U.I. Engineering




















Product name: Heating and Convective HEATING. 
Brand name: 
Short Description: The convective Heating more Effectively
Breaks Down stresses that are Present in The part [caused
by The Manufacture of The Steel / Semi-Finished Product and
Cutting / shaping Work. ] due to the more uniform heating.
This is a pre-requisite for low distortion heat treatment.

Product name: Air hardening with salt (Bright Hardening). 
Brand name: 
Short Description: Neutral Molten Salt, Durferrit
GS540/R2 by Degussa, Covers The Works throughout
Heating Works Against decarburization and Scaling
up and protects.

Product name: hardening by flame (Flame Hardening). 
Brand name: 
Short Description: Flame hardening is One of Surface
hardening Process, in which A thin Surface Shell of Steel or
Cast Iron is Heated Rapidly to Austenite by HIGH Temperature
Flame. of mix gas of propane and oxygen, then quickly
be quenched to get high hardness.

Product name: HIGH - PRESSURE GAS quenching 
Brand name: 
Short Description: The Simple, Environmentally
favorable, and economical Vacuum Heat Treatment
with Gas quenching under nitrogen (N2) up to pressures
of 10 Bar ABS. has its applications engineering limits.
These limits lie in the hardenability of steels with low
alloy contents, the part dimensions, the number of
pieces in the charge, and the combination of these factors.

Product name: Hardness and residual stress 
Brand name: 
Short Description: Quenching Hardness Carbon
content of material depends on Not on hardenability of it.


Product name: hardening with Doug in length. (Induction) 
Brand name: 
Model: Hardening steering Shaft Motor 
Short Description: Surface Layer of Work-Piece
Can only be Heated by Electro-Magnetic Induction.

Product name: Estimation Hardness of Core 
Brand name: 
Short Description: -

Product name: to measure the depth of the skin 
Brand name: 
Short Description: Quality of carburized part
is usually specified by Both Surface Hardness and Case depth.

Product name: durferrit advantages of carburizing racing. 
Brand name: 
Short Description: Carbon potential of Salt Can be easily
controlled, thus Carbon Concentration by carburizing
Can be easily obtained.

Product name: Carburizing (Carburizing Racing). 
Brand name: 
Short Description: Carburizing is A Remarkable
Method of Enhancing The Surface Properties of shafts,
gears and Machine Parts Other highly stressed.

Product name: hardness and the depth of the skin. 
Brand name: 
Short Description: Characters of Surface of Product
is mainly affected by White Layer.

Product name: tools and our 
Brand name: 
Short Description: -

Product name: a corrosion resistant by QPQ. 
Brand name: 
Model: Tufftride Short Description: By applying Tufftride
QPQ Process, corrosion Resistance is dramatically improved.
To determine The corrosion Resistance of Sample and Component,
A Salt Spray Test (German Standard DIN 50021. ) and a total
immersion test (DIN 50905) are often carried out.

Product name: Tufftride QP, QPQ 
Brand name: 
Short Description: Process is very Quick compared
with The Other nitriding Process in Case of Both
Small or Large Lot production.
Product name: The nitriding furnace with salt. 
Brand name: 
Model: Tufftride Short Description: The Process is carried out in
A subcritical (510 ~ 580oC) bath, Where Small amount of Carbon
and nitrogen are diffused Into The Surface of Component and
conform E-Iron Compound Layer on Surface of Component.

Product name: Steel HSS 
Brand name: 
Short Description: Base Metal Oxide Film on
bursts and be removed by Vacuum and Metal
Wall Gets Wet with Alloy Brazing which enables good.

Product name: Steel HSS 
Brand name: 
Short Description: High Speed ??Steel, as it shown in its
name, has developed for Cutting tools which Can Keep
HIGH Hardness Even if Temperature of tools Come up
Into Red Condition by HIGH Speed ??Cutting. For this purpose,
austenitizing must be. carried out at 1200oC for high hardness.

Product name: steel, cold work tool 
Brand name: 
Short Description: Not Retained austenite may
be avoided by quenching this Kind of because
of HIGH Carbon Steels and alloyed Elements.

Product name: Hot work tool steel 
Brand name: 
Short Description: Though hot Work alloyed
Tool Steels have good hardenability and be Enable
to Harden by Gas quenching in Vacuum Process, as
The size of Mold become larger Recently, Early
Cracking problem has Reported and quenching
Speed ??has been to be discussed. .

