DW-HF-25kW High Frequency Induction Heating Equipment for Brazing and Hardening

Quick Answer

What is the DW-HF-25kW High Frequency Induction Heating Equipment?

The HLQ DW-HF-25KW-B(A) is a three-phase high-frequency induction heating system designed for industrial brazing, surface hardening, annealing, shrink fitting, soldering, and localized metal heating. The original product page specifies a maximum oscillating-power rating of 25kVA, an operating frequency of 30–80kHz, and a three-phase 380V, 50/60Hz electrical supply. The equipment features a separate main power unit and extension unit, allowing flexible installation in industrial heating stations.

Best-Fit Applications: Copper tube brazing, HVAC fittings, carbide tool brazing, small shaft hardening, selected gear surface hardening, stainless steel heating, bearing assembly, annealing, and localized preheating.

Engineering Selection: The appropriate induction heating equipment must be selected according to workpiece material, effective heated mass, target temperature, required cycle time, operating frequency, induction coil design, and cooling requirements. The published 25kVA rating should not be interpreted as a guaranteed 25kW of useful heat delivered to the workpiece.

Table of Contents

1. What is the DW-HF-25kW High Frequency Induction Heating Equipment?
2. Key Applications
3. Suitable Materials
4. Working Principle
5. Technical Specifications
6. Recommended Model Selection
7. Process Workflow
8. Common Problems and Solutions
9. Engineering Selection Guide
10. Advantages and Limitations
11. Why Choose HLQ?
12. 10 Core FAQs

What is the DW-HF-25kW High Frequency Induction Heating Equipment?

The DW-HF-25kW High Frequency Induction Heating Equipment is an industrial electromagnetic heating system developed for rapid, localized heating of electrically conductive metal components.

It converts incoming three-phase electrical power into high-frequency alternating current. When this current flows through an induction coil, it produces a changing magnetic field that induces electrical currents inside a nearby conductive workpiece.

The resistance of the metal converts the induced currents into heat. Depending on the application, this heat can be used for brazing, hardening, annealing, thermal expansion, or other industrial processes.

Unlike conventional resistance furnaces, induction heating does not necessarily require the entire component to be heated. An appropriately designed coil can concentrate useful heating in the selected region.

The DW-HF-25 series is particularly relevant to manufacturing workshops and production cells that require controlled heating of small and medium-sized metal components.

Main Components of the DW-HF-25 Induction Heating System

Advantages of the Split-Type Construction

The separated equipment arrangement allows the main power unit to be positioned away from the immediate heating area while the smaller extension unit is installed closer to the workpiece.

This arrangement can be beneficial in production environments where heating equipment must be integrated into a workbench, fixture, or manufacturing station.

Key Applications

The DW-HF-25 high-frequency induction heater can be considered for several industrial metal-heating processes.

Each application requires a suitable induction coil, heating temperature, operating frequency, and production procedure.

1. Induction Brazing of Copper Tubes

Induction heating is widely used to raise copper tube joints and compatible fittings to the temperature required for brazing.

The induction coil should heat the joint sufficiently for the selected filler metal to melt, wet the joining surfaces, and flow through the joint clearance.

Typical applications include HVAC refrigeration pipes, air-conditioning copper tubing, heat exchanger connections, and industrial pipe fittings.

Joint preparation, filler selection, and the heating profile are essential for reliable brazing quality.

2. Carbide Tool Brazing

Induction brazing can be used to attach suitable carbide cutting tips to steel holders.

Localized heating allows the brazing region to reach the required temperature while limiting unnecessary heating of surrounding material.

The final process must control joint clearance, filler metal, thermal expansion, and cooling conditions.

3. Steel Shaft Surface Hardening

For suitable carbon and alloy steels, induction heating can rapidly raise selected surface regions to the required austenitizing temperature.

The heated region is then quenched according to an approved heat-treatment procedure.

Final surface hardness and hardened case depth depend on the steel grade, operating frequency, heating time, temperature distribution, and quenching conditions.

4. Gear and Sprocket Hardening

Small gears and sprockets may be heated with appropriately designed induction coils.

Depending on the required hardening pattern, the system may use a circular coil, scanning arrangement, or special-profile inductor.

The heating process should be validated for the specified tooth geometry and hardened depth.

5. Induction Annealing

The machine may be used for selected annealing and localized heat-treatment applications involving steel, copper, brass, and stainless steel components.

The required heating temperature, holding time, and cooling conditions depend on the material and metallurgical objective.

6. Induction Shrink Fitting

Induction heating can produce controlled thermal expansion of steel rings, gears, sleeves, and similar components before assembly.

The temperature must be selected according to the required expansion, material properties, and permissible component temperature.

7. Localized Industrial Preheating

The system may be used for local heating before joining, forming, mechanical assembly, or selected coating operations.

The suitability of the DW-HF-25 depends on the heated area, required temperature, and production cycle.

For application-specific joints and tooling, explore HLQ’s custom induction brazing coils and their engineering design considerations.

Suitable Materials

High-frequency induction heating can be applied to a wide range of electrically conductive materials.

