What Is the Melting Point of Stainless Steel?

Stainless steel is an iron-based alloy containing chromium. It is widely used in various environments due to its excellent rust and corrosion resistance. The performance of stainless steel can be further enhanced by adding alloying elements such as molybdenum, carbon, nickel, and nitrogen to meet specific usage requirements. The addition of these alloying elements not only changes the microstructure of the material, but also affects its melting point. Understanding the melting points of different grades of stainless steel is important for ensuring its safe application in high-temperature environments and formulating reasonable processing processes. This article will explore the melting point of stainless steel in depth. I hope that after reading it, you can choose stainless steel materials that have both high-temperature performance and cost-effectiveness according to the actual temperature conditions of the project.

If you are preparing to purchase a batch of stainless steel materials, whether it is stainless steel pipes, stainless steel bars, stainless steel plates, or stainless steel profiles, we can provide you with professional solutions and high-quality products. Welcome to contact us for technical support, material selection suggestions and the latest quotes.

What Is the Melting Point

The melting point (or rare liquefaction point) of a substance is the temperature at which it changes from solid to liquid. At the melting point, the solid and liquid phases are in equilibrium.

Why Do We Need to Know the Melting Point of Stainless Steel

The melting point of stainless steel is not a simple physical parameter, but a key indicator throughout the entire industrial production chain. From raw material selection to finished product application, melting point data provides engineers and technicians with important decision-making basis:

Material Selection

The difference in melting point of stainless steel of different steel grades determines their applicable temperature scenarios, avoiding high-temperature softening or oxidation failure;

Process Selection

During welding, casting or heat treatment, the temperature must be close to but not exceed the melting point;

Safety Assurance

In the chemical or construction fields, the melting point determines the tolerance limit of the material in a fire or high-temperature environment, preventing the structure from melting through or deforming;

Cost Control

The processing energy consumption of high-melting-point stainless steel is higher, and a reasonable choice can balance performance and economy;

How to Measure the Melting Point of Stainless Steel

The determination of metal melting point is an important link in materials science and metallurgical industry, especially in alloy design, casting and high-temperature application fields. The current mainstream melting point determination methods are as follows:

Differential Scanning Calorimetry (DSC)

DSC determines the melting point of a metal by accurately measuring the heat flow difference between the sample and the reference. The core principle is: during the program temperature control process, when the metal sample reaches the melting point, the crystal structure needs to absorb heat to destroy. At this time, the instrument detects the heat flow change on the sample side and records it as an endothermic peak on the DSC curve. In actual measurement, the intersection of the tangent line of the endothermic peak front and the baseline (onset temperature) is usually used as the theoretical melting point value. This parameter is closest to the thermodynamic equilibrium melting point; while the peak temperature of the endothermic peak (peak temperature peak) reflects the kinetic characteristics of the melting process, which is generally slightly higher than the actual melting point.

Thermocouple Direct Measurement

Thermocouple direct measurement is a contact temperature measurement technology based on the principle of thermoelectric effect. This method uses two different metal conductors (such as platinum-rhodium alloy) to form a closed loop. When the measuring end contacts the high-temperature molten metal, the Seebeck effect will generate a thermoelectric potential (millivolt signal) proportional to the temperature. The real-time temperature can be determined by the pre-calibrated temperature-potential curve.

In terms of melting point determination, it is mainly based on two characteristics: First, when the metal reaches the melting point during the heating process, the phase change absorbs heat, which will cause a short temperature platform in the thermocouple reading; second, when the metal is completely melted into liquid, the contact state between the thermocouple measuring end and the melt changes, which often leads to a significant jump in the temperature curve. In order to improve the reliability of measurement, it is usually necessary to cooperate with visual observation or video monitoring to confirm the melting state of the metal.

This method has the advantages of fast response (seconds) and simple implementation, but it is necessary to select high-temperature resistant thermocouple materials (such as platinum-rhodium thermocouples can measure up to 1600℃) and install protective sleeves to prevent corrosion. Its typical measurement accuracy is ±1-5℃, which is particularly suitable for real-time temperature monitoring needs in industrial sites such as casting and metallurgy.

