技術資料＞“Own & Operate”-LPC/HPGQ-Heat Treat Services for Automotive Components

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技術資料
Technical Data

“Own & Operate”-LPC/HPGQ-Heat Treat Services
for Automotive Components
Dr. Volker Heuer＊, Dr. Klaus Löser＊概要

精密部品の焼入処理は何十年にわたって雰囲気バッチ炉にて油冷却されていたが近年，真空浸炭処理及び真空高圧ガス焼入（LPC／HPGQ - Process）が燃料噴射用部品あるいは最新のトランスミッションの構成部品の熱処理に最適な処理技術となっている。ALD vacuum technologies社では顧客向けの設備納入のみならず，14年前から顧客の外部委託のニーズに応える為，熱処理の受託事業（Own & Operate）を展開している。精密部品メーカは自社内に熱処理設備を保有して社内処理するか，外部委託する方法のいずれかを選択できる。顧客にとって熱処理の外部委託はユーティリティ設備を含めた熱処理設備の投資が不要であるばかりか，設備の操業，保守点検，試作から解放され開発費用も掛けずに要求を満たす品質を手にすることができる。真空浸炭技術は粒界酸化や表面脱炭の心配が不要，浸炭処理速度が速い，処理歪が少ない，処理後の表面状態がクリーン，環境負荷が低い，生産ラインへの組込みが容易など数多くの特長を有するのみならず，燃料噴射ノズルのような複雑な形状の部品にも均一な浸炭を可能にしている。本稿では，真空浸炭処理を外部委託する場合のメリット，デメリットを含め，当社の受託事業における処理品の品質確保の事例を紹介し，熱処理事業への取組みを紹介する。

1．Introduction
For decades, manufacturers of precision parts usedatmosphere batch furnaces with integral oil quenches for thecase hardening process.

In recent years, low pressure carburizing (LPC) and highThis paper discusses the pros and cons of outsourcing theLPC heat treatment. It presents insight into the technology ofthe equipment and the LPC/HPGQ-process. Finally, ways andmeans how to assure quality of the treated parts are briefly
described.

2． LPC/HPGQ-heat
treatment technology

pressure gas quenching (HPGQ) have become a preferredtechnology for fuel injection components and transmissions fornext generation such as double clutch transmissions or 6/8 speed
automatic transmissions.

LPC is a case hardening process which is performed in aThe manufacturers have the options to either heat treat

pressure of only a few millibar in a protective atmosphere. Intechnologies is offering both furnace equipment for inhouseadvantages of LPC compared to conventional gas carburizing

inhouse or to outsource the heat treatment. ALD vacuum
treatment as well as service-centers for the outsourcing of heattreatment.

most applications acetylene is used as a carbon source. The
are:2013 年 11 月 1 日受付＊R&D Vaccum Heat Treatment, ALD-Vacuum Technologies GmbH, Hanau, Germany

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電気製鋼 第 84 巻 2 号 2013 年① No intergranular oxidation and no surface decarburization

3．Furnace technology③ Higher carburizing temperatures leading to significantly

In 2001, ALD introduced the ModulTherm Ⓡ system. This

② Faster carburizing andshorter cycle times.

concept in equipment is a system that connects up to 12

LPC is usually combined with HPGQ. During HPGQ, theload is quenched using an inert gas-stream instead of a liquid

quenching media. Usually nitrogen or helium are used as aquench gas.

The benefits of HPGQ compared with liquid quench arenumerous:

external quench chamber which moves on a rail system. Thesystem is extremely flexible allowing different processes tobe active at the same time, all utilizing a common quenchsystem.

Since the system is modular, the manufacturer can startwith as few as two vacuum treatment chambers and expand① Reduced distortion in most applications② Clean surfaces after heat treatment (even in blind holes)③ Environmentally friendly with no post washing of parts
required④ Heat treatment can be integrated into the production line.
Fig. 1 depicts a schematic overview of LPC and HPGQ

process.

independent vacuum treatment chambers with a transfer and(up to 12 per system) as his volume dictates. When volume

drops, the equipment can be idled without affecting otherunits. Units taken off line can be kept under vacuum so they

are ready to go when needed. Likewise should maintenancebe required only the affected cells are taken off line and the
production process continues 1).

More than 30 ModulTherm Ⓡ systems comprising 150

treatment chambers have been commissioned worldwide. (Fig.
2 shows ModulTherm Ⓡ . )Fig.1. LPC and HPGQ process (schematic process cycle).

技術資料＞“Own & Operate”-LPC/HPGQ-Heat Treat Services for Automotive Components

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Fig. 2. ModuleTherm Ⓡ plant for LPC and HPGQ process.

4．Heat treatment services forprecision parts
Since ca. 14 years ALD vacuum technologies is offering

besides furnace equipment for inhouse treatment as wellglobal resource centers for the outsourcing of heat treatment.

