Frequently Asked Questions

This information is for general use and is not intended to be specific answers for your exact questions.

My welding machine keeps shutting off after I've been welding for 5 to 10 minutes.
What is Duty Cycle?
What do the numbers on welding rod mean?
What do the terms TIG and MIG stand for?
What shielding gas should I use?
Cable size vs. cable length
What is the difference between brazing and welding?
What tip sizes do I use for oxy-acetylene welding and what pressures do I set on my regulators?
What size cutting tip do I use?

1. My welding machine keeps shutting off after I've been welding for 5 to 10 minutes.

You are probably experiencing the effects of Duty Cycle. Many machines are designed to shut down automatically after a period of continuous operation. This feature is there to protect the machine from over-heating. Consult owners manual for duty cycle rating for your machine model.

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2. What is Duty Cycle?

Duty cycle is the amount of time in a ten-minute period that a welding machine may be operated continuously without fear of overheating or damaging its components. Duty cycle is expressed as a percentage [%]. For example, a machine with a 60% duty cycle at 200 amps may be operated continuously for 6 minutes at that amperage [60% of 10 minutes]. The remaining four minutes of the cycle will be used to cool the machine down. Duty cycle percentages will change for a given machine depending on the output selected. It is possible to have several duty cycles listed. In general, the higher the output the, lower the percentage of duty cycle.

You should also note that many welders manufactured today are equipped with devices that will automatically shut the machine down if operating temperatures are exceeded. Letting the machine cool down will normally reset the system. Refer to operators manual for manufactures suggested "Duty Cycles".

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3. What do the numbers on a coated electrode welding rod mean?

Arc welding electrodes are coded by the American Welding Society [AWS]. Each AWS number gives complete information about the electrode.

Classifications of mild and low alloy steel electrodes are based on an 'E' prefix and a four or five digit number. The first two digits [or three, in a five digit number] indicate the minimum required tensile strength in thousands of pounds per square inch [psi]. The next to last digit indicates the welding position in which the electrode is capable of making satisfactory welds. [1 = All positions, 2 = Flat position and horizontal fillets]. The last digit indicates the type of current to be used and the type of covering on the electrode [see fig. 1].

fig. 1

FOURTH DIGIT	TYPE COATING	CURRENT
0	ORGANIC	DC+ only
1	ORGANIC	AC, DC+, DC-
2	RUTILE	AC or DC-
3	RUTILE	AC, DC-, DC+
4	RUTILE, IRON POWDER	AC, DC-, DC+
5	LOW HYDROGEN	DC+ only
6	LOW HYDROGEN	AC or DC+
7	MINERAL IRON POWDER	AC, DC-, DC+
8	LOW HYDROGEN, IRON POWDER	AC or DC+

Example: E6010

a.	The prefix [EXXXX] designates an arc welding electrode.
b.	The first two digits [E60XX] indicate a minimum tensile strength of 60,000 psi.
c.	The next digit [EXX1X] indicates position; All positions.
d.	The last digit [EXXX0] indicates an organic coating and DC+ current

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4. What do the terms TIG and MIG stand for?

The American Welding Society refers to these two processes as GTAW [gas tungsten arc welding] for TIG and GMAW [gas metal arc welding] for MIG. TIG [Tungsten Inert Gas] aka (GTAW) "Gas Tungten Arc Welding" and MIG [Metal Inert Gas] aka "Gas Metal Arc Welding" refer to two electric welding processes in common use today. They are very different and each has characteristics making them suitable for particular welding applications. In brief;

TIG (GTAW) welding uses a non-consumable electrode that provides the arc and a separate filler materialis added manually in the form of a rod. In addition, the TIG (GTAW) torch delivers a shielding gas to the weld site to minimize weld oxidation and/or alter the characteristics of the weld metal. In technique it is much like handling a oxy-acetylene welding torch though it is an electric process rather than flammable gas. It produces high quality welds and is especially suitable for aluminum and stainless steel metals.

MIG (GMAW) welding uses a device to automatically feed welding filler material into the weld site. The material is in the form of wire and the wire itself is the electrode. As it is with the TIG torch, the MIG (GMAW) torch delivers shielding gas to the weld site although welding wire is available that produces its own shielding gas in much the same way flux coated stick electrodes do.

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5. What shielding gas should I use?

The primary purpose of shielding gas is to displace the air in the weld zone and thus prevent contamination of the weld. No single shielding gas can be used with every welding process or every metal.

Argon [A], helium [He], and carbon dioxide [CO₂] are the principal shielding gases used. Oxygen [O₂] is used as an additive to stabilize the welding arc. Listed below are some of the more common gas and gas mixture applications.

