Steeltec ETG® 25

2

Steel for that competitive edge

Steel has been one of the most impor-

tant materials for many centuries. We

produce it in grades and qualities which

enable our customers to succeed in

an increasingly harsh competitive envi-

ronment. Steel from Steeltec is used

wherever precision parts are required to

satisfy highly stringent demands, millions

of times over, both safely and reliably,

for years on end. Parts which have to be

produced both efficiently and at a very

low cost. While the requirements placed

on steel may vary, our past, present

and future passion for continually optimis-

ing the way we fulfil them remains

unchanged.

ETG® 25: Cold steel with mechanical pro-perties similar to strength class 8.8 without thermal treatment:

– good cold formability– good machinability– good weldability

Optimum properties as drawn, with a wide range of uses. Steeltec We put energy into steel

>

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ETG® 25 to reduce your costs

and enhance your competitiveness

Rising costs and the current competitive

situation make it essential to exhaust all

conceivable means of reducing produc-

tion costs today. And a key contribution

can be made here by employing ˝ready-

to-use˝ steels which ensure the specified

properties are achieved in the finished

part without need for elaborate heat treat-

ment. ETG® 25 is a material which

offers good cold formability, despite the

high initial strength of the material as

received (similar to strength class 8.8).

This then eliminates the need for heat

treatment and elaborate secondary opera-

tions, such as straightening, cleaning and

discards.

As a high-strength, cold-formable

special steel, ETG® 25 exhibits

the following unique combination

of properties:

– mechanical values similar to strength

class 8.8 as drawn, according to

EN ISO 898-1:1999

– ferritic-pearlite structure

– consistent properties over the entire

cross-section and the full size range

– low residual stress

– high fatigue strength

– high abrasion resistance

– good cold forming properties

– good bendability

– problem-free surface treatment

– good machinability

– no heat treatment required

– good weldability

In short: ETG® is a high-strength

special steel with excellent

cold forming, bending and welding

properties.

From scrap to the final bright product,

ETG® 25 is manufactured entirely within

our own production plant.

The short process chain gives

high product quality, resulting from

a number of decisive factors:

– decades of experience in manufacturing

and application

– expert manufacturing competence in

steelmaking, rolling and bright drawing

– stringent checks during production to

ensure consistently high quality within

very close tolerances

– state-of-the-art testing procedures

at all stages of processing, including

100% surface crack testing as

standard.

5

Comparison of component costs ETG® 25/35B2

10

8

6

4

2

0 Material Cold forming Quenching and tempering Straightening

ETG® 25 35B2 Total ETG® 25 Total 35B2

Product rangeETG® 25 is available in the following finishes and sizes:

Steel category Process Size range mm ToleranceETG® 25 drawn ≥ 4.0 – ≤ 28.0 h9 ground ≥ 4.0 – ≤ 28.0 ≥ IT6

– bar lengths: 3–6.5 m– colour coding: yellow end-face – other categories to meet special requirements

(e.g. mechanical properties) are available to special order. Regular sizes are available from stock.

We shall be very happy to answer your questions concerning the use of ETG® 25.

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Mechanical properties as drawn (guide values)

StaticDimensions Ø mm ≤ 16 > 16Proof stress Rp0,2 N/mm2 ≥ 660 ≥ 660Tensile strength Rm N/mm2 800 – 950 830 – 950Ultimate elongation A5 % ≥ 12 ≥ 12Reduction of area Z % ≥ 45 ≥ 45Hardness HV10 230 – 300 255 – 336Notched impact energy AvRT ( ISO-U) J ≥ 30 ≥ 30

DynamicTension/compression σzdw N/mm2 ap. 360Reverse bendingSpecimen without notch σbw N/mm2 ap. 390Specimen with notch αk=4,0 σbw N/mm2 ap. 125Torsional reversal τ tw N/mm2 ap. 175

Chemical analysis, melt analysis in % by weight

Element C Si Mn P Smin. 0.24 0.10 1.20 0.02max. 0.29 0.30 1.50 0.04 0.04

Killed with aluminium or agents having a similar effect. The analysis complies with SAE 1527, comparable with 28Mn6 (1.5065).

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8

9

ETG® 25 for formed parts

Cold forming

As with all finally-formed parts, care

must be taken with upset parts to

ensure that forming is conducted in the

same direction as the load that will be

acting on the part when in service. If the

load acts in the opposite direction, a

reduction in the proof stress may result

(Bauschinger effect). The strength

and hardness are unaffected. Subsequent

tempering at 350 °C can reverse this

effect. The proof stress then returns to

its original value.

Flow curve

established in the cylinder upset test

(Ø 10 x 16 mm), Range ± 50 N/mm2.

The special production process gives

ETG® 25 non-standard flow properties.

The material’s high proof stress means

that relatively high forming forces are

required even for low degrees of forming.

Contrary to the case for conventionally-

produced steels, the flow resistance

remains constant up to high degrees of

forming.

