BULETINUL INSTITUTULUI POLITEHNIC DIN IAŞI Publicat de

Universitatea Tehnică “Gh. Asachi”, Iaşi Tomul LI (LV), Fasc. 5, 2005

Secţia CONSTRUCŢII DE MAŞINI

RESEARCHES REGARDING THE WELDING VALUES OPTIMIZATION OF TWO DIFFERENT MATERIALS

BY

GHEORGHE LUNGU, IONEL SÂRBU and OCTAVIAN FRÎNCU

Abstract. The work presents the manual welding technology of the 20Mn12V and the OL52-3k steel types. It contains a study about the basis metal and the presentation of the weld metal and, also, some tests done on the 20Mn12 steel. The welding technological values are described for two experimenting stages. The first stage welding process needs stress-relief thermal treatment after the welding, whereas the second stage one doesn’t need it. The described welding is for V joints splices. The work ends by presenting the welding technological instructions for butt-jointed cylinders of 10-20mm breadth of the 20Mn12V and OL52-3k steel. The basis metal used to manufacture the cylinders is the 20Mn12V and OL52-3K steel. Key words: welding technology, values optimization, different materials.

1. Introduction

The work presents the manual welding technology of the 20Mn12V and the OL52-3k steel types. It contains a study about the basis metal and the presentation of the weld metal and, also, some tests done on the 20Mn12 steel, which is off-gauge and absent form any norm, the data on this material being given in the quality certificates done in the laboratory.

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The welding technological values are described for two experimenting stages. The first stage welding process needs stress-relief thermal treatment after the welding, whereas the second stage one doesn’t need it.

The described welding is for V joints splices. The work ends by presenting the welding technological instructions for butt-jointed cylinders of 10-20mm breadth of the 20Mn12V and OL52-3k steel.

The basis metal used to manufacture the cylinders is the 20Mn12V and OL52-3K steel.

Table 1 The Chemical Composition of the OL 52-3k and 20Mn12V

Chemical Composition No. Steel

Steel Types. C Nn Si P S V Ni Cu Gr Ti

1. 20Mn12V 0,21 1,14 0,24 0,016 0,011 0,12 0,14 0,14 0,01 0,003 2. OL52-3k 0,22 1,6 - 0,05 0,05 - - - - -

Table 2

The Mechanic Characteristics of the OL 52-3k and 20Mn12V The Mechanic Characteristics KV [J] No.

Steel Steel

Types. Rp 0,2 [N/mm2]

Rm[N/mm2]

A5[%]

Z [%]

+200C 0 -200C

1. 20Mn12V 701 828 24.4 - - - - 2. OL52-3k 440 611 16.4 - - - -

The E.51.5.B110.2.O.H super base welding electrode was used as a weld

material. This electrode is often used for metallic constructions and is designed for highly stressed statically and dynamically structures, of low alloyed steel for up to –300C exploitation. When choosing the welding electrode, we took into account the mechanic rules and information about the chemical composition of the deposited metal

THE WELDED JOINT – DESIGN VALUES

Fig. 1 - Pipe-to-Pipe Joining Type

de maşini Bul. Inst. Polit. Iaşi, t. LI (LV), Fasc. 5, 2005 337

Fig. 2 - Pipe-to-Cover Joining Type

THE WELDING TECHNOLOGICAL VALUES The preheating test: We used six calculation methods for the preheating test: The IIS Method The equivalent carbon is calculated using the following relation:

(1) 415520SiNiVMoCrMnCCe ++

++++=

For the OL52-3k steel: %35,0=eC and for the 20Mn12V steel: 413,0=eCThe welding type Ls in chosen from the method chart according to the Ce

function and the hards type. For OL52-3k it’s Ls=C and for 20Mn12V Ls=F. The TCN thermal severity numbers are calculated according to the δ, the

welding tests thickness and the nc cooling ways number. The preheating temperature depending on Ls, TCS and the electrode diameter result from the method chart. For OL52-3k Tpr=250C and for 20Mn12V Tpr= 1750C

The Séférian Method: The same Ce is calculated from the basis metal chemical analysis as in the

IIS method. By using it, a Ce equivalent carbon is determined, taking into account the thickness of the welded pieces. ( 2 ) ( )δ005,01/ += ee CC

For OL52-3k: and 20Mn12V : 38,0/ =eC 52,0/ =eC

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For the OL52-3k steel: and for 20Mn12V:

Cpr0

1. 126=Θ

Cpr0

1. 182=Θ The Mrosko Method: The equivalent carbon is determined by using the following relation:

(3) 54156

CrNiMoCCe ++++=

For OL52-3k: and 20Mn12V: 50,0=eC 55,0=eC The following preheating values result from the method charts: For the OL52-3k steel: and 20Mn12V: Cpr

01. 75=Θ Cpr

01. 150=Θ

The B.S. Kosetkin Method:

(4) 144510246VCrNiSiMnCCe ++++++=

For the OL52-3k steel we obtain: 57,0=eC . For flow limit with resulting from the

chart.

