High pressure seamless tube is a kind of boiler tube, which has strict requirements on the steel used to manufacture steel tubes. High pressure seamless pipes are often used in 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. The steel pipe is required to have high lasting strength, high oxidation corrosion resistance, and good organizational 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 pipe is a high-quality carbon steel pipe used to manufacture various structures of low-pressure boiler superheated steam pipes, boiling water pipes and hot steam pipes for locomotive boilers, large smoke pipes, small smoke pipes and arch brick pipes.
Steel pipe hardness
1. Hardness requirements:
a) The alloy structural steel pipe and stainless (heat-resistant) steel pipe with outer diameter ≤127mm should be tested for hardness, and the hardness value should meet the requirements:
b) According to the requirements of the buyer, after negotiation between the supplier and the buyer, the high-quality carbon structural steel pipe and the alloy structural steel pipe with an outer diameter of >127m can be used for hardness requirements.
2. Hardness test:
a) For steel pipes with wall thickness ≥5.0mm, Brinell hardness test or Rockwell hardness test should be done:
b) For steel pipes with wall thickness <5.0mm but ≥1.7mm, Rockwell hardness test should be done:
c) For steel pipes with wall thickness <1.7mm, no hardness test is required:
d) When the purchaser stipulates in the contract that the steel pipe is subjected to the Vickers hardness test, the Vickers hardness test shall be done.
3. According to the requirements of the buyer, after negotiation between the supplier and the buyer, and the test temperature is indicated in the contract, the supplier can do the high temperature specified non-proportional elongation strength (Rp0.2) test of the steel pipe, and its value should meet the regulations.
Steel pipe length
1. Usual length
The usual length of the steel pipe is 4000mm~12000mm. After negotiation between the supplier and the buyer, short-length steel pipes with a length of not less than 3000mm can be delivered, but the quantity should not exceed 5% of the total delivery quantity of the batch of steel pipes.
2. Fixed length and double length
According to the requirements of the buyer and specified in the contract, the steel pipe can be delivered in fixed length or double length. The length of fixed length or the total length of multiple lengths of the steel pipe should be within the usual length, and the allowable deviation of the whole 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 allowance shall be reserved according to the following provisions:
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, it is 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 full-length curvature of the header pipe should be no more than 12mm.
High-pressure seamless pipe is a high-quality carbon steel pipe used to manufacture various structures of low-pressure boiler superheated steam pipes, boiling water pipes and hot steam pipes for locomotive boilers, large smoke pipes, small smoke pipes and arch brick pipes.
| Dimensions and allowable deviations of seamless steel pipes for high pressure boilers | |
|---|---|
| Deviation level | Standardized outer diameter tolerance |
| D1 | ±1.5%, min.±0.75mm |
| D2 | ±1.0%. Min±0.50mm |
| D3 | ±0.75%. Minimum ±0.30mm |
| D4 | ±0.50%. Min±0.10mm |
Steel pipe hardness
1. Hardness requirements:
a) The alloy structural steel pipe and stainless (heat-resistant) steel pipe with outer diameter ≤127mm should be tested for hardness, and the hardness value should meet the requirements:
b) According to the requirements of the buyer, after negotiation between the supplier and the buyer, the high-quality carbon structural steel pipe and the alloy structural steel pipe with an outer diameter of >127m can be used for hardness requirements.
2. Hardness test:
a) For steel pipes with wall thickness ≥5.0mm, Brinell hardness test or Rockwell hardness test should be done:
b) For steel pipes with wall thickness <5.0mm but ≥1.7mm, Rockwell hardness test should be done:
c) For steel pipes with wall thickness <1.7mm, no hardness test is required:
d) When the purchaser stipulates in the contract that the steel pipe is subjected to the Vickers hardness test, the Vickers hardness test shall be done.
3. According to the requirements of the buyer, after negotiation between the supplier and the buyer, and the test temperature is indicated in the contract, the supplier can do the high temperature specified non-proportional elongation strength (Rp0.2) test of the steel pipe, and its value should meet the regulations.
Steel pipe length
1. Usual length
The usual length of the steel pipe is 4000mm~12000mm. After negotiation between the supplier and the buyer, short-length steel pipes with a length of not less than 3000mm can be delivered, but the quantity should not exceed 5% of the total delivery quantity of the batch of steel pipes.
2. Fixed length and double length
According to the requirements of the buyer and specified in the contract, the steel pipe can be delivered in fixed length or double length. The length of fixed length or the total length of multiple lengths of the steel pipe should be within the usual length, and the allowable deviation of the whole 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 allowance shall be reserved according to the following provisions:
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, it is 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 full-length curvature of the header pipe should be no more than 12mm.