However, each material responds differently because electrical resistivity, magnetic permeability, thermal conductivity, and heat capacity vary with material composition and temperature.

Material Properties Affecting Induction Heating

Working Principle

The DW-HF-25 operates according to electromagnetic induction.

The induction power supply converts incoming three-phase electrical power into alternating current at the selected high-frequency operating point.

The alternating current flows through an induction coil, producing a changing magnetic field around the conductive workpiece.

Electrical currents are induced in the workpiece. Their resistance generates heat within the metal.

The resulting temperature distribution depends on the induction frequency, coil geometry, coupling distance, material properties, and heating time.

High Frequency Induction Heating Process

Induction Frequency and Heating Depth

Operating frequency influences the distribution of induced electrical current inside the metal.

Under simplified conditions, increasing the frequency reduces the reference electrical skin depth.

However, the final temperature penetration depth also depends on heating duration, thermal conductivity, material geometry, and temperature-dependent electromagnetic properties.

The electrical skin depth can be estimated from:

δ = √[ρ / (π × f × μ)]

Where:

• δ = Reference electrical skin depth, m.
• ρ = Electrical resistivity, Ω·m.
• f = Operating frequency, Hz.
• μ = Absolute magnetic permeability, H/m.

Important: Electrical skin depth is not identical to the final temperature penetration depth or hardened case depth.

The original DW-HF-25 page lists an operating frequency of 30–80kHz. Other HLQ product literature lists a wider legacy range for certain DW-HF-25 variants. Final frequency must be confirmed for the specific machine and induction load.

Induction Coil Design

The coil is one of the most important components of an induction heating system.

Its geometry, number of turns, active length, electrical connections, and coupling distance influence electromagnetic heating performance.

For brazing, the coil should provide suitable heating around the joint.

For hardening, the coil should produce the required surface temperature distribution before quenching.

For shrink fitting, heating should provide sufficient and reasonably uniform thermal expansion.

For detailed inductor development, refer to HLQ’s custom induction heating coil design engineering guide.

Technical Specifications

The following technical specifications are based on the original HLQ DW-HF-25 product page.

Some parameters differ from information published on other HLQ pages. Such discrepancies should be resolved in the final equipment datasheet.

DW-HF-25KW-B(A) Technical Specifications

Specification Verification Requirements

Recommended Model Selection

The appropriate induction heating equipment should be selected according to the material, effective heated mass, heating-zone dimensions, target temperature, and required cycle time.

The DW-HF-25 can be considered for small and medium localized heating applications. Larger or heavier components may require a higher-power system or a different operating frequency.

Selection Note: These are preliminary engineering recommendations. The manufacturer does not publish a universal workpiece-size or heating-time guarantee for the DW-HF-25.

For comparison with other power levels, refer to HLQ’s high frequency induction heating power supply product series.

Process Workflow

The industrial induction heating process requires correct workpiece preparation, induction coil selection, electrical matching, heating control, and final quality verification.

General Induction Heating Process

Induction Brazing Process

For brazing, the process involves cleaning the base materials, assembling the joint, positioning a suitable filler metal, applying induction heat, allowing filler-metal flow, and inspecting the completed joint.

The heating process must bring the joint surfaces to the required brazing temperature without intentionally melting the base materials.

Induction Hardening Process

For induction hardening, suitable steel components are heated to the required austenitizing condition and then quenched according to the metallurgical process.

Final hardness and case depth must be verified by appropriate inspection or testing.

For specialized surface-heating components, review HLQ’s induction hardening coil for steel surface hardening solutions.

Cooling System Requirements

The DW-HF-25 is a water-cooled induction heating system.

The complete cooling circuit should provide sufficient heat removal from the induction coil and designated electrical components.

Common Problems and Solutions

High-frequency induction heating performance may be affected by electrical matching, coil design, workpiece positioning, cooling conditions and operating parameters.

Engineering Selection Guide

Correct equipment selection begins with the workpiece and its heating requirements.

The power supply, induction coil and production process must be engineered together.

Step 1: Identify the Workpiece Material

Specify the material grade, electrical and thermal properties, and any relevant metallurgical requirements.

Step 2: Determine Workpiece Dimensions

Provide the complete dimensions, weight and required heating zone.

The effective heated mass may differ from the total component mass when only a localized region is heated.

Step 3: Define the Required Temperature

Specify the initial temperature and target process temperature.

For brazing, the required temperature depends on the selected filler metal. For hardening, the required temperature depends on the steel grade and treatment process.

Step 4: Calculate Theoretical Heating Energy

For a simplified sensible-heating calculation:

Q = m × Cp × ΔT

Where:

• Q = Thermal energy, kJ.
• m = Effective heated mass, kg.
• Cp = Approximate mean specific heat capacity, kJ/kg·K.
• ΔT = Temperature increase, K.

Step 5: Engineering Calculation Example

Consider an illustrative copper joint assembly with an effective heated mass of 0.25kg.

Assume the joint is heated from 25°C to 725°C, using an approximate mean specific heat capacity of 0.42kJ/kg·K.

