How Do You Braze Wire Rope?
A saying states that a chain is only as strong as its weakest link. The same applies to wire ropes used in conjunction with other lifting gear. By carefully brazing your wire rope, you can strengthen it and ensure that it does not fray or cause damage to you or any of the mechanisms used in lifting gear.
Brazing wire rope involves heating a filler metal to just above its fusion temperature, then allowing the molten filler metal to spread into the end of the wire rope with the aid of brazing flux. Once cooled, the brazed rope end or joint can be cleaned and shaped according to its purpose.
Brazing is similar to soldering, except at higher temperatures than soldering. With a few simple tools and supplies from your local hardware store, including the relevant safety gear, you can easily braze your wire ropes – from hoisting gear to bike cable repairs.
The Process Of Brazing Wire Rope
The metal filler used in brazing must have a lower melting point than the base metal in the rope, so it is a good idea to ascertain what type of rope you have before choosing a filler. Steel is used in many heavy-duty wire ropes and has a melting point of between 2500 to 2800°F.
The more popular metal fillers are silver, copper, and aluminum alloys. Silver alloys are more costly but have a relatively low melting point (1300°F). Copper alloys have a higher melting point (2000°F) and are more cost-effective. Aluminum alloys melt at 1080°F and will only braze with aluminum.
There are a few different ways to braze metals, but for small assemblies and applications like wire ropes, free-hand or dip brazing is more than sufficient. Whether you want to neaten up the ends of a wire rope or join two wire ropes, you will need the following:
- Wire rope to be brazed,
- A hand-held torch (propane or oxygen-acetylene torch),
- A suitable flux for the metals involved (flux comes in liquid, powder, or paste form),
- A suitable filler metal,
- A fire-safe surface on which to work,
- A fire-safe container large enough to melt the filler metal and for dipping,
- Supports, e.g., vices and clamps that are poor heat conductors, and
- Protective gear, including gloves and safety glasses.
Step 1: Clean The Wire Rope Section To Be Brazed
Clean the wire rope you want to braze as it needs to be free of impurities and oxidation. You can scrub it with sandpaper to remove the oxidation, then acetone to remove any grease. If there is dirt, you can use soap and water to clean it, then leave the metal to air dry.
Step 2: Prepare Your Brazing Workspace And Tools
Set out your tools and supplies for easy access on your fire-safe surface. If dip-brazing the tips of a long or heavy wire rope, ensure the rest of the rope length is clamped or secure to prevent it from sliding or falling during the brazing process.
If you are brazing two wires together, make sure they are spliced and clamped into place before you start heating things.
Step 3: Apply Brazing Flux To The Wire Rope
Since you will likely be brazing in an open-air environment (as opposed to a controlled atmosphere or vacuum environment), you will need to apply flux to the wire rope. The purpose of flux is to prevent oxidation caused by the heating process, preserve the filler metal and assist it in flowing into the small gaps by capillary action.
The flux can be applied just before the heating process begins, and once heated, it needs to be in a liquid form before the molten filler metal can be introduced.
Step 4: It’s Time To Heat Things Up
Once your tools and equipment are in place, you can start heating things. If you are into free-hand brazing, watch this link to see how the presenter prepares thick wire rope for a hoist. After brazing the rope tip half an inch, he then explains how to neaten the tips to a “bullet” shape by using a grinder to prevent damaging the hoist and other lifting components.
If you prefer dip-brazing, you can heat the metal filler in its fire-resistant container to get it to a molten state. You can do this by applying a flame to the container or directly to the filler metal. Then, warm up the flux-coated wire rope tip and dip it into the molten filler metal. It will draw up into the tip towards the heat source.
This video shows different ways to braze smaller wire ropes for use in motorized bicycle clutches, brakes, and accelerator cables. The tips are not bullet-shaped but bulbous. Such finishes would be helpful to apply to wire ropes that must not pull through a bracket or beyond a certain length.
If you are joining two wire ropes, the spliced and flux-coated joint must be carefully secured before brazing. The filler metal can be introduced from the top and heated; it will travel into the spaces between the rope fibers with the help of the flux, heat, and capillary action.
The best flame for brazing is a “neutral” flame, one with a blueish to orange tip and blueish-white inner cone. A flame with a colorless tip will likely cause oxidation. The late George Goehl, a metalsmith and sculptor, shared some of his knowledge and how to get the best results of brazing here.
Step 5: Cool Down And Clean Up
Given the likelihood of DIY brazing being in an open-air atmosphere, you should clean the joint or tip to remove flux residue. Flux is chemically corrosive and can weaken the metals in the brazed tip or joint. A hot water quench can be done as soon as the filler metal has solidified to remove flux residue.
If residual oxidation is left on the brazed joint or tip, it can be removed by dipping it into a hot sulfuric or hydrochloric acid solution. However, avoid etching caused by an acidic solution that is too strong.
The Advantages and Disadvantages of Brazing Wire Rope
Below is a table showing five advantages and disadvantages of brazing metal rope.
|1. It is possible to braze different metals together with a filler metal.||1. The tip or join might be a different color, which might not be aesthetically pleasing.|
|2. Brazing does not melt the base metal (rope), preserving its metallurgical characteristics.||2. The joint is not effective at high temperatures due to the lower melting point of the filler metal.|
|3. Brazing offers a clean joint or tip that requires little finishing.||3. Brazing requires a flux, and flux residue needs to be removed.|
|4. Brazed wire rope is corrosion-resistant and, therefore, longer-lasting.||4. If the rope is frayed or not closely spliced, the capillary action of the molten filler won’t work.|
|5. Brazing is fast and less expensive and can be automated.||5. Brazed joints are not as strong as welded joints.|
Wire rope can be brazed to reduce the risk of injury or damage to people and lifting gear. Brazing of wire rope can be done on a domestic or industrial level, using heat, flux, and filler metal. It is an economical way to neaten your wire rope, extend its lifespan, and to prevent jamming your lifting gear.