This business concept introduced as“Own & Operate”
focuses on the transmission-and injection-industry, where
ALD performs heat treatment for the customer as a service

provider. Thus the customer profits from the furnace
manufacturer’s long-time heat treatment know-how andproﬁts from the previously described advantages of LPC andHPGQ without taking ﬁnancial and technical risks.

the furnace manufacturer to the O & O service companies
leads to a steady improvement in productivity and quality as
well as to reduced costs, see Fig. 3.

Once a gear manufacturer has decided to apply LPC andHPGQ, he must decide whether to perform in-house heat
treatment or to outsource the heat treatment to a service
provider. The advantages of outsourcing of heat treatment are:

① No investment in heat treatment equipment and therequired infrastructure② No additional staff to conduct heat treatment operations,laboratory or maintenance③ Access to the latest state-of-the-art heat treatment
technologies without expenditures for development

At the same time the furnace manufacturer proﬁts from the④ A certified quality control program tailored to meetto him. Moreover, the continuous transfer of know-how from

⑤ Heat treatment costs are predictable and generally at aservice companies, as process experiences are reported backcustomer requirements
ﬁxed price.

Fig. 3. Know-how exchange between plant manufacturer and service company.

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電気製鋼 第 84 巻 2 号 2013 年

5.

However there are some disadvantages too, such as:

1Internal ring gear

The ring gear is manufactured from material 5130. It has
an external diameter of 167 mm, a height of 28 mm and 89① loss of heat treatment as a core production competenceinternal teeth. The heat treat speciﬁcation is given in Table 2.

② heat treatment can not be integrated into the productionline③ possibly transportation costs and increased inventory

Table 2. Heat treatment specification of internal ring gear.

④ external interface to heat treatment, therefore higher costs

Casehardening depth

0,3 … 0,6 mm

Surface hardness79 … 83 HRA

Core hardness

no requirements

Microstructure

free of carbides

Itemmanagement requirements

resulting from communication and documentation.

Therefore each option must be systematically analyzed todecide if the outsourcing of heat treatment is an advantage forSpec.

all parties involved.

max. 30 % residual austenite on
tip of toothfacilities in USA, Mexico and Germany. Table 1 shows thefree of bainite until 0.2 mmfrom surface

Currently ALD operates three“Own & Operate”-operating facilities.

Distortion(geometry after heattreatment)

5． Application of technologies
The analysis of two practical applications in a high volume

max roundness: 130 microns
after heat treatment
max. lead variation: 70 microns
after heat treatment

The specific challenge in the heat treat process was toenvironment are good case studies for the value of thecontract services available.

reduce distortion in such a way that subsequent machining

Application 1: Internal Ring Gear of a six speed

operations could be entirely eliminated. As a result oftransmission

extensive development in the quenching process and the use

Application 2: Nozzle for a diesel fuel injection systemof specialized CFC- ﬁxtures it was possible to meet the design
intent.

Table 1. Own & Operate-companies.

Vacuheat GmbH
Limbach-OberFrohna,
Germany
ALD-TT Port Huron,MI, USAALD-TT Ramos Arizpe,
MexicoFoundedCustomer

1999

Continental,
Bosch,Behr

2005

GM, Magna
SystrandContinental

2008

GM, Delphi,
Magna,
Linnamar

Number ofemployees
2012

45

165

100

Number of
installed
treatment
chambers

Number of treated parts per year33

20 million(mainly gear components)

41

30 million(mainly gear components)

20

17 million(mainly gear components)

技術資料＞“Own & Operate”-LPC/HPGQ-Heat Treat Services for Automotive Components

145

Fig. 4 depicts a light weight fixture design which

The internal ring gears have been in continuous production

demonstrated signiﬁcant stability at high temperatures. When

since 2006. After the incoming goods inspection, the ringcompared to traditional alloy ﬁxtures the CFC demonstrated

gears are cleaned in a spray washing machine, followed

no deflection or distortion after many subsequent years of

by LPC using acetylene and HPGQ using helium anduse. By using cfc-ﬁxturing it is guaranteed that all ring gears“ Dynamic quenching”. After tempering, the metallurgicalare always lying horizontally which helps to reduce heatand geometrical quality is examined in the laboratory. This istreatment distortion.

followed by deburring by means of shot blasting and then by
conservation with an antirust agent.
The customer was able to achieve the design intent byeliminating all machining operations of the rings gears
after LPC/HPGQ utilizing the special fixtures and quench
methodology. Subsequent testing and monitoring over a twoyear period progressively demonstrated that conformance andquality inspection was reduced accordingly.