High-Temperature Optical Method

The high-temperature optical method detects the intensity of visible light or infrared radiation emitted by the metal when it is heated, and uses the law of thermal radiation (Planck’s law) to convert the optical signal into a temperature value. The higher the metal temperature, the stronger the radiation intensity and the change in wavelength characteristics.

The high-temperature optical method mainly conducts a comprehensive analysis of three characteristic changes to determine the melting point of the metal.

The most direct criterion is to monitor the sudden change of the radiation characteristics of the metal surface: when the solid metal begins to melt, its surface emissivity will change significantly by 10-20%, which is manifested as an obvious inflection point feature on the real-time temperature-time curve.

At the same time, the transformation process of the metal surface morphology can be observed with the high-speed camera system. The solid surface shows diffuse reflection characteristics, while the melted liquid metal will produce typical mirror reflection phenomenon. This change in optical characteristics can be used as intuitive evidence of melting.

For high-precision measurement, the dual-wavelength ratio method using a colorimetric pyrometer is particularly effective. This method simultaneously monitors the radiation intensity ratio of the red and blue characteristic bands, and a transition change of the ratio is observed at the melting point. This method can effectively reduce the interference of factors such as the oxide layer on the metal surface.

By combining these judgment methods, the high-temperature optical method can achieve a typical reading accuracy of ±3-5°C for the melting point measurement of refractory metals above 1500°C, which is particularly suitable for the online real-time detection needs in the metallurgical industry.

Melting Point of Stainless Steel

Stainless steel is a large family of materials that includes a large number of steel grades with different alloying additions. The melting point of stainless steel varies mainly between 1,325 and 1,530 °C (2,417 and 2,786 °F). Stainless steel is classified based on its microstructure as austenitic stainless steel (such as 304, 316, and 317), ferritic stainless steel (such as 430 and 434), and martensitic stainless steel (such as 410 and 420).

The following is a list of common stainless steel alloys and their melting temperatures

Grade	EN Specification	Melting Point
1.4301	301	1400 – 1420°C
1.4305	303	1400 – 1420°C
1.4301	304	1400 – 1450°C
1.4307	304L	1400 – 1450°C
1.4845	310	1400 – 1450°C
1.4401	316	1375 – 1400°C
1.4404	316L	1375 – 1400°C
1.4541	321	1400 – 1425°C
1.4016	430	1425 – 1510°C

For more information about the melting point of metals, please refer to this article: Ultimate Guide to Melting Points of Metals

Why Is the Melting Point of Stainless Steel Expressed in Intervals?

You must have noticed that the melting points of the above-mentioned common stainless steel grades are expressed in temperature intervals, not absolute values. This is because, as a high-alloy steel, the performance of stainless steel depends on the precise ratio of multiple alloying elements. According to international standards (such as ASTM, GB, etc.), each element (such as Cr, Ni, Mo, etc.) has a clear content range (such as Cr 18-20%), and a slight tolerance (usually ±0.5-1%) is allowed during production to ensure that the material can adapt to process fluctuations while meeting the standards.

The following is the alloy composition of 304, 304L, 316, 316L under the ASTM A312 standard. We will find that their chromium, nickel, and molybdenum components are all expressed in intervals. Slight changes in alloy composition will cause changes in the melting point of the material.

Grade	UNS Designation	Carbon	Manganese	Phosphorus	Sulfur	Silicon	Chromium	Nickel	Molybdenum
TP304	S30400	0.08	2	0.045	0.03	1	18.0-20.0	8.0-11.0
TP304L	S30403	0.035	2	0.045	0.03	1	18.0-20.0	8.0-13.0
TP316	S31600	0.08	2	0.045	0.03	1	16.0-18.0	11.0-14.0	2.00-3.00
TP316L	S31603	0.035	2	0.045	0.03	1	16.0-18.0	10.0-14.0	2.00-3.00

Factors Affecting the Melting Point of Metals

In addition to the alloying and impurities mentioned above, the melting point of metals is also affected by the following factors:

