Preheating and Post-weld Heat Treatment

 

Preheating Treatment: For thick plates or when welding NV A steel plates in a low-temperature environment, preheating may be required. The preheating temperature is generally between 100 - 150℃. Thick plates dissipate heat quickly, and the cooling rate during welding is also fast, so it is easy to produce hardened structures and cracks. A low-temperature environment will accelerate the cooling rate of the weld and the heat-affected zone, increasing the risk of welding defects. Preheating can reduce the cooling rate of the welded joint, reduce the possibility of the formation of hardened structures in the heat-affected zone, thereby improving weldability and preventing the occurrence of welding cracks. Infrared heating equipment or flame heating can be used for preheating, and it is necessary to ensure that the preheating temperature is evenly distributed throughout the welding area of the steel plate.

 

Post-weld Heat Treatment: When the welded structure bears a large stress or when high toughness of the welded joint is required, post-weld heat treatment is needed. For example, in the key structural parts of ships or in welded structures subjected to alternating loads, post-weld heat treatment can eliminate the welding residual stress and improve the structure and performance of the welded joint. For example, tempering treatment can improve the hard and brittle structures in the heat-affected zone of welding and improve the toughness of the joint. Generally, the tempering temperature is between 550 - 650℃, and the holding time is determined according to factors such as the thickness of the steel plate. Usually, for every 25mm of thickness, the holding time is 1 - 2 hours. The heating rate and cooling rate also need to be reasonably controlled to avoid the generation of new thermal stresses.

 

 

 

 

 

 

 

 

NV A general Strength Chemical Composition
Grade	The Element Max (%)
	C	Si	Mn	P	S	Al	N
NV A	0.21	0.05	2.5 x C	0.035	0.035	-
	Nb	V	Ti	Cu	Cr	Ni	Mo

 

 

Ensuring the Cleanliness and Good Assembly Quality of the Welding Joint

 

Assembly Quality Control: Good assembly quality is an important factor in improving weldability. The gap of the welding joint should meet the requirements of the welding process. If the gap is too large, it may lead to excessive filling of the weld and the occurrence of welding defects. If the gap is too small, it may cause problems such as lack of fusion. At the same time, it is necessary to ensure the alignment accuracy of the welded parts to prevent stress concentration during the welding process, which may affect the welding quality and weldability.

 

 

 

Why Choose Us?
We take pride in our ability to provide custom solutions for our customers' unique needs.
We analyze and compare the previous products and the current technical situation of our NV A Steel Plate, and develop new technical specifications and processes.
Our customers trust us to deliver high-quality Cold-rolled Steel products on time and on budget.
We strictly implement the warm and thoughtful after-sales service, adhere to the development of good professional ethics.
We offer a wide range of Cold-rolled Steel products to meet diverse customer needs.
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Our factory is committed to upholding the highest standards of safety and quality.
All staff of our company and all departments work together to combine business management, professional technology, quantitative statistical methods and ideological education.
Our Cold-rolled Steel products are known for their durability and reliability.
Relying on the superior conditions and strong advantages of mass production, we are able to meet the different needs of our customers.

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