อาร์กอน 4.6, 4.8 และ 5.0 — เปรียบเทียบความบริสุทธิ์ของแก๊สปกคลุม
Purity grades, air separation and the question of which grade really pays off
AI generated 4.6, 4.8 และ 5.0 หมายถึงอะไร ทำไม 100 % จึงไม่มีจริง และความบริสุทธิ์ระดับไหนที่คุ้มค่าจริงสำหรับเหล็ก อะลูมิเนียม ไทเทเนียม และการวิเคราะห์สเปกตรัม
What 4.6, 4.8 and 5.0 actually mean
Argon is sold as in purity grades. The number counts the nines after the decimal point: 4.6 = 99.996%, 4.8 = 99.998% and 5.0 = 99.999% purity. The rest is foreign matter – mainly , and moisture.
How argon is produced – and why 100% does not exist
Argon comes from fractional cryogenic air separation, the Linde process: air is liquefied and split into its components in a distillation column. The problem: the boiling point of argon (−185.8 °C) sits extremely close to the oxygen boiling point (−182.96 °C). The two gases can only be separated with great effort – so traces of the other always remain. Thermodynamically, 100% purity does not exist.
What residual oxygen does
When stainless steel and , even a tiny amount of residual oxygen reacts with the hot pool. The result: – the colored edges next to the weld everyone knows. On titanium that is already enough to make the part brittle and unusable.
Which purity is really worth it?
• Structural steel, unalloyed steel and ordinary repair welds → 4.6 is the economical standard and fully sufficient for most TIG/MIG jobs.
• TIG welding of → 4.8 gives measurably cleaner, bright seams with fewer oxide inclusions ("pepper").
• , , and spectrometry → 5.0 is mandatory so that ppm-level oxygen and nitrogen traces cannot cause embrittlement.
The practical tip
Do not blindly buy the most expensive gas. Check what your material needs: standard → 4.6, aluminum TIG → 4.8, reactive metals and analytics → 5.0.