Interatomic Bonding

The strength of the metal bond is the key to determining the melting point. Metals with smaller atomic radius and more valence electrons (such as tungsten and tantalum) have stronger metal bonds and higher melting points because the nuclear charge has a stronger attraction to electrons; while alkali metals (such as sodium and potassium) have weaker metal bonds and lower melting points because of their large atomic radius and fewer valence electrons;

Crystal Structure

Common crystal structures of metals include body-centered cubic structure (BCC), face-centered cubic structure (FCC), and hexagonal close-packed structure (HCP). The atomic packing density of face-centered cubic structure and hexagonal close-packed structure is 74%, which is higher than the 68% of body-centered cubic structure. A tighter packing structure usually means that the distance between atoms is closer and the bond is stronger, which may lead to a higher melting point. However, it is also necessary to emphasize that the melting point of metals is affected by many factors. We cannot simply assume that the melting point of metals with HCP and FCC structures must be higher than that of metals with BCC structures. We can get a glimpse of this from the melting points of the following common metals.

Common metals with HCP crystal structure: magnesium (650℃), zinc (419.53℃), titanium (1668), cobalt (1495℃), etc.;

Common metals with FCC crystal structure: aluminum (660.32℃), copper (1084.62℃), gold (1064.18℃), nickel (1455℃), etc.;

Common metals with BCC crystal structure: chromium (1907℃), tungsten (3422℃), molybdenum (2623℃), vanadium (1910℃), etc.;

External Pressure

The melting point of materials is also affected by external pressure. Here we would like to cite the Clapeyron equation (as described below), which is mainly used to analyze the thermodynamics of phase change.

$\frac{dP}{dT} = \frac{\Delta H_m}{T \Delta V_m}$

In the above equation:

$\frac{dP}{dT}$ represents the slope of the phase equilibrium curve, that is, the rate of change of pressure $P$ with temperature $T$ ;
$\Delta H_m$ is the molar phase change enthalpy (such as melting enthalpy, vaporization enthalpy), in J/mol;
$T$ is the phase change temperature (such as melting point, boiling point), in K;
$\Delta V_m$ is the molar volume change (that is, the volume after the phase change minus the volume before the phase change), in m³/mol.

Let’s go back to the relationship between the melting point and pressure of metals. Let’s analyze the above factors. Most metals expand in volume when they melt, so $\Delta V_m > 0$ . $\Delta H_m$ refers to the heat absorbed by 1 mol of solid to completely transform into liquid at the melting point ( $T_m$ ), and its value is always positive. Therefore, $\Delta H_m > 0$ . $T$ is the phase change temperature, so it is also greater than 0.

In summary, $\Delta V_m > 0$ , $\Delta H_m > 0$ , $T > 0$ , so we get $\frac{dP}{dT} > 0$ . So we conclude that if we increase the pressure ( $dP > 0$ ), $dT$ must also be $> 0$ . Therefore, we finally conclude that increasing the external pressure will increase the melting point.

However, some materials are special, and increasing the external pressure will reduce the melting point. In the above analysis, $\Delta V_m > 0$ is a very critical value. This is based on the fact that in the melting process of conventional metal materials, the volume of metal increases when it changes from solid to liquid. However, the melting of some materials, such as bismuth (Bi) and antimony (Sb), is different. Although these two metals also change from solid to liquid when they melt, their volume will shrink because of their special crystal structure. In this case, $\Delta V_m < 0$ , $\Delta H_m > 0$ , $T > 0$ , so $\frac{dP}{dT} < 0$ . If the pressure is increased ( $dP > 0$ ), $dT$ is $< 0$ .

Obtain Stainless Steel Material Solutions from HYT

In practical applications under high temperature conditions, melting point is an important parameter to consider when selecting stainless steel materials or manufacturing technology. If you still have concerns about the selection of stainless steel materials with high melting points, HYT can provide you with professional stainless steel material solutions. Whether it is stainless steel pipes, stainless steel plates, or stainless steel bars, HYT can achieve mass production and fast supply. Welcome to contact our HYT technical team for solutions.

Introduction