Flow curve ETG® 25

1250

1120

1000

900

800

710

0.1 0.125 0.16 0.2 0.25 0.315 0.4 0.5 0.63 0.8 1.0 1.25 1.6

Degree of forming �

Yie

ld s

tres

s kf

[N

/mm

2]

1,4 0,9

1,0

1,1

10

Mechanical properties after cold

forming

Mean values for ETG® 25 as a function

of the degree of forming and upset by

comparison to conventionally-produced

steels.

Proof stress Rp0,2 [N/mm2]

1500

1000

800

600

400

200Degree of forming � 0.1 0.2 0.4 0.6 0.8 1 1.5 2Degree of upset ε [%] 18.1 32.9 55 79.5 86.5

Case-hardening and quenched and tempered steelsCold-forming steels

ETG® 25

Tensile strength Rm [N/mm2]

1500

1000

800

600

400

200Degree of forming � 0.1 0.2 0.4 0.6 0.8 1 1.5 2Degree of upset ε [%] 18.1 32.9 55 79.5 86.5

Case-hardening and quenched and tempered steels

ETG® 25

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Hardness HV10

360350340330320310300290280270260250240230220210200

190 180Degree of forming � 0.1 0.2 0.4 0.6 0,8 1 1.5 2Degree of upset ε [%] 18.1 32.9 55 79.5 86.5

Case-hardening and quenched and tempered steelsCold-forming steels

ETG® 25

Reduction of area Z [%], elongation A5 [%]

100

0Degree of forming � 0.1 0.2 0.4 0.6 0.8 1 1.5 2Degree of upset ε [%] 18.1 32.9 55 79.5 86.5

60

40

20

10

6

4

Case-hardening and quenched and tempered steels. Cold-forming steels

ETG® 25

Elongation A5 [%]Case-hardening and quenched and tempered steelsCold-forming steels

ETG® 25

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ETG® 25 for cold-profiled threaded

bolts with higher fatigue strengths

Non-cut formed threads

Non-cut formed threads have a strain-

hardened screw root with compressive

internal stresses.

The proof stress is thus somewhat

lower and the fatigue strength somewhat

higher than for the starting material.

Fatigue stressing as a function of the

maximum endured stress amplitude ± σA

without fatigue fracture

– stress cycle >2•106

– M 12 threaded connection

– bolts, ETG® 25, rolled thread

– nut, DIN 934 class 8

Fatigue strength of ETG® 25

Pre

ssur

e

|

Trac

tion

[N/m

m2]

+σA

-σA

Rp0,2+700

+600

+500

+400

+300

+200

+100

0

-100

-200

100 200 300 400 500 600 700

Mean stress σm [N/mm2]

13

Permitted static stressing on thread

120

110

100

90

80

70

60

50

40

30

20

10

0

5 6 8 10 12 16 20 30 40

Nominal thread diameter [mm]

End

ured

str

ess

amp

litud

e ±

σA [

N/m

m2]

ETG® 25 M 12

Thread, rolled and quenched and tem-pered 8.8 to 12.9

ETG® 25 M 16

Characteristic values for threaded bolts

RT RT -20 °C -20 °C -40 °C -40 °CSize mm ≤ M16 > M16 ≤ M16 > M16 ≤ M16 > M16Tensile strength Rm N/mm2 ≥ 810 ≥ 830 820 840 830 850Proof strength Rp0,2 N/mm2 ≥ 660 ≥ 660

At elevated temperatures (typical values)established on turned bolts +100 °C +200 °C +300 °CTensile strength Rm N/mm2

815 815 800Proof stress Rp0,2 N/mm2 665 665 635Elongation at fracture A5 % 13 12 18

Static stressing of threaded bolts in

ETG® 25 with a rolled thread. Testing in

accordance with EN ISO 898-1:1999,

on the threaded bar. Strength values

expressed in terms of the stressed

cross-section.

Cold-profiled threaded bolts in ETG® 25

have a significantly higher fatigue

strength than those made of conven-

tional finally tempered material.

– mean stress σm 450 [N/mm2]

– M 12 thread σA ±80 [N/mm2]

– M 16 thread σA ±65 [N/mm2]

Comparison with rolled and quenched

and tempered thread in strength classes

8.8 to 12.9.

AS = ( )2ϖ

4

d2 + d3

2

14

ETG® 25 can be bent, machined

and refined

Bendability

Despite its high strength, ETG® 25 can

be bent without difficulty. No crack

initiation is evident on the tension side

in the technological bending test to

DIN 50111 when ETG® 25 is bent through

180 ° with a stamp.

Relaxation behaviour

A key property, especially for the

production of threaded parts, is the be-

haviour of the material in respect of

stress relaxation. The following diagram

shows the relaxation behaviour of

ETG® 25 in the form of the relative per-

centage stress reduction after 1000h

storage at temperatures of between RT

and 300 °C. The specimens used were

M 12 threaded bars pretensioned at

0,7 x Rp0,2.

