Steel structure refers to the steel structure, is one of the main types of building structure. The structure is mainly composed of steel beams, steel columns and steel trusses made of section steel and steel plates. Parts or parts are usually joined by welds, bolts, or rivets. Because of its light weight and simple construction, it is widely used in large factories, stadiums, high-rise buildings and other fields.

In the process of welding steel structure, there are many places to pay attention to. If you ignore it, you could make a big mistake.

Materials and main equipment for welding steel structure

Welding rod: selection according to design requirements, quality certificate must be provided. Bake as required before welding. Peeling of coating and core rust are strictly prohibited. If there is no design requirement, E43 series carbon steel electrode should be used for welding Q235 steel; E50 series low alloy structural steel electrode should be used when welding 16Mn steel; Low hydrogen electrode (alkaline electrode) should be used for welding important structures. Bake according to the instructions, place in an insulated bucket and take as needed. Acidic and alkaline terminals are not allowed to be mixed.

Arc guide plate: Arc guide plate is required when connecting with groove. The material and groove pattern of the arc plate should be the same as that of the weldment.

Main equipment: welding machine (AC, DC), welding wire, welding pliers, face mask, hammer, welding oven, welding insulation tube, wire brush, asbestos rod, thermometer and so on.

Operating conditions for welding steel structures

Familiar with drawings, welding process technical description.

The validity period of the welder certificate should be checked before welding of the steel structure to prove that the welder can undertake the welding work.

The onsite power supply must meet the welding power supply requirements.

Ambient temperature below 0℃, preheating and post-heating temperature should be determined according to the process test.

The operation procedure of welding steel structure

Welding process of steel structure:

Operation preparation → arc welding (flat welding, vertical welding, horizontal welding, reverse welding) → weld inspection.

Arc welding of steel structure:

Flat welding

Select qualified welding process, electrode diameter, welding current, welding speed, welding arc length and so on, and pass welding process test to verify.

Clean the weld: before welding, check whether the groove and assembly gap meet the requirements, whether the positioning welding is firm, there should be no oil and rust around the weld.

The baking electricity shall conform to the specified temperature and time. The electrical end removed from the oven should be put into the electrical end insulation bucket, as required to remove.

Welding current of steel structure: According to the thickness of the weldment, welding level, electrode type, diameter, welder proficiency and other factors, choose the appropriate welding current.

Welding arc initiation of steel structure: the arc point of fillet weld should be at the end of the weld, should be greater than 10mm, can not arbitrarily arc. After ignition and arc initiation, the electrode should be pulled away from the welding area immediately, so that the electrode and the component are kept in a gap of 2 ~ 4mm to produce an arc. Butt welds are combined with fillet welds. Both ends of the weld are provided with an arc guide plate and an outlet plate. The arc should be ignited on the arc guide plate and then welded to the welding area. The intermediate joint should be in front of the weld. Start the arc at 15-20mm. After the weldment is preheated, place the electrode back to the beginning of the weld, fill the molten pool to the desired thickness, and weld forward.

Welding speed of steel structure: constant speed welding is required to ensure uniform thickness and width of weld. It is recommended to keep the molten iron and molten slag in the molten pool at an equal distance (2 ~ 3mm) from the cover.

Welding arc length of steel structure: according to the different types of welding rod. The arc length is generally required to be stable. Acid electricity is generally 3~4mm, alkaline electricity is generally 2~3mm.

Welding Angle of steel structure: According to the thickness of two welds, welding Angle has two aspects. One is that the Angle between the electrode and the welding direction is 60 ~ 75°; The other is the Angle between the electrode and the weld. When the thickness is equal, the Angle between the electrode and the weldment is 45°; When the thickness of the weldment is different, the Angle between the electrode and the thicker part should be greater than the Angle between the electrode and the thinner part.