2/736 mmN=σ Cpr0

1. 160=Θ

The K.I. Lebedeva Method: The equivalent carbon is determined by using the following relation:

(5) 541227566VMoNiPCuSiCrMnCCe ++++++++=

For the OL52-3k steel: 56,0=eC and for the 20Mn12V steel we obtain: . The following preheating temperature result from the method charts: 63,0=eC

For the OL52-3k steel: Cpr0

1. 260160 ÷=Θ

For the 20Mn12V steel: Cpr0

2. 310190÷=Θ The Tachenke and Killing Method: The equivalent carbon is calculated by using the relation:

(6) 41556

MoNiCrMnCCe ++++=

For the OL52-3k steel: 50,0=eC and for the 20Mn12V steel we obtain: . 55,0=eC

For these equivalent carbon values, the authors take into consideration a preheating temperature of . Cpr

02. 200100 ÷=Θ

de maşini Bul. Inst. Polit. Iaşi, t. LI (LV), Fasc. 5, 2005 339

The Estimated Preheating Temperature Determination: For the first stage of the tests, a temperature of 175-2000C, roughly chosen,

considering the preheating temperatures got from the described calculation methods. A temperature of 200-2200C was used in the second stage in order to slow down the cooling speed.

2. The Welding Electrical Values

A linear energy of 13– 20KJ/cm, experimentally determined will be used in

order to do the welded joining. We tested two welding methods, during two experimenting stages, with V joints for 18mm thickness.

2.1. First Stage Tests

The welding is made with super base electrodes of ϕ 3,25 and ϕ 4 mm. The electrodes are calcinated at 250-3000C for 2 hours, before using them. The root layer is made with ϕ 3,25 electrodes and the rest with ϕ4mm ones.

The welding is made horizontally, by rotating the cylinder. Different technological methods were tested. These were:

The welding without preheating and stress-relief The welding with preheating and stress-relief The welding with preheating and stress-relief (one test for 1 hour and one

test for 2 hours).

2.2. Second Stage Tests The welding is made using super base ϕ4mm electrodes for the root and

ϕ5mm for the other filling layers. The electrodes are calcinated at 250-3000C for 2 hours, before welding. The welding current for the ϕ4mm electrodes is of 170-180A, and for ϕ5mm of 230-240A. The welding voltage is of 23-27V.

The welding speed for ϕ4mm electrodes is 7,5-7,9m/h and for ϕ5mm ones is 7,6-7,8m/h, an experimentally determined speed. The linear energy of 13-20kJ/cm, experimentally determined.

3. Technological Accounts

When welding the last line, attention must be paid in order to weld it on the

OL52-3k steel and, thus, the last line will be welded on the 20Mn12V steel. The technological welding lay out: ─ the joints measuring check for the welding; ─ the joints adjustment for the welding; ─ the joints preheating for the temporary fixing; ─ the temporary pipe welding to the cylinder cover; ─ the temporary fixing cleaning for the welding;

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─ the welded temporary fixing checking; ─ the root layer welding with _4mm electrodes; ─ the after welding adjustment; ─ the visual final welded areas checking with penetrating liquids; ─ the mechanical processing of the increased height – if the test method

considers it necessary; ─ the visual checking with penetrating liquids – if there are any doubts.

4. Conclusions

The first stage of the welding process has used ϕ3, 25 mm superbase

electrodes for the root layer and ϕ4 mm for the filling layer. The welding linear energy was 13.000-18.000J/cm. One the thermal stress-relief treatment was done, all the mechanical tests results were appropriate. The second stage used ϕ4 mm superbase electrodes for the root layer and ϕ5 mm for the filling layers.

The welding linear energy was of 27.000-30.000J/cm. The conclusion is that this method doesn’t need thermal stress-relief treatment and is the optimal choice.

Technical University “Gh. Asachi”, Jassy Department of Machine Tools

Received September 2005

R E F E R E N C E S

1. G e r k e n J. M., K o t e c k i D. J. Stainless Steels. Publication No.M250, The Lincoln

Electric Company, 1990. 2. K o t e c k i D. J. Welding Parameter Effects on Open-arc stainless weld Metal Ferrite,

Weld J., 57, 4 (1978). 3. M c C o w a n C. N., S i e w e r t T. A., O l s o n D. L. Stainless Steel Weld Metal Ferrite

Content. Welding Research Council Bulletin 342, WRC, 1989.

CERCETĂRI PRIVIND OPTIMIZAREA PARAMETRILOR DE SUDARE A DOUĂ MATERIALE DIFERITE

(Rezumat)

Lucrarea prezintă tehnologia de sudare manuală a oţelurilor 20Mn12V cu oţelul OL52-3k. Lucrarea conţine un studiu asupra metalului de bază şi prezentarea metalului de adaos, conţine încercări efectuate pe oţelul 20Mn12V. Parametrii tehnologici de sudare sunt prezentaţi pentru două faze de experimentări. Tehnologia de sudare prezentată în prima fază necesită tratament termic de detensionare după sudare, iar tehnologia de sudare din faza a II-a nu necesită tratament termic post sudare. Sudarea este prezentată pentru tipuri de îmbinări cap la cap cu rostul în V. Lucrarea se încheie cu instrucţiuni tehnologice de sudare pentru cilindrii cap la cap de grosimi cuprinse între 10-20mm a oţelului 20Mn12V cu oţelul OL52 -3k.