015 1.50 - -

100Cr mod. Q 803Q IQ 0.95 0.30 0.30 0.002 1.50 - -

100Cr mod. Z 803Z BQ 0.97 < 0.15 0.35 0.015 1.45 - -

100Cr mid. D 803D BQ 1.02 0.30 0.35 0.025 1.50 - -

70SiCrMnMo6-5 677L BQ 0.70 1.55 1.40 0.015 1.10 - 0.25

65SiCrMnMo6-5 mod. Q 677Q IQ 0.65 1.50 1.40 0.002 1.10 - 0.25

100CrMo7 824B BQ 0.97 0.30 0.30 0.015 1.80 - 0.20

100CrMo7-3 825B BQ 0.97 0.30 0.70 0.015 1.80 - 0.30

100CrMo7-4 826B BQ 0.97 0.35 0.70 0.015 1.80 - 0.45

100CrMnMoSi8-4-6 827B BQ 0.97 0.50 0.90 0.015 1.90 - 0.55

100CrMnSi4-4 831B BQ 0.97 0.60 1.10 0.015 1.00 - -

100CrMnSi6-4 837B BQ 1.00 0.60 1.10 0.015 1.50 - -

26MnCr6-326 126H BQ 0.20 0.27 0.80 0.025 0.50 - -

20NiCrMo2-2 152G BQ 0.21 0.25 0.75 0.015 0.50 0.55 -

17MnCr5 234K BQ 0.16 0.25 1.15 0.035 0.95 - -

18CrNiMo14-6 255G PBQ 0.16 0.27 0.55 0.005 1.45 3.50 0.20

18CrMnMoNi9-5-5 277L BQ 0.18 0.35 1.30 0.030 2.20 0.50 0.50

18CrMnMoNi9-5-5 mod. Q 277Q PBQ 0.18 0.35 1.30 0.030 2.20 0.50 0.50

EN ISO 683-17 Ovako ASTM AFNOR DIN BS SAE SSNF A35-565:1970 17230:1980

100Cr6 803J A732 100 C 6 100 Cr 6 2 S.135 52100 2258

100Cr6 803F A732 100 C 6 100 Cr 6 2 S.135 52100 2258

100Cr6 803Q A732 100 C 6 100 Cr 6 2 S.135 52100 2258

803Z100Cr6 803D A732 100 C 6 100 Cr 6 2 S.135 52100 2258

677L677Q

100CrMo7 824B 100 CD 7 100 CrMo 7

100CrMo7-3 825B 100 CrMo 7-3

100CrMo7-4 826B100CrMnMoSi8-4-6 827B 100 CrMnMo 8

100CrMnSi4-4 831B A485

100CrMnSi6-4 837B 100 CM 6 100 CrMn 6

126H A534

20NiCrMo2 152G A322 20 NCD 2 805 A 20 2506

17MnCr5 234K 16 MC 5 16 MnCr 5 590 A 17

18NiCrMo14-6 255G A757 17 NiCrMo 14

277L

Average chemical composition

Comparable standards

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Steel designation according to Structure Hardness Rm (MPa) ReH (MPa) A5 (%) Z (%)EN 10027-1 Ovako

