269 lines
8.6 KiB
HTML
269 lines
8.6 KiB
HTML
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<!DOCTYPE html>
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<meta name="viewport" content="width=device-width, initial-scale=1.0">
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<title>Heat Budget | Bernardo Zubko</title>
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<meta property="og:title" content="Heat Budget | Bernardo Zubko">
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<meta name="description" content="A weld isn’t a joint. It’s a transient thermal event. The arc deposits energy. The base metal steals it away. The race between input and bleed determines…">
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:root {
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--bg: #0a0a0a;
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border-top: 1px solid var(--dim);
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padding-top: 2rem;
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margin-top: 4rem;
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font-family: var(--mono);
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.back-link {
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display: inline-block;
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margin-bottom: 2rem;
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text-decoration: none;
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</style>
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<script defer src="https://analytics.4ort.xyz/script.js" data-website-id="d3ed927c-888a-4a6c-ae5f-0b1c613ddf5b"></script>
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</head>
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<body>
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<header>
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<h1>Heat Budget</h1>
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<div class="breadcrumb"><a href="index.html">← Home</a> / Energy Flow Through Steel</div>
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</header>
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<main>
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<article>
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<section>
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<h2>01. The Law of the Puddle</h2>
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<p>A weld isn’t a joint. It’s a transient thermal event. The arc deposits energy. The base metal steals it away. The race between input and bleed determines whether the bead fuses or cracks.</p>
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<p>We call it the Heat Input Equation. It’s not theory. It’s the reason your root pass collapses in the wind.</p>
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<div class="equation">
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<span class="variable">Q</span> = (<span class="variable">E</span> × <span class="variable">I</span> × <span class="variable">η</span>) / <span class="variable">v</span>
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<div class="unit">
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<br>Q = Heat Input [J/mm]<br>
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E = Voltage [V]<br>
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I = Current [A]<br>
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η = Efficiency (0.8–0.95 for GMAW)<br>
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v = Travel Speed [mm/s]
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</div>
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</div>
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<p>In the shop, I don’t calculate this with a calculator. I feel it in the hum. Slow travel? More heat. Fast drag? Less. But the math is the same. And when the wind hits, <span class="variable">η</span> drops because convective loss spikes.</p>
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</section>
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<section>
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<h2>02. Conductivity as Destiny</h2>
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<p>Material choice is thermal destiny. Mild steel conducts at ~50 W/(m·K). Aluminum screams at ~200+. Cast iron crawls at ~40. Change the alloy, change the budget.</p>
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<table class="data-table">
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<thead>
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<tr>
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<th>Material</th>
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<th>Conductivity [W/(m·K)]</th>
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<th>Specific Heat [J/(kg·K)]</th>
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<th>Density [kg/m³]</th>
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</tr>
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</thead>
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<tbody>
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<tr>
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<td>Mild Steel (A36)</td>
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<td>50</td>
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<td>490</td>
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<td>7850</td>
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</tr>
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<tr>
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<td>Carbon Steel (1045)</td>
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<td>46</td>
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<td>500</td>
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<td>7850</td>
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</tr>
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<tr>
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<td>Stainless 304</td>
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<td>16</td>
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<td>500</td>
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<td>7900</td>
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</tr>
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<tr>
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<td>Aluminum 6061</td>
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<td>200</td>
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<td>897</td>
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<td>2700</td>
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</tr>
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<tr>
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<td>Cast Iron (Gray)</td>
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<td>40</td>
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<td>460</td>
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<td>7200</td>
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</tr>
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</tbody>
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</table>
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<p>Notice stainless? Low conductivity means heat stays local. That’s why it warps less—but also why it burns through if you don’t feather the arc.</p>
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</section>
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<section>
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<h2>03. Diffusion Geometry</h2>
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<p>Heat doesn’t spread evenly. It follows Fourier’s law: flux proportional to the negative gradient.</p>
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<div class="equation">
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<span class="variable">q</span> = −<span class="variable">k</span> ∇<span class="variable">T</span>
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<div class="unit">
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<br>q = Heat Flux [W/m²]<br>
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k = Thermal Conductivity<br>
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∇T = Temperature Gradient
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</div>
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</div>
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<p>In practice: preheat reduces the gradient. No preheat? The gradient is a cliff. The metal fractures trying to climb it.</p>
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</section>
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</article>
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<aside>
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<figure>
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<img src="https://images.pexels.com/photos/38251244/pexels-photo-38251244.jpeg?auto=compress&cs=tinysrgb&dpr=2&h=650&w=940" alt="Topographic contour visualization representing thermal diffusion gradients in a welded plate">
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<figcaption class="caption">Fig 1. Iso-thermic contours visualizing heat diffusion from a point-source arc. Purple = peak temp (>1500°C). Blue = fusion boundary (~1500°C). Grey = unaffected base metal.</figcaption>
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</figure>
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<section>
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<h2>Field Note</h2>
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<p>Black Hills, winter. Wind from the west at 22 km/h. Plate: 6mm A36. Preheat: none. Result: undercut on the leeward side. The wind stole 15% of <span class="variable">η</span>.</p>
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<p>Lesson: When the prairie blows, preheat or die.</p>
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</section>
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</aside>
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</main>
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<footer>
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<a href="index.html" class="back-link">← Back to Home</a>
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<br><br>
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Data sourced from ASM Handbook Vol 1 & ISO 4063 standards.<br>
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