Materials / Reference and confirmation
RUNSU reviews carbon, alloy and engineering steels against the drawing, standard and end use. A familiar grade name starts the conversation; the purchase specification finishes it.
01 / Material families
The family narrows the material conversation. It does not replace the standard, condition or drawing.
General machinery, structural parts, pipe and bar stock. Where formability and general mechanical requirements dominate, carbon steel is often the starting family; the exact grade still follows the drawing and application.
20# · 35# · 45# · 50# · Q235 · Q355
Higher strength, wear resistance, toughness, hardenability or heat-treatment response can call for an alloy steel. These references are reviewed with the treatment condition — not as a name-only substitution.
20Cr · 40Cr · 20CrMnTi · 35CrMo · 42CrMo · 38CrMoAl
Shafts, gears, rollers, pins, sleeves and custom machined parts bring the intended process into the material decision. Forging, machining and heat treatment belong in the same review.
Drawing-led · treated · machined
02 / Reference board
The grades below are references named in the published company material. They are starting points for discussion. Product form, standard edition, condition and quantity determine what can be offered.
| Reference family | Original grades / references | Usual discussion | To confirm |
|---|---|---|---|
| Carbon steel (Chinese) | 20#, 35#, 45#, 50# | General machinery, pipes, bars and parts | Standard, condition, inspection and product form |
| Structural carbon | Q235, Q355 | Structural pipe and fabrication requirements | Standard edition, dimensions and acceptance points |
| Chromium alloy | 20Cr, 40Cr, 20CrMnTi | Components needing hardenability or wear resistance | Heat-treatment route, hardness and drawing |
| Molybdenum alloy | 35CrMo, 42CrMo, 38CrMoAl | Higher-strength shafts, bars and treated parts | Mechanical properties, condition and test scope |
| AISI / SAE references | 1020, 1045, 4130, 4140, 4340, 8620 | Comparison with American practice | Exact standard, chemistry and property requirements |
| European references | C45, CK45, EN8, EN19, EN24, 16MnCr5 | Comparison with European practice | Exact EN / DIN designation and condition |
| Other references | E355, S355, SCM415, SCM440, SNCM439, 34CrNiMo6, 36CrNiMo4 | Project or drawing-specific discussion | Named standard and customer specification |
No stock size range is implied by this page. Availability, tolerances and documentation are confirmed against the actual inquiry and agreed order.
03 / Selection discipline
A grade reference is not a complete requirement. The same name can be supplied in different conditions, under different standards, or for a different product form. The review therefore moves through the same fixed points before an alternative is proposed.
This is also why two familiar grades are not treated as interchangeable by default. The buyer's drawing and purchase specification remain the basis of the order.
A grade name has value only when read with its standard, condition and product form. Those three points are confirmed in writing before quotation.
04 / Equivalence
Grade references from different systems can look close on paper. They may still differ in chemical composition, mechanical properties, heat-treatment condition, tolerances and supply form.
RUNSU treats every equivalence as a comparison to be checked against the drawing and purchase specification. No substitution is automatic, and any proposed alternative is confirmed with the buyer before it is used.
05 / Standards
Standards are part of the requirement, not a shorthand for it. State the exact designation and edition where the order depends on acceptance criteria.
A standard can be discussed for pipes, bars and shaft materials. The final applicability of a standard to the ordered product, dimensions and documents is confirmed in the quotation.
Procurement FAQ
These are the grade questions buyers ask most often. Each answer ends at the same point: the drawing and purchase specification govern the order.
Send the product form, grade or standard, size, quantity, treatment requirement and destination. If the grade is uncertain, include the application and the load or property requirement.
