Calculate the Bruscato X factor for Cr–Mo weld-metal screening from phosphorus, antimony, tin and arsenic mass concentrations in ppm or weight percent. This index does not establish toughness, welding suitability or specification compliance.
- All Construction Calculators
- Von Mises Stress Calculator
- PPM Calculator
- Brinell Hardness Number Calculator w/ Formula
- Heat Input Calculator
- Welding Machine Load Calculator
- Welding Machine Amperage Calculator
X Factor Formula
The Bruscato X factor is calculated from phosphorus, antimony, tin and arsenic concentrations by mass. All four inputs are converted to ppm by mass before the calculation. The formula and Cr–Mo weld-metal scope are described by TWI. Apply any procurement threshold and required tests separately.
If an input is entered as a percent, the calculator first converts it to ppm:
- X = X factor
- P = phosphorus content in ppm
- Sb = antimony content in ppm
- Sn = tin content in ppm
- As = arsenic content in ppm
- C_percent = concentration entered as a percent
- C_ppm = concentration converted to parts per million
The calculator accepts each element in either ppm by mass or weight percent; it does not accept atomic percent, volume percent or mg/L. If you choose ppm, the value is used directly. If you choose percent, the value is multiplied by 10,000 to convert it to ppm. The converted values are then weighted in the X factor formula. Phosphorus has the largest weight, followed by antimony, tin, and arsenic.
X Factor Input Conversion Reference
Use this table to check how percent values relate to ppm values before they are used in the X factor calculation.
| Percent | ppm Equivalent | Conversion |
|---|---|---|
| 0.001% | 10 ppm | 0.001 × 10,000 |
| 0.005% | 50 ppm | 0.005 × 10,000 |
| 0.010% | 100 ppm | 0.010 × 10,000 |
| 0.050% | 500 ppm | 0.050 × 10,000 |
| 0.100% | 1,000 ppm | 0.100 × 10,000 |
X Factor Example
Example 1: All inputs in ppm
Suppose you have these values:
- Phosphorus = 80 ppm
- Antimony = 20 ppm
- Tin = 30 ppm
- Arsenic = 10 ppm
The X factor is 10.3000.
Example 2: Mixed ppm and percent inputs
Suppose phosphorus is entered as a percent and the other values are entered in ppm:
- Phosphorus = 0.006% = 60 ppm
- Antimony = 15 ppm
- Tin = 25 ppm
- Arsenic = 8 ppm
The X factor is 7.8300.
X Factor Calculator FAQ
What does the X factor measure?
The Bruscato X factor is an empirical composition index used in screening Cr–Mo weld metals for susceptibility to temper embrittlement. A higher number means a higher weighted trace-element concentration in this model; it is not a direct measurement of toughness or a universal pass/fail result.
Do I need to enter every element?
Yes. Enter all four concentrations. Zero is valid only when it is the intended measured or explicitly assumed concentration. A below-detection result is not necessarily zero: use the laboratory’s reported limit for a labeled upper-bound scenario if appropriate, or obtain a quantitative result. The calculator does not infer missing chemistry.
Why is phosphorus weighted more heavily than arsenic?
The formula assigns different weights to each element. Phosphorus is multiplied by 10, antimony by 5, tin by 4, and arsenic by 1. This means phosphorus has the largest effect on the final X factor for the same ppm concentration.