Product name: Heat treatment with heat. Tool steel, high mix 
Brand name: 
Short Description: Hardening of Tool Steels alloyed HIGH
have to be carried out in Way of Vacuum Process, in Order
to Prevent any oxidation and decarburization.

Product name: Process Alternate way of plating 
Brand name: 
Short Description: In Process quenching, it is said

that Steel has to be quenched as Fast and slowly as possible.
Product name: plating process Marquez Fishing 
Brand name: 
Short Description: In Case of Large Parts with Complicated
Shapes and Sections, Rapid quenching may Lead to crack
and / or Serious Distortion on Work Piece. 
Product name  :  Process Convection heating by 
Brand name: 
Short Description: Heat Transfer Takes Place by Radiation
only in Vacuum, which is ineffective at Lower than 500 ° C and
Develop Large Temperature difference between Surface and
core of Work Piece. Such Temperature difference should
Make Thermal Stress, which Might Cause some.
distortion of work piece.

Product name: Technical data of the stove VKNQ. 
Brand name: 
Short Description: Charge Weight 500 Kgs Max Rated Temp.
1,300 ° C Max Temp. Uniformity <+ - 5 oK Quenching N2
Gas 6 ~ 10 Bars Vacuum 10 -2 ~ 10. -5 mbars Manufactured
by ALD (Germany).
Product name: advantages of a heat treatment
furnace with vacuum. 
Brand name: 
Short Description: Bright Surface decarburization No.
No. Reproducibility Distortion Minimized oxidation. 




















001 002 003 004 005 006 007 008 009 010 011 012

013 014 015 016 017 018 019 020 021 022 023 024







  • Bright surface
  • No decarburization
  • No oxidation
  • Minimized distortion
  • Reproducibility
  • Vacuum high temperature brazing
  • Economical

Working Space 600x600x900 mm

  • Charge Weight 500 Kgs max
  • Rated Temp. 1,300 oC max
  • Temp. Uniformity < + - 5 oK
  • Quenching N2 Gas 6~10 bars
  • Vacuum 10 -2 ~10 -5 mbars
    Manufactured by ALD (Germany)

  • Heat transfer takes place by radiation only in vacuum, which is ineffective at lower than 500 oC and develop large temperature difference between surface and core of work piece. Such temperature difference should make thermal stress, which might cause some distortion of work piece.
  • By adding N2 gas of 2 bars for heat convector, homogeneous and rapid heating can be achieved.


  • In case of parts with large sections and complicated shapes, rapid quenching may lead to crack and/or serious distortion on work piece.
  • By programmed controlling quenching above Ms point of material by using two thermocouples installed on surface and core of a dummy with charge, minimized distortion can be achieved.
005 PROCESS Reversible Direction


  • In quenching process, it is said that steel has to be quenched as fast and slowly as possible.
  • The former is for enough cooling speed to obtain ideal micro structure, the latter is for prevent cracking and severe distortion of work.
  • Our furnace makes both available by high pressure gas quenching, by programmable reversible cooling and by Marquenching
006 Concept Heat Treatment of HIGH ALLOYED TOOL STEELS

  • Hardening of high alloyed tool steels have to be carried out in way of vacuum process, in order to prevent any oxidation and decarburization.
  • In our vacuum process, a dummy block of which diameter is equivalent to the control section of work piece to be hardened. Two thermocouples installed at both core and surface of the dummy can manage the temperature control of work piece at both surface and core throughout its hardening procedure. By this way we are able to ; -
  1. manage any thermal stress which may arise while heating work piece up and minimize any distortion.
  2. prevent insufficient austenitizing of core and over solution of carbides through austenitizing by controling austenitizing by core temperature.
  3. apply marquenching procedure in order to prevent cracking and minimize any distortion by both thermal and transforming stress in case of complicated shape work piece.
    Three high temperature temperings are to done as general rule. The first temper is for decomposing retained austenite which is unavoidable in high carbon and high-alloyed tool steels. By the second tempering we control hardness required. The third tempering is stress relieving to prevent any cracking and deforming through the subsequent process.
007 Hot work Alloyed Tool Steel