5.
Fig. 4. CFC-fixturing for internal ring gear.
Furthermore, distortion values were significantly reduced
through the use of“ Dynamic quenching”, where the quench
intensity is varied to minimize distortion 2).
Fig. 5 shows the distortion values. The roundness of thering gears in the green state already shows an average of30 micrometers. The roundness values after heat treatment
on an alloy fixture using standard gas quenching were far
beyond the specified requirement of 130 micrometers. Thevalues improved considerably when the CFC-ﬁxture (graphite2Nozzle for diesel injection
system with piezo technology

The nozzle is made of 18CrNi8 material. Fig. 6 shows thespecification of the nozzle after heat treatment. The special
challenge during the casehardening of this nozzle is toguarantee homogeneous carburizing despite of the complex
shape. The component requires tight control with carburizing
evident in the blind hole while at the same time partial
overcarburizing must be prevented as for example in the areaof the so-called“ island ”.

fixture) was used. However only through the application of“Dynamic quenching”and the use of the CFC-fixture thespeciﬁed roundness-values could be met 3).

Fig. 5. Roundness values of internal ring gears before
and after heat treatment.

Fig. 6. Specification of nozzle for diesel injection systemwith piezo technology.

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電気製鋼 第 84 巻 2 号 2013 年

The nozzles are treated with LPC utilizing acetylene andwas shot-blasted. Consequently complete traceability of all

carburizing are covered. The components are austenitized

On request it is possible to equip the ModulThermⓇ system

gas quenched with nitrogen. Areas which do not require

process steps is assured.

twice and quenched twice to increase fatigue strength. This

with a digital camera. The camera is installed at the furnace

any retained austenite into martensite and then followed bystored in a data base in order to visually document the load set

is followed by a deep freezing step at -100 ℃ to transform

tempering. Fig. 7 shows the measured hardening profile atvarious measuring points.

6．Quality control
The quality control of the“Own & Operate”-facilities

entrance and takes photos of each load. These pictures are
up of each batch.

Furthermore the plants are also equipped with an integrated

process control, called“Process-Monitoring”which monitors
all relevant process parameters such as temperature, process
gas ﬂows, cycle times etc.

After the heat treat process, speciﬁc parts from each load

is based on an ERP-system (Enterprise Resource Planning)are examined in the metallurgical laboratory. Parts whichAssurance). which records all quality-data. For each load ainspected after heat treatment by a CNC measuring machine.

with an integrated CAQ-system (Computer Assisted Quality“production traveler”is printed and this production traveler
runs together with the load through all the operations.

Barcodes for each operation are printed on the production

traveler. The barcodes are scanned in each work-center andthe information is stored in the ERP-system indicating thetime and the work-center where the load was treated. Thus it

is possible to retrace exactly when a load was washed, whenand in which furnace it was heat treated and whether a load

are especially prone to distortion can be geometrically
All measured values from the laboratory are entered into theCAQ-system. Upon entering the values, the software veriﬁes

whether the entered values meet the parts specification. If avalue is out of speciﬁcation an error is recorded. Then the load
is stopped and quarantined. Additionally an internal complaintis created in order to detect the root cause of the error and toinitiate a counter-measure.

Fig. 7. Hardness profile for various measuring points on nozzle (x-axis in inches).

技術資料＞“Own & Operate”-LPC/HPGQ-Heat Treat Services for Automotive Components

7．SummaryIn addition to heat treatment plants for Low PressureCarburizing (LPC) and High Pressure Gas Quenching (HPGQ)
ALD Vacuum Technologies has been offering heat treatment
services, called“Own & Operate”, for the past 14 years.

Once a manufacturer of precision components has decided
to apply LPC and HPGQ he has the option to either invest ina heat treatment-plant and to treat in-house or to outsource
heat treatment to a service provider. The advantages anddisadvantages of outsourcing were discussed.

Furthermore the heat treatment technologies used in“Own& Operate”-facilities were introduced by two examples. Since
2006, the use of CFC-ﬁxtures and the application of“DynamicQuenching”allow to caseharden an Internal Ring Gear fora 6-speed-automatic transmission with minimum distortion,

making subsequent machining-operations unnecessary. The
second example showed the casehardening of a nozzle fora diesel injection system. The special challenge during thecasehardening of this nozzle is to guarantee homogeneous
carburizing despite of the complex shape of the part.

The quality control system of the“Own & Operate”-service companies was brieﬂy introduced.

References1 ) L ö s e r, K . , R i t t e r, K . : B e t r i e b s e r f a h r u n g e n m i t
modularen Vakuum-Wärmebehandlungs-anlagen in derAntriebstechnik. In: elektrowärme international, Heft
3/2007, page159-164

2) Heuer, V., Löser, K.: Entwicklung des dynamischen
Abschreckens in Hochdruck-Gasabschreckanlagen. In:Mat.-wiss. u. Werkstofftech. 34 (2003), page 56-63

3) Löser, K., Heuer, V., Faron, D.R.: Distortion Control by

Innovative Heat Treating Technologies in the AutomotiveIndustry, Z. Werkst. Wärmebeh. Fertigung 61 (2006) 6,page 326-329

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