Hardness requirements for high pressure seamless pipes

High-pressure seamless pipe is a kind of boiler pipe, which has strict requirements on the steel used in the manufacture of steel pipes. High-pressure seamless pipes are often used under high-temperature and high-pressure conditions, and the pipes will be oxidized and corroded under the action of high-temperature flue gas and water vapor. Steel pipes are required to have high durable strength, high resistance to oxidation and corrosion, and good structural stability. High-pressure boiler tubes are mainly used to manufacture superheater tubes, reheater tubes, gas guide tubes, main steam tubes, etc. of high-pressure and ultra-high pressure boilers.

High-pressure seamless pipes are high-quality carbon steel pipes for manufacturing low-pressure boiler superheated steam pipes, boiling water pipes and hot steam pipes, large smoke pipes, small smoke pipes and arch brick pipes for locomotive boilers of various structures.
 

1. Hardness requirements:
a) Alloy structural steel pipes and stainless (heat-resistant) steel pipes with an outer diameter of ≤127mm should be subjected to a hardness test, and the hardness value should meet the requirements:
b) According to the requirements of the buyer and after negotiation between the supplier and the buyer, high-quality carbon structural steel pipes and alloy structural steel pipes with an outer diameter of >127m can be used for hardness requirements.

2. Hardness test:
a) Steel pipes with a wall thickness ≥ 5.0mm should be subjected to Brinell hardness test or Rockwell hardness test:
b) Steel pipes with wall thickness <5.0mm but ≥1.7mm should be subjected to Rockwell hardness test:
c) For steel pipes with wall thickness <1.7mm, no hardness test shall be performed:
d) The Vickers hardness test shall be carried out when the purchaser stipulates in the contract that the steel pipe shall be subjected to the Vickers hardness test.

3. According to the requirements of the buyer, after negotiation between the supplier and the buyer, and specifying the test temperature in the contract, the supplier can carry out the high temperature specified non-proportional elongation strength (Rp0.2) test on the product. Steel pipe, its value should meet the regulations.

steel pipe length

1. Regular length
The usual length of the steel pipe is 4000mm~12000mm. After negotiation between the supplier and the buyer, short-tube steel pipes with a length of not less than 3000mm can be delivered, but the quantity shall not exceed 5% of the total delivery of the batch of steel pipes.

2. Fixed length and double length
According to the requirements of the purchaser and the provisions of the contract, steel pipes can be delivered in fixed lengths or double lengths. The fixed length of the steel pipe or the total length of the multi-section steel pipe should be within the normal length, and the allowable deviation of the total length should meet the following requirements:
a) Length≤6000mm, 0~10mm;
b) Length > 6 000 mm, 0~15 mm.
For each length of the ruler, an incision margin shall be reserved according to the following regulations:
a) Outer diameter ≤159mm, 5mm~10mm;
b) Outer diameter>159mm, 10mm~15mm.

curvature

The bending degree of each meter of steel pipe shall meet the following requirements:
a) When the wall thickness is less than or equal to 15mm, less than or equal to 1.5mm/m;
b) When the wall thickness is >15mm～30mm, ≤2.0mm/m;
c) When the wall thickness is >30mm, ≤3.0mm/m.
The curvature of the total length of the main pipe is not greater than 12mm.

Read more ：seamless carbon steel pipe

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