  • Though hot work alloyed tool steels have good hardenability and be enable to harden by gas qu enching in vacuum process, as the size of mold become larger recently, early cracking problem has reported and quenching speed has been to be discussed.
  • According to CCT curve left, bainite transforms in earlier stage than pearlite and it will accompany some amount of retained austenite in matrix. Carbides precipitated on boundary of austenite by tempering are considered the cause of early cracking.
  • In our vacuum process, quenching nitrogen up to 10 bars can be used and can increase effective quenching speed by alternative direction quench program. Thus we will try to reduce bainite, intending long life mold making.
  • We also recommend the late bainite transform type steels recently announced.
008 Cold Work Alloyed Tool Steels

  • Retained austenite may not be avoided by quenching this kind of steels because of high carbon and alloyed elements.
  • Retained austenite often causes cracking or distortion of work piece in subsequent wire cut or grinding, subzero treatment or 2 times high temperature tempering are recommendable.
  • By high temperature tempering, hardness specified shall be HRC55~58. When HRC60 is needed, austenitizing temperature must be applied 1070oC that is higher than usual one of 1030oC, in order to harden by second hardening. This process is not recommendable because it increases retained austenite.
  • Further stress relieving is to be carried out for any subsequent machining process
009 High Speed Steels

  • High speed steel, as it shown in its name, has developed for cutting tools which can keep high hardness even if temperature of tools come up into red condition by high speed cutting. For this purpose, austenitizing must be carried out at 1200oC for high hardness.
  • Tempering shall be carried out more than 3 times, as this steel has a lot of retained austenite after quenched.
  • Thin cutting tools can be straightened taking an advantage of existing retained austenite after quenched while warm.
  • High speed steel may be used in room temperature and instead high toughness is required. In this case, austenitizing shall be lower than usual. The pocess for high toughness is called as under hardening.

010 Vacuum high temperatureAdvantageous BRAZING

  • Oxide film on base metal bursts and be removed by vacuum and metal wall gets wet with alloy which enables good brazing.
  • By heating the work piece to high temperature in vacuum, enough diffusion is available between metals and good bonding with no inclusion nor gas hole can be attained.
  • Very narrow brazing gaps of less than 0.05mm makes bonding metals with high strength and good accuracy.



011 TD PROCESS VC hard coating
         Extremely high Vanadium carbile can be applied on steel substrate by TD PROCESS. The layer 
improves resistance against  wear, scuffing, oxidation ,corrosion and etc. Of steel products. Since the 
process was invented by Toyota Central Research and Developement Laboratories, it has been used 
for long period in worldwide  automobile industrie and other many field of industries.

           The substrate material be immerged  into a high
 temperature   salt   bath  containing    vanadium.    The 
vanadium    in   sult   is to  form  VC    (vanadium carbile) 
with   carbon in  substrate  steel  which is diffused  to the 
surface of work.The principle of this process is followed
by   hardening  and   tempering   in  order  to  attain   the 
mechanical   properties required for substrate material.
This  process  can  be  applied on any substrate  steel  containing     carbon   of   0.3%    and  more.   In  case of 
substrate of  less than  0.3%  carbon ,  precarburizing is recommended.
           Hardness   obtainable   by  this   process  will  be 
3000   Vickers  Hardness ,  which  is ,  needless  to  say, 
harder than  any  kind of  nitrided  tool steel, high speed 
steel.    It  is  harder than  tunsten  carbile  coating, hard 
chrome plating  and  ultra  hardness  steels.   As the VC 
layer of this   process    ismadeby   diffusion   of  carbon   
from substrate ,the layer adhered  to the substrate  work 
pieces and never peel out even  used in hard working. 
            The VC layer also shows excellent anti corrosion characteristics.

012 Sequence of TD Process

014 Tufftride QP, QPQ


Tufftride is a salt bath nitriding process by Dufferit in Germany, and has been in use in a wide range of industries.

