Electric Welding Machine Buying Guide: How to Choose the Right One?

Have you ever thought about the following situations of the electric welding machine that has been used for so long:

The power of the welding machine is too low to weld such thick plates;

The machine is too big for ordinary welding;

The welding machine is too heavy and I should buy a lighter one.

Don’t wait until you have bought an electric welding machine to regret that you bought one that is not suitable for you.

Electric Welding Machine Buying Guide: How to Choose the Right One? 1

This article will teach you how to buy the right welding machine for you.

Previously, electric welding machines were expressed in kilowatts.

Now, the rated current of electric welding machine is used to indicate the size of electric welding machine.

1. How to choose the size of electric welding machine?

Take the electric welding machine with a load duration of 60% as an example.

First of all, it is necessary to know the welding current or the electrode size.

Select the size of the electric welding machine according to the size of the welding current.

For example, if the welding current is 100A, then 100 divided by 0.8 (the square root of 0.6 is 0.77, which is convenient to remember and calculate by 0.8) is equal to 125A.

When purchasing, we should look at the nameplate on the back of the welding machine, and select the welding machine with 60% load duration current greater than 125A.

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If we don’t know the welding current but only know how much welding rod to use, we will choose the rated current of the welding machine according to the current of the welding electrode.

For example, if the rated current range of Φ4.0 welding rod is 170A~210A, then 170 divided by 0.8 (the square root of 0.6 is 0.77, which is convenient to remember and calculate by 0.8) is equal to 212A.

When selecting, we should look at the nameplate on the back of the welding machine, and select the welding machine with 60% load duration current greater than 212A.

Select electrode diameter according to plate thickness

Workpiece thickness mm<44-12>12
Electrode diameter mmNot exceeding the thickness of the workpiece3.2-4.0>4

Select electric welding machine according to welding rod

Electrode diameterφ 2.5φ 3.2φ 4.0φ 5.0φ 6.0
Welding machine current160A200A300A400A500A

The electric welding machine is an inverter welding machine with a load duration of 60%.

Rated current range of welding rod

Diameterφ1.6φ2.0φ2.5φ3.2φ4.0φ5.0φ6.0
Current A25-4040-6550-80100-130160-210200-270260-300

2. Select your own welding machine according to the welding needs

AC argon arc welding and pulse gas shielded welding shall be used for aluminum welding;

DC argon arc welding and pulse gas shielded welding shall be used for welding stainless steel;

Electric Welding Machine Buying Guide: How to Choose the Right One? 3

Manual welding, ordinary gas shielded welding, pulse gas shielded welding and DC argon arc welding are selected for carbon steel welding.

Since electric welding machine products are compulsorily certified by the state, when purchasing electric welding machines, it is necessary to consider that the welding machines produced by regular manufacturers that have passed 3C certification should be preferred.

When purchasing, check whether the nameplate on the welding machine has the manufacturer’s name, production address, specification and model, welding current adjustment range, load duration, input voltage, current and other contents, and select the welding machine according to the work needs.

Because there are many fake and inferior products on the market, some electric welding machines falsely mark the rated current and load duration.

For example, the nominal rated current is 400A, and the actual measurement is only more than 200 amps.

If possible, use a DC clamp type ammeter to measure the actual maximum welding current when purchasing, so as to avoid that the selected electric welding machine cannot be used normally.

3. Main problems in selection of manual arc welding machine

At present, there are a variety of manual arc welding machines on the market, including old AC welding machines, silicon rectifier DC welding machines, inverter DC welding machines.

Electric Welding Machine Buying Guide: How to Choose the Right One? 4

The first type of welding machine has many varieties and specifications, many brands, and different quality.

Facing so many welding machines, how to choose an economical and practical product?

To select manual arc welding machine, you must understand the following simple common sense of electric welding machine:

Positive connection method: 

The positive pole of the workpiece welding machine is the positive connection method during welding, and the positive connection method is generally used for welding acid electrodes.

Reverse connection method: 

The negative pole of the workpiece welding machine is reverse connection method during welding, and the reverse connection method is generally used for alkaline electrode and stainless steel electrode.

Load persistence rate:

Generally speaking, the working time of the welding machine when it reaches the maximum welding current (rated current) takes 10 minutes as a cycle, working for 6 minutes and resting for 4 minutes.

The welding machine is just not protected and will not be damaged.

The load persistence rate is 60%.

The load persistence rate of civil electric welding machines in the market is mainly 35% and 60%.

Welders with less than 100% load duration cannot weld for a long time at rated current.

The conversion relationship between load duration and long time large welding current is as follows:

Load duration=maximum welding current for a long time 2/rated current 2

Take the welding machine with 400A load duration of 35% as an example: 0.35=maximum welding current for a long time 2/4002.