Machinability

ETG® 25 is particularly suitable for ma-

chining and has the following advantages

compared with quenched and tempered

parts of a similar strength:

– improved chip break-off

– good surface finish after machining

– low internal stress

– low distortion

Surface finishing

Most surface finishes can be applied to

ETG® 25. For example, it can be hot-

galvanised, chromated, chromium-plated,

nickel-plated and alkaline-blackened, etc.

At treatment temperatures above 300 °C,

it should be noted that the proof stress

and tensile strength are reduced some-

what. Pickling to remove oxides can be

dispensed with. Providing galvanisation

is performed correctly, there is no dan-

ger of hydrogen embrittlement.

In the case of surface finishing, ground

material is recommended.

Stress relaxation of ETG® 25

40

30

20

10

0 RT 100 200 300

Test temperature [°C] Holding time 1000 hours

Str

ess

red

uct

ion

[%

]

15

Orientation values for various machining processes Machining guidelines Vc [m/min] and f [mm/E] ETG® 25Multi-spindle CNC turning Vc roughing 150 – 200(Carbide tooling, coated) f 0.08– 0.20 Vc finishing 140 – 180 f 0.08 – 0.20 Vc plunging/parting-off 80 – 160 f 0.05 – 0.20Multi-spindle CAM turning Vc roughing 80 – 140(Carbide tooling, coated) f 0.05 – 0.20 Vc finishing 80 – 120 f 0.05 – 0.20 Vc plunging/parting-off 50 – 130 f 0.05 – 0.20Short-bed turning CNC Vc roughing 150 – 200(Carbide tooling, coated) f 0.08 – 0.20 Vc finishing 150 – 200 f 0.08 – 0.20 Vc plunging/parting-off 80 – 160 f 0.05 – 0.20Plain turning CNC Vc roughing 120 – 160(Carbide tooling, coated) f 0.05 – 0.20 Vc finishing 120 – 160 f 0.05 – 0.30 Vc plunging/parting-off 30 – 90 f 0.05 – 0.20Drilling Vc 30 – 50(Carbide tooling, coated) f 0.05 – 0.25Drilling Vc 20 – 40(HSS, coated) f 0.05 – 0.25Reaming Vc 10 – 25(Carbide tooling, coated – HSS, coated) f 0.10 – 0.20External/internal threading (Chase threading, carbide/HSS, coated) Vc 50– 140Internal threading(Cutting, carbide tooling, coated) Vc 10 – 15Internal threading(Forming, carbide tooling, coated) Vc 80 – 160

Values as a function of the machine statics, cutting edge geometry, cooling lubricant, dimensions and drill diameter.

Despite its high strength,

ETG® is also readily weldable

Weldability

Despite its high strength, ETG® 25 is

particularly suited to welding. It must,

however, be borne in mind that, de-

pending on the welding conditions and

the weld metal, there may be a reduc-

tion in strength and an increase in

hardness in both the weld itself and the

heat-affected zone. The hardness in-

crease is only slight, on account of the

chemical composition of ETG® 25,

and it can be eliminated through tem-

pering at 400–450 °C.

Heat fusion welding

Care should be taken to ensure that

welding is performed with the lowest

possible level of heat application. The

strength reduction is determined not

only by the base material but also by the

weld metal employed. The best results

have been achieved with gas-shielded

welding. To take the example of MIG

welding:

– ETG® 25 Ø 9 mm

– weld metal Böhler

2,5 Ni-IG (ER 80, S-Ni 2)

– welding point milled into a wedge

shape (x-seam)

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The technical information contained in this document reflects current results obtained using gener-ally accepted testing procedures on production batches. They do not give a guarantee of the suit-ability for any particular application. Responsibility lies with the user.

© Steeltec AG, 03.10

Heat fusion welding

260

240

220

200

180

160

20 16 12 8 4 0 4 8 12 16 20

| Weld seam [mm]

Har

dne

ss H

V20

Pressure weldingButt welding and flash butt weldingExample: flash butt welding ETG® 25 Ø 18,25 mm

320

300

280

260

240

220

200

25 20 15 10 5 0 5 10 15 20 25

| Weld seam [mm]

Har

dne

ss H

V10

19

Friction weldingETG® 25 to ETG® 25 Ø 18,25 mm

320

300

280

260

240

220

200

25 20 15 10 5 0 5 10 15 20 25

| Weld seam [mm]

Har

dne

ss H

V10

/HV

1

Hardness HV10 Hardness HV1

Steeltec AGPostfach, CH-6021 EmmenbrückeTelephone +41 41 209 63 63, fax +41 41 209 52 94www.steeltec.ch

Group Companies

Steeltec AGSalen, Postfach, CH-9536 Schwarzenbach SGTelephone +41 71 929 94 94, fax +41 71 929 94 95

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Steeltec Fournitures Industrielles Clusiennes S.A.R.L.Boîte postale 81, F-74302 Cluses CedexTelephone +33 4 50 98 41 88, fax +33 4 50 96 25 99

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