  • The process is carried out in a subcritical (510~580oC) bath, where nitrogen and small amount of carbon are diffused into the surface of component and conform e-iron compound on surface layer of component.
  • The hardness of compound layer, ranging from 400 to 1200 HV depending on the base material used, is responsible for fatigue, wear and galling resistance
015 Examples of Application

  • Hot work tools : Forging, extrusion, die casting mould
  • Cold work tools
  • High speed steel tools
  • Crank shaft, Cam shaft
  • Cylinder liner, block & head
  • Gears
  • Diesel engine valve
  • Plastic injection screw & barrel
  • Food processing equipments & tools
  • QP is the liquid soft nitriding process applicable for any kind kind of steel.
  • Process is very quick compared with the other nitriding process in case of both small or large lot production.
  • High surface hardness obtained by theis process, makes tool life longer.
  • QPQ is an oxidizing cooling process by using special salt of AB1, after QP process is done.
  • By applying QPQ treatment, corrosion resistance will be much improved along with wear resistance




016 Hardness and Case depth

Nitrided layers by Tufftride process consists of white layer (compound layer) and diffusion layer

  • Characters of surface of product is mainly affected by white layer.
  • Surface hardness and thickness of both layers depend on the material used and on nitriding duration.
  • Figures right are quoted from Bohler book. 
017 Our Facilities


Ø 500 x 750 mm
Ø 710 x 1500 mm
Ø 1000 x 1500 mm


    Ø 1000 x 1500 mm

018 Corrosion Resistance by QPQ


 By applying Tufftride QPQ process, corrosion resistance is dramatically improved.

     To determine the corrosion resistance of sample and component, a salt spray test (German Standard DIN 50021) and a total immersion test (DIN 50905) are often carried out.

     The under figure shows the result of a salt spray test by a 5% salt solution at 35o C on both hard chrome plated piston rod and Tufftride QPQ treated carbon steel bars. After 40 hours, the first corrosion spots occurred on the chrome plated piston rods. After 180 hours, the chrome plated rods showed very heavy corrosive attack over a large area. The QPQ treated rods, however, showed no sign of corrosion.



019 What’s CARBURIZING ?

  • Carburizing is a remarkable method of enhancing the surface properties of shafts, gears and other highly stressed machine parts.
  • Low carbon steel of finished shapes are converted by carburizing into a composite consisting of a high-carbon steel case and low carbon steel core.
  • When this composite is quenched to martensite and tempered, the high hardness and strength of the case microstructure, combined with the favorable case compressive residual stress developed by interaction between the case and core during quenching, produce very high resistance to wear, bending fatigue, and rolling-contact fatigue.

020 Advantages durferrit carburizing
  • CEconstant80 is the patent salt by Durferrit(Germany).
  • Carbon potential of salt can be easily controlled, thus carbon concentration by carburizing can be easily obtained.
  • Through carburizing process, small amount of nitrogen is also induced with carbon. (Carbo-nitride)
  • Carbo-nitriding be managed by treating temperature.
  • Direct quenching at carburize temperature will minimize distortion.
    Economical and quick for even small amount production.



021 Measurement of case depth
  • Quality of carburized part is usually specified by both surface hardness and case depth.
  • Case depth is defined as effective case depth and total case depth. It shall be clearly specified at order.
  • 'Effective case depth’ is a distance from surface to specified hardness, if not specified, HRC50 is used.
  • ‘Total case depth’ is a distance from surface to the position where difference between original matrix cannot be detected by any of chemical etching or hardness check.

022 Estimation of CORE HARDNESS


            The estimation of internal hardness of carburize part is available by using the jominy carve of the material. Select quenching media water or oil, select the portion of hardness required sush surface, ¾from center or center, and then chose the actual diameter of round bar. The hardness can be estimated 
at  the  crossing  point  of  the  ine draw down  from  a  diameter and the jominy carve of the material. The surface hardness means uncarburized surface.


023 Bright Hardening by Salt Bath

  • Molten neutral salt, Durferrit GS540/R2 by Degussa, covers the works throughout heating works up and protects against decarburization and scaling.
  • Taking out the works out of salt, thin film of salt is covering surface of work pieces, pre-venting decarburization and scaling. The film is easily pealed out in quenching media not disturbing rapid cooling.
  • As the heat mass of the salt bath is huge, work pieces can be heated and equalized 3 times as quick as other furnace, and suitable for both small and mass production.
  • The salt bath is daily quality controlled by deslugging and checking decarburization using some high carbon steel wire.

