When it comes to steel pipes, understanding the factors that influence their actual weight is crucial for manufacturers, engineers, and purchasers alike. Several key elements can affect the weight of steel pipes, and being aware of these can lead to more accurate estimations and potentially cost-saving decisions. 

1. Material Differences

The type of material used in manufacturing steel pipes plays a significant role in determining their weight. For instance, stainless steel has a slightly higher density, ranging from 7.93 to 8.0 grams per cubic centimeter. As a result, steel pipes made from stainless steel may experience a weight increase of approximately 1% to 2% compared to other materials of the same specification. Additionally, alloy steels, due to variations in their composition, require adjustments based on their actual densities to calculate the precise weight. 

2. Manufacturing Tolerances

Manufacturing tolerances significantly impact the actual weight of steel pipes. The permissible wall thickness deviation is typically ±10%. This means that the actual wall thickness can range between 7.2 millimeters and 8.8 millimeters, which corresponds to a weight range between 110.6 to 135.0 kilograms per meter. While the influence of external diameter deviation on weight is relatively minor, factors such as ovality must also be considered. 

3. Surface Treatment and Coatings

The finish and surface treatment of steel pipes can also add to their overall weight. For example, anti-corrosion coatings, such as the three-layer polyethylene (3PE) system, can increase the weight by an additional 1 to 3 kilograms per square meter. A 630 steel pipe, with an estimated coating surface area of approximately 2 square meters per meter, could see an overall weight increase of about 2 to 6 kilograms due to surface treatment. Therefore, when estimating the weight of steel pipes, it is vital to consider any surface treatments or coatings applied.

In summary, the actual weight of steel pipes is influenced by several critical factors: material differences, manufacturing tolerances, and surface treatment or coatings. By understanding these aspects, stakeholders in the steel pipe industry can make more informed decisions that ensure better quality control, accurate pricing, and overall efficiency.