BASE METAL	SPRAY TRANSFER	DIP TRANSFER	PULSED SPRAY
Stainless Steel	A + .5% O₂ A + 1% O₂ A + 2% O₂	90% HE + 7.5% A + 2.5% CO₂	A + .5% O₂ A + 1% O₂ A + 2% O₂
Carbon and Low Alloy Steel	A + 1% O₂ A + 2% O₂ A + 5% O₂ A + 5% CO₂ A + 8% CO₂	CO₂ A + 25% CO₂ A + 8% CO₂ A + 5% CO₂	A + 1% O₂ A + 2% O₂ A + 5% O₂ A + 5% CO₂ A + 8% CO₂
Aluminum and Magnesium	Argon Helium A + 25% HE A + 75% HE A + .15% O₂	N/A	Argon A + 25% HE A + 75% HE A + .15% O₂

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6. Cable size vs. cable length

POWER CABLE

Wire Size	Max Amp @ 100 ft.	Voltage Drop / 100 ft.
4	105	2.6
6	80	3.2
8	55	3.42
10	40	4.0
12	25	4.0
14	20	6.4

WELD CABLE

Amps

Duty Cycle

Cable Sizes Required per Lengths

0 - 50 ft.

100 ft.

150 ft.

200 ft.

250 ft.

100

150

180

200

1/0

200

225

250

100

40 & 30

4 or 5

1/0

250

300

100

1/0

2/0

325

350

400

500

600

650

100

2/0

1/0

2/0

3/0

2/0

3/0

2 -1/0

2-1/0

3/0

2-1/0

2/0

1/0

2/0

3/0

2/0

3/0

2 -1/0

2-1/0

3/0

2-1/0

2/0

3/0

2 -1/0

2-1/0

4/0

2-1/0

2/0

3/0

4/0

2-2/0

3/0

4/0

2-3/0

2/3/0

2-3/0

800

1000

100

3-1/0

2-3/0

2-4/0

3-1/0

2-3/0

2-4/0

3-1/0

2-3/0

2-4/0

2-3/0

2-4/0

4-2/0

1000

1200

1500

100

3-3/0

3-4/0

4-4/0

5-4/0

3-3/0

3-4/0

4-4/0

5-4/0

3-3/0

3-4/0

4-4/0

5-4/0

3-3/0

3-4/0

4-4/0

5-4/0

3-3/0

3-4/0

4-4/0

5-4/0

These findings are typical findings, and are not necessarily from MetroPlex Welding Supply.

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7. What is the difference between brazing and welding?

Brazing is a process wherein metal is joined together by heating the base metal to approximately 800°F and then using a non-ferrous filler metal having a melting point below that of the base metal. The filler metal melts and adheres to the base metal. The base metal does not melt and there is no fusion as in the welding processes.

Most commercial metals can be brazed. Although brazed joints have a relatively high tensile strength they do not possess the full strength properties of conventional welding techniques. One very useful characteristic of brazing is its ability to join dissimilar metals.

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8. What tip sizes do I use for oxy-acetylene welding and what pressures do I set on my regulators?

Tip sizes and gas regulator settings are dependent on the thickness of the material to be welded and the type torch being used.

Reproduced below are the tip charts for two of the most popular types of torches in use. Call your local Metroplex Welding Supply branch if you don't see your particular torch listed here.

Harris Welding Torches and Tips

Metal Thickness

Tip Size

Rod Size

Oxygen [PSIG]
E. P. U. P.

Acetylene [PSIG]
E. P. U. P.

3/64'

1/16'

3/32'

1/8'

3/16'

1/4 - 3/4'

1/16'

3/32'

1/8'

5/32'

3/16 - 3/4'

.25

[4 oz.]

or more

E. P. = Equal Pressure U. P. = Universal Pressure

VICTOR Welding Torches & Tips

Metal Thickness

Tip Size

Oxygen [PSIG]

Acetylene [PSIG]

Min.

Max.

Min.

Max.

Up to 1/32'

1/16 - 3/64'

1/32 - 5/64'

3/32 - 7/64'

1/16 - 1/8'

1/8 - 3/16'

3/16 - 1/4'

1/4 - 1/2'

1/2 - 3/4

3/4 - 1'

000

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9. What size cutting tip do I use?

The type of torch you are using and the thickness of material being cut determine the proper size cutting-tip for use in oxy-acetylene flame cutting.

Reproduced below are the tip charts for two of the most popular types of torches in use.

Harris Cutting Torches and Tips

Thickness of Metal in Inches

Tip Size

Oxygen Pressure [PSIG]

Light gauge to 3/16

3/16 - 3/8

3/8 - 5/8

5/8 - 1

1 - 2

2 - 3

3 - 6

000

15 - 30

20 - 30

30 - 40

35 - 50

40 - 55

45 - 60

50 - 75

For acetylene, use one piece tips with 5-6 PSIG acetylene pressure.

For MAPP, natural gas, or propane, use two piece tips with 4 oz/sq.in. or higher fuel gas pressure

Victor Cutting Torches - Tip Series 1-101, 3-101, 5-101

Metal Thickness

Tip Size

Cutting Oxygen [PSIG]

Preheat Oxygen [PSIG]

Acetylene [PSIG]

1/8'

1/4'

3/8'

1/2'

3/4'

000

20/25

25/30

30/35

35/35

35/40

40/45

40/50

45/55

3/5

3/6

4/7

4/8

5/10

6/12

3/5

3/6

4/8

5/11

6/16

- CAUTION - At no time should the withdrawal rate of an individual acetylene cylinder exceed one-seventh of the cylinder contents. If additional flow capacity is required, use an acetylene manifold of sufficient size to supply the necessary volume.

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