  • Through quenching, both thermal and transformation stresses arise by temperature difference between surface and core of complicated work piece. Those stresses might cause crack or distortion of work piece.
  • In order to prevent these ploblems, the work piece has to stop cooling at just above the transformation start temperature (MS), and then slow cooled. This process is called as "time quenching".
Explanation of time quenching
024 Austempering
         Astempering is the special hardening process by  which the work pieces are quenched into 
    hot  salt  bath and  hold  for  hours to transform(isothermal transform) in order to conform Bainite structure. The Bainite structure has excellent high ductility and toughness compares with those of tempered Martensite by conventional quenching and tempering. The table 1 below show an example  of   mechanical   properties  obtained   by  three   different  process.  This  process is advantageous for minimizing deformation and dimentional changes by hardening.
025 Table 1. Mechanical properties by 3 different hardening process
026 The relationship between hardness and austempering temperature in case of SK5.

  • Surface layer of work-piece only can be heated by electro-magnetic induction.
  • High surface hardness, wear resistance and high fatigue limit can be obtained
  • Compressive residual stress generated by induction hardening brings superior fatigue limit.
  • Process following heat-treatment can be omitted because of little decarburization or scaling of work piece.
  • Quick and economical for small lot production is available.

Quenching spline part of shaft

10KHz 150KW
&O slash;300x2,000 Max
CASE DEPTH 1~5 mm.
200KHz 40KW
Ø 50x600 Max
CASE DEPTH 0.4 ~ 2.5 mm.

  • Quenching hardness depends on carbon content of material not on hardenability of it.
  • Hardness obtained by induction hardening is higher than it by ordinary quenching, because of compressive residual stress generated by the process.
  • While maintaining hardness and residual stress, tempering is to be carried out in order to prevent deforming, grinding crack and to improve toughness.
Carbon content & quenching hardness
Distribution of hardness & residual stress
Carbon content & tempered hardness
  • For controlling induction hardening, as it is difficult to measure Austenitizing temperature directly, frequency(penetrate depth), power density, ampere and voltage, heating duration are used instead.
  • The lower frequency is applied, the deeper harden depth is obtained.
  • There are two kinds of heating up, those are one shot heating and progressive heating.

Relationship between hardened depth and heating duration, power density and frequency




  • Flame hardening is one of surface hardening process, in which a thin surface shell of steel or cast iron is heated rapidly to Austenite by high temperature flame of mix gas of propane and oxygen, then quickly be quenched to get high hardness.
  • The process has advantages to improve abrasion resistance and fatigue limit by compressive residual stress created by surface hardening as same as induction hardening.
  • The process has no limit of part size and/or weight, and is suitable and economical for small scale production. The cost for making induction coil can be neglected.

  • Flame for hardening shall be neutral. By mix ratio of propane and oxygen of 1.4 must be used for the highest temperature of 2,930oC obtainable.
  • Flame hardening is applicable on any heattreatable steel and cast iron.
  • The higher austenitizing temperature by 20~30oC is suitable.
  • The preheating is recommendable in order to avoid rapid heating and cooling on such work piece as of intricate shape or of gray cast iron which has apprehension of cracking.
  • By preheating the hardened depth can be deeper and also cracking season cracking can be prevented by self tempering effect.
  • Hardness obtainable by this process on cast iron depend on its amount of pearlite in matrix. Pre-normalizing for increasing matrix pearlite is recommendable for the purpose.
Effects of matrix of FCD on flame hardened hardness and depth. 
Response of steel and cast to flame hardening (HRC)
JIS Symbol
Air Cool
Oil Cool
Water Cool
S20C, S35C
33 ~ 50
S38C, S50C
52 ~ 58
55 ~ 60
S53C, S58C
50 ~ 60
58 ~ 62
60 ~ 63
SCM 435
50 ~ 55
50 ~ 60
SCM 440
52 ~ 56
52 ~ 56
55 ~60
SK 3, 4, 5, 6
52 ~ 56
58 ~ 62
62 ~ 65
55 ~ 56
55 ~ 60
62 ~ 64
FC 300
43 ~ 48
43 ~ 48
FC 350
48 ~ 52
48 ~ 52
FCD 600
35 ~ 45
FCD 700
52 ~ 56
55 ~ 60
  • Selection of heat treatment process
  • Selection of material
  • Finding material symbol
  • Selection of available subsidized material,
  • Investigating cause of heat treatment failure
  • Investigation of cause for fracturing in service, advice for prevention measure
  • Longer tool life
  • Consultant for welding
  • Consultant for foundry and forging production
  • Consultant for quality of forged or foundry products
  • Others
Please contact us in 
Tel: 02-708-3670-6
Fax: 02-708-3678


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