100Cr6 803 Martensite 61- 64 HRC 2300 1700 2 2

Bainite 58- 61 HRC 2300 2100 5 7

70SiCrMnMo6-5 677L Martensite 61- 64 HRC 2300 1700 2 2

65SiCrMnMo6-5 mod. Q 677Q Martensite 61- 64 HRC 2300 1700 2 2

100CrMo7 824B Bainite 58- 61 HRC 2300 2100 5 7

100CrMo7-3 825B Bainite 58- 61 HRC 2300 2100 5 7

100CrMo7-4 826B Bainite 58- 61 HTC 2300 2100 5 7

100CrMnMoSi8-4-6 827B Bainite 58- 61 HRC 2300 2100 5 5

100CrMnSi4-4 831B Martensite 61- 64 HRC 2300 1700 2 2

100CrMnSi6-4 837B Martensite 61- 64 HRC 2300 1700 2 2

26MnCr6-3 126H Case hardened 300-430 HB 980-1370 800-900 10-12

20NiCrMo2-2 152G Case hardened 300-430 HB 980-1370 800-900 10-12

17MnCr5 234K Case hardened 250-350 HB 880-1180 640 9

18CrMnMoNi9-5-5 277L Case hardened 350-370 HB 1100-1300 850-950 10-12

Typical mechanical properties

The properties correspond to typical values of core after hardening orcase-hardening.

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Cleanliness specificationsOvako’s continuous development of its steel making prac-tice over the last decade has made it possible to furthercontrol the oxygen and sulphur content in our products.The maximum inclusion levels have been significantlylowered, thereby ensuring steels with consistently highcleanliness and superior fatigue properties.In addition to bearing quality level (BQ) Ovako has threemore quality categories for bearing steels.CQ The Customer Quality level. Limits are defined

according to specific customer requests andagreed mutually.

PBQ The Premium Bearing Quality is intended formore demanding applications that require extraclean steel grades.

IQ The Isotropic Quality for applications requiringexceptional fatigue properties, and cleanlinesslevels comparable to Electro Slag Re-melt (ESR)and Vacuum Arc Re-melt (VAR) steels.

A-type inclusion. D-type inclusion.B-type inclusion. Titanium inclusion.

Typical microscopic inclusions

Fatigue testing equipment.

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The art of making steel requires an understanding of steeland an ability to predict what will happen to the steel invarious situations.

It is essential for Ovako as a supplier to the rollingbearing industry that we increase our knowledge andunderstanding about the steel and the products made fromit, thereby improving and meeting the increasing marketdemands and expectations. It is our explicit policy tocontinue to strengthen our position within this marketsegment, so it is not by chance that we are the companythat has developed and applied for more patents for bearingsteels and heat treatment variants than any other companyin the Western world. Ovako has developed and introducedmany new steel grades.

Neither is it by chance that we were the first in theworld to actively control the hardenability of the steelduring the production. We were also the first to achieveinclusion levels in conventionally produced steelscomparable with those of re-melted steels.

Today, our research and development activities areconcentrating on a greater understanding of steel andhow it performs from a metallurgical point of view andhow that affects the material properties. Our ultimatetarget is to optimise the steel performance for everyapplication and to come up with entirely new, costeffective material solutions. We are active in developingand improving our products. For instance, we areimproving tolerances on diameters, surface roughness,machinability and heat treatment properties.

Ovako co-operates closely with a number of researchinstitutes and universities to widen our competence andknowledge base so as to ensure success in ourdevelopment projects.

Research and development

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Material developmentOvako continuously strives to obtain a better knowledgeand understanding of the behaviour of our bearing steelmaterials through scientific research.

Fatigue testingFatigue testing is a useful tool for understanding and deter-mining the service life of bearing steels. At Ovako we havetest rigs for rolling contact, rotational bending and axialloading, which all generate valuable information about theproperties of fatigue. A steel grade’s fatigue property isdetermined by fatigue life testing in combination witha measurement of inclusion size and count.

SEM analysisOvako uses several ultra-modern Scanning Electron Micro-scope (SEM) for investigating microstructure, inclusioncharacteristics and crack properties. A Field Emission Gun(FEG) makes it possible to generate quality pictures at veryhigh resolutions. Analysing systems that uses back scattermapping in combination with X-ray spectroscopy are themost useful tool available for inclusion counting, providinginformation about inclusion composition and the sizedistribution. One microscope is also equipped with anElectron Back Scatter Diffraction (EBSD) detector, whichprovides information about the crystallographic orientationand material grain structure.

An Al2O3 inclusion. A study inside the inclusion.

A study of fatigued fracture surface in a bearing steel.