That is, the maximum welding current for a long time is 236.63A.

In other words, this 400A welder with 35% load duration can only work at 236.63A current to achieve 100% duration.

Relationship between electrode diameter and welding current:

Applicable current of electrode = electrode diameter * 40

For example, if the welding current required by 4.0 electrode=4.0 * 40, the 160A current is the optimal current value for welding 4.0 electrode.

But in actual work, there will be some changes due to material, workpiece size, pursuit of efficiency and other factors.

Relationship between carbon rod diameter and welding current of carbon arc air gouging:

Applicable current of carbon rod = carbon rod diameter * 50

4. How to select electric welding machine?

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The type of welding machine directly affects the service life and welding process.

The selected model is small, just like a small horse pulling a cart, which is laborious and easy to damage the welding machine.

It’s a waste to choose too much.

The key is that the price is also high.

Therefore, we users should not buy the most expensive, but only the right one.

Don’t be greedy for cheap prices.

What you buy must be a fake product with poor after-sales service.

Some manufacturers sell it for 88-168 yuan, but the maximum output current is only 100A or even less.

They also falsely advertise 3.2 long welding rod and so on.

5. Advantages and disadvantages of AC welding machine and inverter welding machine

Advantages of AC welding machine: cheap;

Disadvantages: large power consumption (commonly known as electric tiger), low no-load voltage (not easy to start arc), unstable current, arc breaking, welding rod sticking, bulky, and only ordinary welding rods can be welded.

Advantages of inverter DC welding machine: low power consumption, high no-load voltage (easy to arc), stable current, continuous arc, non stick welding rod, light and flexible, applicable to all types of welding rods;

Disadvantages: The price is expensive.

Select the welding machine model according to the welding rod used (take 4.2 welding rod as an example)

Welding current=4.2 * 40=168A Considering that the actual current may fluctuate by 20%,

168A*1.2=210A

Please do not think that a 250 welding machine is enough.

Due to the fierce competition in the market price, most manufacturers replace small ones with large ones and replace inferior ones with good ones.

Taking AC welding machine as an example, almost the buyer and seller of welding machine in the market have reached such a consensus:

250A welding machine is only suitable for welding 2.5 electrodes;

315A welding machine is only applicable to welding 3.2 electrodes;

400A welding machine is suitable for welding 4.2 electrodes;

Obviously, there is a big gap between this and the national standards.

This also shows that when fake goods flood the market.

Even the standards have been changed.

In fact, when we bought a 400A welding machine from the market, what we really bought may be a national standard 250A or even smaller welding machine.

This is why an AC welding machine of the same model is one-third lighter than that of a decade ago.

We may select welding machine as follows:

If we buy back a 400A welding machine, we will adjust the current to the maximum during the trial, weld 4.2 electrodes (too small electrodes affect the output), and use a clamp meter to measure the maximum output welding current.

If the current reaches 400A, it does not mean that we bought a 400A welding machine.

When the current reaches 400A, it also depends on the load holding rate.

If the load persistence rate is 30%, the welding machine we bought can only be regarded as a 250A welding machine.

The real 400A welding machine should have a maximum current of 400A and be able to work for a long time under 400A current.

This is why some welders of the same model on the market are several times more expensive.

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6. Power consumption and economic benefits of electric welding machine

As an energy-saving product vigorously promoted by the country, how much power can inverter welding machine save for us?

The actual measured input current of two-phase AC welding machine is between 33A and 35A based on the comparison of welding 3.2 electrode and 130A current;

The actual measured input current of three-phase DC welding machine is 6A.

The power consumption is calculated as follows:

Power consumption of AC welding machine:

P=LJI=380*33=13.3KW

Power consumption of inverter welding machine:

P=1.732 * UI=1.732 * 380 * 6=3.95KW

Then, based on 26 days a month, 8 hours a day, and 80% utilization rate:

(13.3-3.95)*8*0.8*26=1361.36(kwh)

Then the inverter DC welding machine for welding 3.2 electrodes can save 1361.36 degrees of electricity per month than the AC welding machine.

Similarly, compared with welding 4.2 electrode and current 175A, the result is that each inverter DC welding machine saves 2204.8 kilowatt hours per month.

7. Other precautions

When purchasing the welding machine, check whether the nameplate on the welding machine has the name of the manufacturer, production address, specification, welding current adjustment range, load duration, welding machine weight and other contents, and then select the applicable products according to the work needs.

As the electric welding machine is a product with national compulsory certification, you must ask whether the product has passed the 3C compulsory certification when you purchase it, and you can also check and confirm it online;

Priority should be given to dealers with guaranteed after-sales service, good reputation and reputation.

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