The theoretical thermal energy is:

Q = 0.25 × 0.42 × 700 = 73.5kJ

This is equivalent to approximately 0.0204kWh of useful thermal energy.

Step 6: Heating Time and Power Relationship

For the same theoretical thermal energy, the required average useful thermal power increases as the heating time decreases.

Engineering Qualification: These values are theoretical estimates, not measured DW-HF-25 performance. They do not establish that the machine can deliver a particular heating cycle. The assumed 50% electrical-to-workpiece efficiency is for comparison only.

The published 25kVA maximum oscillating-power rating must not be directly compared with the calculated useful thermal power without establishing the actual power-rating definition.

Step 7: Evaluate Coil Geometry

Select a coil that matches the workpiece dimensions, heating-zone shape, electrical matching requirements and available mechanical clearance.

Step 8: Confirm Electrical Requirements

Verify the three-phase power supply, full-load input current, power factor, voltage tolerance and electrical protection.

Step 9: Confirm Cooling Requirements

Obtain the manufacturer’s required water flow, inlet pressure, temperature limits, water quality and cooling protection requirements.

Step 10: Validate the Application

For industrial production, perform a representative application test using the actual material and workpiece geometry.

Record heating time, temperature, loaded frequency, input power, cooling conditions and applicable quality results.

Published HLQ Brazing Application Reference

HLQ has published a separate induction brazing application involving copper tubing and a DW-UHF-10kW induction system.

The reported test used heavy-wall 5/16-inch copper tubing and an available split laboratory coil. The brazing alloy flowed after approximately 5.0–5.2 seconds of heating, with a reported temperature reference of approximately 815°C.

This example illustrates the importance of coil design, joint preparation and heating-cycle control.

It does not establish that a DW-HF-25 will reproduce the same heating time.

For the original test details, review the induction brazing copper tubing case study.

Recommended Factory Acceptance Test

Advantages and Limitations

Advantages of DW-HF-25 High Frequency Induction Heating Equipment

Limitations and Engineering Considerations

Why Choose HLQ?

HLQ Induction Equipment Co., Ltd. provides industrial induction heating equipment for brazing, hardening, annealing, forging, melting and other metalworking applications.

The DW-HF-25 series offers a split-type high-frequency heating arrangement for suitable industrial workstations.

Application-Based Equipment Selection

Equipment selection can be based on material properties, workpiece dimensions, heating temperature, required production rate and available electrical supply.

High-Frequency Induction Power Supply

The DW-HF series includes different power classes for localized industrial heating applications.

The appropriate generator should be selected according to the actual load and process conditions.

Custom Induction Coil Design

Different workpieces may require different induction coil geometries.

Coil design should account for the operating frequency, electrical matching, coupling distance, cooling and mechanical clearance.

Industrial Heating Applications

The equipment can be evaluated for copper tube brazing, carbide tool joining, suitable steel hardening, annealing, and thermal assembly.

Engineering Testing

For production applications, representative heating tests help verify the required cycle time, temperature distribution and process quality.

10 Core FAQs

1. What is the DW-HF-25 high frequency induction heater?

The DW-HF-25 is an industrial high-frequency induction heating system designed for localized heating of electrically conductive metal components. Typical applications include brazing, surface hardening, annealing, shrink fitting and preheating.

2. What is the rated power of the DW-HF-25?

The original product page lists a maximum oscillating-power rating of 25kVA. The actual input active power, output power and useful heating power should be confirmed for the supplied configuration.

3. What electrical supply does the DW-HF-25 require?

The target product page specifies three-phase 380V, 50/60Hz electrical input. Exact voltage tolerance, full-load input current and protection requirements must be verified before installation.

4. What is the operating frequency?

The target page lists 30–80kHz. Other legacy HLQ information includes a 20–80kHz range for certain DW-HF-25 configurations. The actual frequency range should be confirmed from the specific equipment datasheet.

5. Can the DW-HF-25 braze copper tubes?

Yes, it can be considered for suitable copper tube and fitting brazing applications. Actual performance depends on tube dimensions, joint mass, filler metal, coil design and required heating time.

6. Can the DW-HF-25 harden steel shafts?

It can be considered for localized hardening of suitable steel components. The achievable hardness and case depth depend on steel composition, operating frequency, heating time, temperature distribution and quenching.

7. Does the DW-HF-25 require cooling water?

Yes. The equipment uses water cooling for designated electrical and induction coil components. Water flow, pressure, temperature and quality requirements must be confirmed for the actual configuration.

8. Can the DW-HF-25 operate continuously?

The target product page claims 100% duty at 30°C, while another HLQ product page lists 80% duty at 30°C. The continuous-duty capability must therefore be verified under defined electrical, cooling and ambient conditions.

9. Can different induction coils be used with the machine?

Yes, compatible induction coils may be used for different workpieces and applications. Each coil must satisfy the electrical matching, mechanical clearance and cooling requirements of the heating system.

10. How is the correct induction heating machine selected?

The correct machine is selected according to the material, workpiece dimensions, effective heated mass, target temperature, required heating time, operating frequency, available electrical supply and cooling conditions. Engineering calculations and representative application tests provide the basis for final selection.

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