ASTMA333GR.6 seamless steel pipe is an American standard seamless steel pipe for low-temperature pipelines. High-quality American standard seamless steel pipes for low-temperature resistant pipelines are steel pipe products used in special environments. The main requirement is that the finished steel pipe has good impact toughness in a low temperature environment (usually below -45°C).
ASTMA333GR.6 seamless steel pipe is an American standard seamless steel pipe for low-temperature pipelines. High-quality American standard seamless steel pipes for low-temperature resistant pipelines are steel pipe products used in special environments. The main requirement is that the finished steel pipe has good impact toughness in a low temperature environment (usually below -45°C). Ensure that no low-temperature brittle fracture occurs during use.
ASTMA333GR.6 seamless steel pipe spot specifications: 8-1240×1-200mm<1 xxs="">
Implementation standard: ASTM A333
Chemical composition of ASTMA333GR.6 seamless steel pipe:
Carbon: ≤0.3, Manganese: 0.2~1.06, Phosphorus: ≤0.025, Sulfur: ≤0.025, Silicon: ≥0.10, Nickel ≤ 0.40, Chromium: ≤0.30, Copper: ≤0.40, Vanadium: ≤0.08, Niobium: ≤0.02, Molybdenum: ≤0.12.
When the carbon content is lower than 0.30%, for every 0.01% decrease, the manganese content can be increased by 0.05% above 1.06% until the maximum allowed manganese content is 1.35%.
Based on the protocol, niobium content can be increased to 0.05% for melt analysis and 0.06% for finished product analysis.
Heat treatment requirements:
1. Normalizing above 815°C.
2. Normalize above 815°C, then temper.
3. Thermoforming between 845-945°C, then furnace cooling above 845°C (only applicable to seamless tubes).
4. Press 3 for processing and tempering.
5. Tempering after quenching above 815°C.
Mechanical performance requirements:
Yield strength: ≥240Mpa
Tensile strength: ≥415Mpa
A333GR.6 cryogenic tube process flow:
Tube blank - inspection - peeling - inspection - heating - perforation - pickling - grinding - lubrication and air drying - welding head - cold drawing - solution treatment - pickling - pickling Passivation - inspection - cold rolling - degreasing - cutting - air drying - internal polishing - external polishing - inspection - marking - finished product packaging.
(1) C element
C element can form solid solution in steel to form interstitial solid solution. During the heat treatment process, the diffusion or segregation of carbon atoms has an important impact on the formation and distribution of carbides and the properties of steel. Carbide is a hard phase that can improve the strength, hardness and wear resistance of steel, but is not conducive to improving the toughness of steel, so the carbon content needs to be reduced as much as possible;
(2) Si, Mn elements
Si is used to remove oxygen from steel during the steel smelting process. Si helps to improve the high-temperature deoxidation and acid corrosion resistance of steel; Mn is a strengthening element that can improve the hardness and wear resistance of steel and reverse the austenite transformation. Stable, but Mn easily forms MnS inclusions with S, which will have a bad impact on the properties of steel;
(3) S, P elements
From the perspective of the effects of elements on low-temperature toughness, C, Si, P, S, N, etc. are generally considered to be harmful elements, with P causing the greatest harm, while Mn, Ni, etc. are beneficial elements. Therefore, ASTM A 333/A333M-2013 mainly relies on Mn to improve the low-temperature performance of Gr6 and strictly controls the S and P content.
(4) Ni element
Ni is an alloy element that promotes the stable existence of austenite, which is beneficial to the improvement of steel plasticity and strength, and at the same time reduces the brittle-hard transition temperature of steel. Nickel-rich reversed austenite can be stored stably under extremely low temperature conditions, which is beneficial to the low-temperature toughness of A333Gr6. Kaizen has an important impact. The 2016 and later versions of A333GR.6 further enhance their low-temperature performance with the help of newly added Ni, V, Nb and other alloying effects.