The SEM-microscopes are continuously used for manykinds of investigations.

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Ultrasonic testingImmersion ultrasonic testing is used as routine method ofquality control in many cases. The typical frequency rangewhen investigating bars and billets is 10 to 25 MHz.Immersion ultrasonic scanning of samples makes itpossible to see how different manufacturing stages affectthe occurrence of macro inclusions. This means that theproduct integrity is improved and changes in theproduction process can be followed.

Ovako has gone further, improving and developingimmersion ultrasonic testing methods by the use offocused, high frequency probes 25 to 80 MHz. This givesOvako the possibility to map both macro and mesoinclusions in our steel. Our ultrasonic test equipment givesus a quick and reliable testing tool for continuous researchand development.

Inclusion distribution diagram. Results from 80 MHz.A test piece scanned with a high-frequency (80 MHz) probe.A few larger inclusions can be seen in the C-scan image.The results of the evaluation are presented in a histrogram(left).

3.5

3.0

2.5

2.0

1.5

1.0

0.5

022 24 26 28 30 32 34

Size, d (µm)

No./mm2

High frequency ultrasonic scanning of a billet sample.

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Ovako is a leading European producer of long

special steel products for the automotive, heavy

vehicle and engineering industries. Production

consists of low alloy and carbon steels in the form

of bars, wire rod, tubes, rings and pre-components.

The company has 16 production sites and several

sales companies in Europe and the USA.

Total steel production is 2 million tonnes.

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SALES UNITS:

Finland:Ovako Bar Oy AbTeollisuuskuja 1FI-142 00 TurenkiTel: +358 (0)3 570 26 00Fax: +358 (0)3 570 26 02

France:Ovako France S.A.S.14, rue de MirandeFR-21000 DijonTel: +33 (0)3 80 54 15 15Fax: + 33 (0)3 80 50 14 67

Germany/Austria:Ovako GmbHPostfach 125540672 ErkrathTel: +49 (0)211-2504-0Fax: +49 (0)211-2504-244

Netherlands:Ovako Bar BeNeLuxBedrijvenpark Twente 295NL-7602 KK AlmeloTel: +31 (0)546-588 360Fax: +31 (0)546-588 366

Ovako Wire b.v.Postbus 3NL-2950 AA AlblasserdamTel: +31 (0)78 692 3100Fax: +31 (0)78 692 3192

Poland:Ovako Polska Sp. z.o.o.ILMET Building15 Jana Pawla II AvenuePL-00-828 WarsawTel: +48 (0)22 6976464 / 65 / 66Fax: +48 (0) 22 6976467

Russia:OOO OvakoOffice 1812Savelkinskiy proezd, d.4

124482 Zelenograd

MoscowTel: +7 (4)95 228 07 80Fax: +7 (4)95 228 07 81

United Kingdom:Ovako Ltd.Unit 2, Britannia ParkTrident DriveWednesbury WS10 7XATel: 0121 502 1010Fax: 0121 505 0019

USA:Ovako North America, Inc.1096 Assembly DriveSuite 312Fort Mill, SC 29708Tel: +1-803 1802 1500Fax: +1-803-1802-1501

PRODUCITON:

Sweden:Hofors Steelworks:Ovako Steel ABSE-813 82 HoforsTel: +46 (0)290 250 00Fax: +46 (0)290 250 25

Hällefors Rolling Mil:Ovako Steel ABSE-712 80 HälleforsSwedenTel: +46 (0)591 600 00Fax: +46 (0)591 606 06

Finland:Imatra Steel Works:Ovako Bar Oy AbTerästehtaantie 1FI-55100 ImatraTel: +358 (0)5 680 21Fax: +358 (0)5 680 22 11

Netherlands:Ovako Wire b.v.Postbus 3NL-2950 AA AlblasserdamTel: +31 (0)78 692 3100Fax: +31 (0)78 692 3192

www.ovako.com