Welding

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WELDING OF SWEBOR STEELS
Welding is the most used joining method for Swebor steels. Welding is performed on Swebor steel on a daily basis. It is important to consider many things as welding is a method where the originally properties of hardened material are destroyed. Here follows recommendations and advices that will guide you to successful welding of our steels.

WELDING HYGIENE

A good welding hygiene is to be considered: Pollutions such as water, oil, dust, paint and rust shall at the most be removed.

INFLUENCE OF ALLOYING ELEMENTS

For being hardened steel Swebor steels has a relatively low alloying content with a good weldability as a result. Generally a higher alloying content require higher preheating and a higher heat input.

HYDROGEN CRACKING

Hydrogen cracking is a phenomena where hydrogen gas is formed in the material creating so high pressure in the “bubbles” that they “explode” and the material crack/fractures. Hydrogen cracking comes from:

1. Hydrogen in the weld/material

2. Stresses in the weld/material.

To avoid hydrogen cracking this must be considered:

1. Minimize the hydrogen content in the weld by:

Use the right pre heat temperature and heat input
Use welding consumables with low hydrogen content (make sure they also are dry)
Keep impurities such moist, snow, ice, water, oil, grease and paint out of the welding area.

2. Minimize the stresses in the weld joint:

Do not use welding consumables of a higher strength than necessary
Arrange the weld sequence so the residual stresses are minimized
Set the gap between the welded parts to a maximum of 3mm

PREHEAT TEMPERATURES FOR SWEBOR STEELS

The lowest preheat temperatures during welding is shown in the table below. These values are valid for unalloyed and low alloyed welding consumables. There are two general rules to consider during preheating:

1. The thickest plate determine the preheat temperature. See figure below.

2. When welding plates of different alloying content the highest alloyed/requiring the highest preheat value determine the preheat temperature.

MINIMUM RECOMMENDED PREHEAT TEMPEATURES FOR DIFFERENT SINGLE PLATE THICKNESS (mm)

preheating_temperatures

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HEAT INPUT

The amount of thermal energy that is added in weld affects the final properties of the joint. A general rule is that the less energy used the better final properties. But without sufficient amount of energy in the weld it will be unproductive and if to less energy is being used the weld will fail. To weld Swebor steels the Heat input shall be between 0,6 and 3 kJ/mm weld. To calculate the right heat input the formula below shall be used. As all welding environments and equipment are individually different the calculation must be verified by trials in your facility with your equipment.

Q = k x U x I x 60 / v x 1000 (For Swebor steels the value shall be between 0,6 and 3kJ/mm)

Q = Heat input [kJ/mm]
U = Voltage [V]
I = C urrent [A]
v = Welding speed [mm/min]
k = Thermal efficiency [dimensionless]

Thermal efficiency k [dimensionless]
MM A 0.8
MAG, all types 0.8
SAW 1.0
TIG0.6

WELDING CONSUMABLES / FILLER METALS

All Swebor steels are low alloyed martensitic steels. As the martensitic structure is transformed to ferritic during welding a ferritic low strength welding material shall be chosen. Low strength material also prevent cracking in the weld by low stresses. It is important that the filler material shall be clean and dry in order to prevent hydrogen cracking. The hydrogen content shall be maximum 5 ml hydrogen/100 g weld.

Welding Method AWS filler material classification EN filler material classification
MAG. solid wire AWS A5.18 ER70X-X EN ISO 14341-A- G 38xxxxxxx
AWS A5.28 ER80X-X EN ISO 14341-A- G 42xxxxxxx
MAG. metal cored wire AWS A5.18 E7XC-X EN ISO 17632-A- T 42xxxxxH5
AWS A5.28 E8XC-X EN ISO 17632-A- T 46xxxxxH5
MAG. flux cored wire AWS A5.29 E7XT-X EN ISO 17632 -A- T 42xxxxxH5
AWS A5.29 E8XT-X EN ISO 17632 -A- T 46xxxxxH5
MMA AWS A5.5 E70X EN ISO 2560-A- E 42xxxxxxH5
AWS A5.5 E80X EN ISO 2560-A- E 46xxxxxxH5
SAW AWS A5.23 F7X EN ISO 14171-A- S 42xxxx
AWS A5.23 F7X EN ISO 14171-A- S 46xxxx

Suitable welding material from ESAB:
MMA – OK48.00 or OK48.04
MAG – OK12.51

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