INTRODUCTION TO THE STRUCTURE OF SEAMLESS STEEL PIPE

Fluid seamless steel pipe seamless steel pipe structure and distinction: GB / T 8162-2008 “seamless steel structure,” This standard applies to general structure, mechanical structure with seamless steel tubes, GB / T 8163-2008 “transmission fluid with no pipe joints “standard applies generally seamless transmission fluid. The main difference is the structure of seamless steel pipe seamless steel pipe by root hydraulic fluid test or ultrasonic, eddy current, magnetic flux leakage inspection. Thus, the selection pressure on a standard line pipe, seamless steel structure should not be used.

Fluid seamless steel weight calculation formula: [(OD - Wall Thickness) * Thickness] * 0.02466 = kg / m (weight per meter)

Process

Sanitary Mirror Tube process:

Tube – test – peeling – test – heating – piercing – pickling – grinding – dry lubricant – welding head – cold drawn – solution treatment – Pickling – Pickling passivation – test – cold – to oil – the first cut – dried – in polish – outside polished – testing – identification – product packaging

Industrial process

Tube – test – peeling – test – heating – piercing – pickling – grinding – dry lubricant – welding head – cold drawn – solution treatment – Pickling – Pickling passivation – test

Pickling defects

Pickling hydrogen in addition to the iron oxide skin peeling effect, but also to 15CrMo alloy steel pipe within the matrix diffusion and aggregation of impurities or pores at, resulting in increased stress, reduce 15CrMo alloy steel pipe plastic increased 15CrMo alloy steel pipe brittle, which species effect called hydrogen embrittlement. Hydrogen embrittlement is mainly affected by the rate of diffusion of hydrogen atoms. The diffusion rate of hydrogen and the following factors:

1. In sulfuric acid solution of hydrogen diffusion rate higher than the rate of diffusion of the hydrochloric acid solution.

2. With the improvement of the pickling temperature, the hydrogen diffusion rate increased sharply, and increase the acid concentration, the diffusion rate of hydrogen was not much improvement. Therefore, it is best not hot pickling at low concentrations.

3. Pickling some inclusions such as arsenic (As), antimony (Sb), hydrogen sulfide (H2S) and sulfur dioxide (SO2) increase the rate of diffusion of hydrogen atoms, which increases the possibility of hydrogen embrittlement.

4.15CrMo chemical composition of steel pipe for the diffusion of hydrogen atoms also affected. Measures to prevent hydrogen embrittlement is operated in accordance with the provisions of acid concentration and temperature, to shorten the pickling time, time and the amount added corrosion inhibitors.

Still present on the surface of steel pipe 15CrMo owe pickling after pickling has not been a net addition of iron oxide, a phenomenon called under-pickling. Less pickling can be divided into all owe less pickling and pickling according to local causes. Causing all of the reasons is due to acid pickling time is short, low acid density or low temperature; causing local pickling is not due to reasons plus horn or 15CrMo alloy steel pipe surface oil and other yard material locally. Pickling pickling methods available to continue to be under-saving.

Pickling, when carbon steel pickling, rough surface and dark color; when chromium stainless steel pickling, the surface was gray and very rough, serious round hole a certain depth – pinholes. It causes acid pickling temperature is too high, or too long pickling acid concentration is too high. This deficiency can not be saved in the event of 15CrMo alloy steel pipe performance adversely affected. After pickling 15CrMo alloy steel tubes in the rolling process it is easy to stick or roll crusher.

After residues or rust pickling addition to iron salts remaining on the surface of 15CrMo alloy steel pipe, there is a layer of 15CrMo alloy steel pipe from the oxides or salts of other elements of the composition of the residue. These residues to clean up the billet surface defects detrimental, if not washed off the surface of the slab will continue to rust and yellow.

Representative material

Carbon steel, 20,45 steel; alloy steel Q345,20Cr, 40Cr, 20CrMo, 30-35CrMo, 42CrMo and so on.

The formula

Calculation Method for Structural seamless steel pipe: structural steel weight of = 0.25 × π × (outer diameter of the square – the square of the inner diameter) × L × steel proportion

Where: π = 3.14 L = length of pipe steel structure proportion taking 7.8

Therefore, the structure of seamless steel pipe weight = 0.25 × 3.14 × (outer diameter of the square – the square of the inner diameter) × L × 7.8 * If the size of the unit to take meter (M), the weight of the results of the calculation in kilograms (Kg).