What will affect the performance of seamless black steel pipe?

What will affect the performance of seamless black steel pipe?

Chemical composition of steel: The chemical composition of steel is one of the most important factors affecting the performance of seamless black steel pipes. It is also the main basis for formulating the rolling and heat treatment process parameters of seamless black steel pipes.

1) Alloying elements: intentionally added according to purpose

2) Residual elements: brought into steelmaking and properly controlled

3) Harmful elements: strictly controlled (As, Sn, Sb, Bi, Pb), gases (N, H, O)

Out-of-furnace refining or electroslag remelting: improve the uniformity of chemical composition in steel and purity of steel, reduce non-metallic inclusions in tube blanks and improve their distribution.

Seamless black steel pipe geometric precision and shape

1) The accuracy of the outer diameter of seamless black steel pipe: depends on the method of determining (reducing) the diameter, the operation of the equipment, the process system, etc.

Outer diameter tolerance δ=(D-Di)/Di×100%
D: Maximum or minimum outer diameter mm
Di: nominal outer diameter mm

2) The wall thickness accuracy of seamless black steel pipes: It is related to the heating quality of the tube blank, the process design parameters and adjustment parameters of each deformation process, the quality of the tools and their lubrication quality, etc.

Wall thickness tolerance: ρ=(S-Si)/Si×100%
S: Maximum or minimum wall thickness of cross section
Si: Nominal wall thickness mm

3) Ovality of seamless black steel pipe: Indicates the degree of out-of-roundness of seamless black steel pipe.

4) Length of seamless black steel pipe: normal length, fixed (multiple) length, length tolerance

5) Curvature of seamless black steel pipe: Indicates the curvature of seamless black steel pipe: curvature per meter of steel pipe length, curvature of the entire length of seamless black steel pipe

6) The inclination of the end face of the seamless black steel pipe: indicates the inclination of the end face of the seamless black steel pipe and the cross section of the seamless black steel pipe.

7) Seamless black steel pipe end bevel angle and blunt edge

Seamless black steel pipe surface quality: surface finish requirements

1) Dangerous defects: cracks, inward folding, outward folding, curling, delamination, scarring, concave pulls, convex bulges, etc.

2) General defects: pits, blue lines, scratches, bumps, slight internal and external straight lines, rolling marks, etc.

Reason

1) Caused by surface defects or internal defects of the tube blank.

2) Caused during the production process, such as incorrect design of rolling process parameters, uneven mold surface, poor lubrication conditions, unreasonable pass design and adjustment, etc.

3) During the heating, rolling, heat treatment, and straightening processes of steel billets (steel pipes), if the heating temperature is improperly controlled, causing uneven deformation, unreasonable heating and cooling rates, or excessive straightening deformation, resulting in excessive residual stress, then It may also cause surface cracks in seamless black steel pipes.

Steel management properties: normal temperature mechanical properties, high temperature mechanical properties, low temperature properties, corrosion resistance. The physical and chemical properties of seamless black steel pipes mainly depend on the chemical composition of the steel, the structure of the steel, the purity of the steel and the heat treatment method of the seamless black steel pipes.

Seamless black steel pipe process performance: flattening, flaring, curling, bending, welding, etc.

Seamless black steel pipe metallographic structure: low magnification (macro), high magnification (micro) M, B, P, F, A, S

Coating of black steel seamless pipe

Black steel seamless pipe is uncoated steel, also known as black steel. The primary use is to deliver propane or natural gas to residential and commercial buildings. The pipe has no seams, making it a better pipe for transporting gas. Black steel seamless pipe is also used in fire sprinkler systems because it is more fire-resistant than galvanized pipe.

Key factors affecting black steel seamless pipe coating

1) The passivation film of black steel seamless pipes is a metastable structure that is thermodynamically suppressed, and its maintenance effect is related to the medium in the environment. Once it enters the geographical environment, it will cause chemical changes, so before painting, it is necessary to remove harmful substances attached to the surface of black steel seamless pipes;

2) The chemical potassium thiocyanate will seriously affect the coating of black steel seamless pipes. Therefore, the composition of potassium thiocyanate should be strictly controlled throughout the passivation process. Once the standard is exceeded, the black steel seamless pipe will be destroyed. Steel tube structure. Under normal circumstances, pharmaceutical companies will limit the dosage of potassium thiocyanate and perform the next actual operation according to the relevant preparation to ensure the coating of black steel seamless pipes;

3) The moisture content in black steel seamless pipes is low and the passivation properties are low, which will have a certain impact on the entire coating process. In order to better achieve the actual effect of a stronger coating, its essential influencing factors need to be improved;

4) As we all know, the surface of black steel seamless pipe is relatively smooth, because the smoother the surface, the less likely it is to be stained. During the production process, black steel seamless pipes will be polished and coated; in the actual production process, the corrosion resistance of black steel seamless pipes should be improved.