Yes, a chrome-plated or induction-hardened rod can be welded, but not through the chrome or through the hardened case. The joint is made to the base steel, so the coating is removed locally, the case and the base condition at the weld have to be allowed for, and the welding procedure has to be stated on the drawing.
Can you weld a chrome-plated or induction-hardened rod at all?
Yes. The weld is made to the base steel, not to the chrome layer and not to the hardened case, and the finished shaft still has to meet the drawing. What changes compared with welding a plain ground bar is preparation and procedure: the coating has to be removed from the surfaces that will be welded, and the condition of the material under and around the weld has to be specified.
Two facts drive that. Hard chrome is a coating applied at a thickness chosen per order; it is not intended to carry a weld. An induction-hardened bar, in turn, has a defined depth of hardened material below the surface, and welding changes it. As general welding practice, welding surfaces should be cleaned of any coating that could create toxic exposure, and Cr(VI) fume is highly toxic and can cause cancer. Hard chrome is a chromium coating, so no welding should be done through it.
Welding on a chrome-plated or induction-hardened shaft therefore changes the chrome, the hardened case and the base condition at the weld, and needs its own welding procedure stated on the drawing. That is the practical answer to the title question.
What happens to the chrome, the case and the base at the weld?
All three are affected. The chrome layer is destroyed in the weld zone, the hardened case is changed, and the base within the heat-affected zone (HAZ) is no longer in the condition it was supplied in.
Most of the metallurgical risk sits in the HAZ. Higher carbon and alloy content and thicker sections raise HAZ hardness and hydrogen-cracking risk. Preheat reduces the cooling rate, promotes hydrogen escape and lowers HAZ hardness. Low-hydrogen processes and consumables should be used, with post-weld heat treatment where needed.
There is a second effect in quenched-and-tempered steels: the weld thermal cycle can also soften parts of the HAZ, and the softened zone widens as heat input rises. A welded rod can therefore carry a hard, crack-prone zone next to a softer one, both inside the region that has to take load.
On a chrome-plated bar the surface adds a third item. At Yixin Precision Machinery (Changzhou) the hard chrome layer is 10–50 μm per side, chosen per order on the drawing, and it cannot survive the arc. The width of the chrome-free zone at the welded end, and whether the area is re-plated afterwards, belong on the drawing rather than in a verbal instruction to the welding shop.
Which rod should you start from if the ends will be welded or machined?
Start from the base condition the joint needs, then treat the chrome as a surface that is removed and (if required) restored. When the rod ends need heavy machining, or the load calls for a quenched-and-tempered base, the matching products are the Q&T chrome-plated bars in 45, 40Cr and 42CrMo. Where the rod surface takes the wear and guidance load and little machining follows after supply, a soft or induction-hardened chrome shaft is the usual starting point.
| Rod to start from | Base condition at the welded end | What it means for the weld |
|---|---|---|
| 45 Steel Chrome-Plated Soft Shaft | Grade 45, not induction hardened, base about HRC17 | The weld sees the softest base in the range; the chrome still has to be removed locally before welding. |
| 45 Steel Induction-Hardened Chrome Shaft | Induction-hardened case ≥ HRC55, about 2 mm deep | The case and the chrome are both changed by the weld thermal cycle; the weld must not be made through the case. |
| 45 Steel Q&T Chrome-Plated Bar | Quenched-and-tempered base, surface hardness HRC25–28 or HRC28–32 chosen per order, with a softer core | A Q&T base under the chrome, and no induction-hardened case; this is the base to specify when the rod ends will be machined after supply. |
| 40Cr Q&T Chrome-Plated Bar and 42CrMo Q&T Chrome-Plated Bar | Q&T base, made to order | Different chemistry from grade 45; write and qualify the welding procedure for the grade actually ordered. |
The rule that does not change is the sequence: prepare the joint area, weld to the base steel, then restore the surface if the drawing requires it.
What should the welding procedure on the drawing contain?
The drawing should fix the base grade and condition, the chrome-free zone, the welding process and consumables, the preheat and post-weld heat treatment requirements, and the acceptance limits for the weld and the HAZ. Without those five items two suppliers will deliver two different joints, and neither can be checked against a specification.
Heat input is the variable that links them. Preheat reduces the cooling rate, promotes hydrogen escape and lowers HAZ hardness; higher carbon and alloy content and thicker sections raise HAZ hardness and hydrogen-cracking risk; low-hydrogen processes and consumables should be used, with post-weld heat treatment where needed. Because the softened zone in a quenched-and-tempered HAZ widens as heat input rises, the drawing should also say whether heat input is controlled and recorded.
Sequence matters as much as parameters. Welding before plating keeps the arc away from a finished coating; when a bar is supplied already chrome plated, the chrome has to be stripped from the joint area first. State on the drawing which operation comes first, which zone may be left bare, and whether the welded end has to be re-plated and re-polished afterwards.
How should the welded joint be inspected?
Inspect the weld and the HAZ against the acceptance limits written on the drawing, and confirm that no chrome remains in the joint area.
Hardness in the HAZ is the usual measurable check for the risks described above, so the drawing should state the limit and the method. Hydrogen cracking may not be visible immediately after welding, so the drawing should also state when inspection takes place and whether it is repeated later. Around the weld, check that the chrome-free zone matches the width on the drawing, that the coating edge is clean, and that no chrome has been left inside the welded area.
Finally, check the shaft itself: diameter over the welded end, total length, and straightness after welding if the drawing calls for a straightened bar. Third-party inspection of an order can be arranged on request; the steel mill certificate covers the bar as supplied, not the weld.
What to put in your RFQ
- State that the rod end will be welded, and whether welding happens before or after final machining and chrome plating.
- Give the base grade and condition: grade 45, 40Cr or 42CrMo, and whether a soft, induction-hardened or quenched-and-tempered base is required.
- Give the width of the chrome-free zone at the welded end, and the chrome thickness required per side (chrome 10–50 μm per side, plated by Yixin's partner plants to Yixin's specification, chosen per order).
- State the welding process, the consumables, whether preheat is required and whether post-weld heat treatment is required.
- State the acceptance limits for the weld and the heat-affected zone, including any hardness limit and the inspection method.
- State whether the welded area must be re-plated and re-polished, and the surface finish required.
- Give diameter, tolerance and cut length, and the straightness requirement after welding.
Summary
A chrome-plated or induction-hardened rod can be welded, but the weld is made to the base steel. Three things have to be settled before the bar is ordered: which base condition the joint needs, how wide the chrome-free zone at the welded end must be, and what the welding procedure allows in the HAZ. The chrome layer, the induction-hardened case and the base condition are all changed by the weld thermal cycle, so the procedure, the preheat and post-weld heat treatment, and the acceptance limits belong on the drawing. If the rod ends need heavy machining or the load calls for a quenched-and-tempered base, start from a 45, 40Cr or 42CrMo Q&T chrome-plated bar rather than an induction-hardened one.
References
- GB/T 699-2015 — named in the Yixin catalogue as the standard for grade 45.
- GB/T 3077-2015 — named in the Yixin catalogue as the standard for 40Cr and 42CrMo.