FAQ

What is the main difference between Q：304 and 316 stainless steel?

304 contains 18% chromium and 8% nickel, which is suitable for general environments such as food equipment; Adding 2% molybdenum to 316 can improve the chloride ion corrosion resistance by 50%, which is specially used in marine/chemical environment.

Does stainless steel rust represent unqualified quality?

Not necessarily. Surface floating rust may be caused by carbon steel dust pollution (it can be cleaned with 10% nitric acid), but if the matrix appears red rust, it is a corrosion problem, and the applicability of the material needs to be confirmed.

How to deal with the black edge of stainless steel after cutting?

This is a high-temperature oxidation phenomenon. It is suggested that: ① laser cutting is used to reduce the thermal impact; ② stainless steel pickling passivation paste is used immediately after cutting.

Why do medical stainless steels have to use 316L?

316l ultra-low carbon (≤0.03%) avoids intergranular corrosion during welding, and has passed ISO 13485 biocompatibility certification, meeting the safety standards of medical devices.

What do the surfaces 2B, BA and No.4 of stainless steel plate represent?

2b is the matte surface of pickling after cold rolling; BA is a bright annealed mirror; No.4 is 180# ground silk grain surface, which is commonly used in architectural decoration.

What is the difference between Q：Z60 and Z180 galvanized coatings?

Z60 stands for double-sided 60g/㎡ (about 8.6μm), which is used in indoor dry environment; Z180 (180 g/≈ 25.7 μ m) is used outdoors, and its salt spray resistance time is more than 1000 hours.

How to deal with white rust on galvanized sheet?

This is zinc oxide product (ZnO), which can be wiped with 5% acetic acid solution (pH3), and it needs to be ventilated to avoid condensation during storage.

Can galvanized sheet be welded directly?

It needs special craftsmanship! Suggestions: ① Use silicon bronze welding wire (Cusi3); ② The welding current is 15% higher than that of carbon steel; ③ Brush with zinc-rich paint to repair immediately after welding.

Which is more corrosion resistant, galvalume or galvanized?

Galvalume (55% Al-Zn alloy) has 2-4 times the corrosion resistance of pure galvanized sheet, especially in the industrial atmosphere containing SO, its service life is over 30 years.

How to detect the thickness of galvanized layer?

The first choice is the magnetic thickness gauge (error 3 μ m), and it is necessary to avoid the edge of the plate by 50mm when measuring, and take an average of 9 points (refer to GB/T 13912 standard).

Which is suitable for hull, 5052 or 6061?

5052 (Al-Mg series) has better seawater corrosion resistance, and its yield strength is 145MPa；. 6061(Al-Mg-Si system) has higher strength (240MPa) but slightly poor corrosion resistance.

How to eliminate orange peel on the surface of aluminum plate?

Due to coarse grains, the annealing process needs to be controlled: ①300 series annealing temperature is 350 10℃; ② 5000 series requires 260℃ slow cooling (cooling rate ≤30℃/h).

Why does aviation aluminum have to use 7075?

After T6 treatment, the tensile strength of A: 7075 (Al-Zn-Mg-Cu) is 572MPa, 80% higher than that of 6061, and the fatigue limit is 240 MPa (10 7 cycles).

What about wrinkling during transportation in aluminum coil?

The requirements are as follows: ① The diameter of the winding core is ≥ 1/3 of the plate width; ② The tension is controlled at 0.2-0.5 MPa; ③ A V-shaped frame (with an included angle of 60) is used for transportation.

How to choose the anodic oxidation film thickness?

AA10 (10μm) for decoration, AA15 (15μm) for outdoor buildings and AA20 (20μm) or above for military products.

What is the difference in conductivity between Q：T2 copper and TU1 oxygen-free copper? What is the difference between the applicable scenarios?

Tu1 oxygen-free copper (oxygen content ≤0.001%) has a conductivity ≥101%IACS, which is 3% higher than that of T2 red copper (oxygen content 0.03%, conductivity 98%IACS). TU1 must be used for high-frequency electronic devices (such as 5G waveguide), and T2 can be used for ordinary power transmission (in line with GB/T 5231 standard).

How to avoid blackening and oxidation when welding copper pipes?

Welding with nitrogen protection: ① Nitrogen flow ≥ 15L/min when the pipe diameter is ≤50mm; ② Scrubbing with 10% citric acid solution immediately after welding; ③ Passivation treatment (BTA benzotriazole solution is recommended).

Why does Q：H62 brass crack easily? How to prevent it?

The zinc content of A：H62 is 40% in the "brittle zone", and the cold working deformation should be ≤30%. Annealing before stamping: heating to 600℃ for 1 hour, cooling to 300℃ and air cooling (refer to YS/T 649 process).

Which scenarios are suitable for phosphorus deoxidized copper (such as TP2)?

0.015-0.04% phosphorus, 50% high temperature oxidation resistance, specially used for:
Boiler condenser tube (resistant to 300℃ steam) Medical gas pipeline (no oxide shedding pollution) Base metal for welding (fluidity is better than ordinary copper)

How to quickly detect the purity of copper?

Two-step preliminary judgment:
Resistivity method: Measure the resistivity with micro-ohm, and Tu1 ≤ 0.01707 Ω mm/m (20℃). Pickling method: when the sample is immersed in 50% nitric acid, uniform and fine bubbles are generated on the surface of high-purity copper, while the bubbles of impurity copper are coarse and uneven.